Desulfurization solvent, its preparation method and application

Abstract

The application relates to the technical field of natural gas purification, and discloses a desulfurization solvent and a preparation method and application thereof, which are calculated based on 100 wt% of the desulfurization solvent and comprise 1 wt%-20 wt% of a steric amine, 30 wt%-50 wt% of an alcohol amine, 3 wt%-8 wt% of a phosphazene and the balance of water. The desulfurization solvent adopts mutual cooperation of the steric amine, the alcohol amine and the phosphazene, has good selectivity of CO2, high desulfurization efficiency, guarantees the purity and quality of purified natural gas and Claus tail gas, has excellent anti-foaming performance, and guarantees stable operation of the device.

Description

Technical Field

[0001] This invention relates to the field of natural gas purification technology, specifically to desulfurization solvents, their preparation methods, and applications. Background Technology

[0002] Natural gas, as a clean and efficient energy source, occupies an important position in the energy structure. To meet the ever-increasing energy demand, improving the utilization rate and safety of natural gas is crucial. Currently, in natural gas purification, both the desulfurization unit and the subsequent sulfur recovery tail gas treatment unit are acidic gas processes, thus allowing the use of the same amine solvent as the absorbent. However, current natural gas purification desulfurization solvents suffer from drawbacks such as complex multi-component composition, low desulfurization efficiency, and easy foaming of the amine solution. In the tail gas treatment unit, lean amine solution and sulfur recovery tail gas are absorbed through counter-current contact; the semi-rich solution at the bottom of the absorption tower can be sent to the primary absorption tower of the desulfurization unit for cascade use; finally, it is sent to the regeneration tower of the desulfurization unit, and the regenerated lean solution is returned to the sulfur recovery tail gas absorption tower. Cascade desulfurization technology can improve solvent utilization efficiency, and only requires one amine regeneration system, reducing equipment investment and energy consumption. Currently, tail gas cascade purification desulfurization technology is still in its early stages, generally suffering from poor selectivity, easy foaming of the amine solution, and low desulfurization efficiency, especially for organic sulfur, particularly COS removal.

[0003] Patent document CN111925848A discloses a highly efficient solvent for removing carbonyl sulfide, comprising the following raw materials by mass percentage: 20%–50% alkanolamine solvent, 10%–40% special solvent, 1%–6% activator, and 0.2%–3% other additives composed of defoamer, antioxidant, and corrosion inhibitor, with a total mass percentage of 100%. The special solvent is any one of N-thioaldehyde-aminoacetic acid-tert-butyl ester and diethyl thioaminomalonate. The activator is any one of (S)-3-(hydroxymethyl)pyrrolidine and (S)-3-(hydroxyethyl)pyrrolidine. The defoamer is polyether-modified organosilicon. The antioxidant is any one of thiodipropionic acid and naphthalene. The corrosion inhibitor is any one of quaternary ammonium salt, Mannlich base, and imidazoline. The above-mentioned desulfurization solvents still have problems such as complex composition, difficulty in removing organic sulfur, high carbon dioxide co-absorption rate, and easy foaming of amine solution.

[0004] Therefore, there is an urgent need to develop a highly efficient desulfurization solvent that is suitable for both natural gas purification and Claus tail gas with high content of H2S, CO2 and organic sulfur. Summary of the Invention

[0005] The purpose of this invention is to overcome the technical problems existing in the natural gas purification and desulfurization process, such as complex composition of solvents, low desulfurization efficiency, easy foaming of amine solutions, poor selectivity in the purification of Claus tail gas with high H2S, CO2 and organic sulfur content, easy foaming of amine solutions, and low desulfurization efficiency, especially the poor removal effect of organic sulfur, particularly COS. This invention provides a desulfurization solvent, its preparation method and application, which achieves high desulfurization efficiency and selectivity while ensuring the quality of purified natural gas or Claus tail gas, and improves the anti-foaming performance of the desulfurization solvent during application.

[0006] To achieve the above objectives, the first aspect of the present invention provides a desulfurization solvent, comprising, in 100 wt% of the solvent: 1 wt%-20 wt% of a hindered amine, 30 wt%-50 wt% of an alkanolamine, 3 wt%-8 wt% of a phosphazene, and the balance being water.

[0007] In the desulfurization solvent of this invention, the interaction between N and H in phosphazene makes it more readily accept protons, thus exhibiting strong basicity and weak nucleophilicity, resulting in high H2S removal efficiency. Furthermore, due to its strong basicity and unique dendritic structure, phosphazene, in synergy with hindered amines, not only increases the selectivity for carbon dioxide but also acts as a catalyst to promote the hydrolysis of COS into H2S and CO2, significantly improving the COS removal rate. Simultaneously, this solvent also possesses excellent anti-foaming properties, ensuring stable operation of the equipment.

[0008] In some embodiments of the present invention, the desulfurization solvent, based on 100 wt%, comprises: 5 wt%-15 wt% of hindered amine, 35 wt%-45 wt% of alkanolamine, 5 wt%-8 wt% of phosphazene, and the balance being water; preferably, it comprises: 10 wt%-15 wt% of hindered amine, 40 wt%-45 wt% of alkanolamine, 5 wt%-8 wt% of phosphazene, and the balance being water.

[0009] In some embodiments of the present invention, the sterically hindered amine is selected from at least one of 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), 1,5,7-triazidobicyclo[4.4.0]dec-5-ene (TBD), 1,3-bis(tert-butylamino)-2-propanol (DTBP), 1,3-di(dimethylamino)-2-propanol (BDAP), tert-butylaminoethoxyethanol (TBEE), tert-butylaminoethanol (TBE), tert-butylaminodiethoxyethanol (TBDEE), 2-amino-2-methyl-1-propanol (AMP), N,N'-bis(2-hydroxyethyl)piperazine (BHEP), N,N'-bis(2-hydroxypropyl)piperazine (HPP), and 1-(2-hydroxyethyl)-4-(2-hydroxypropyl)piperazine (HEHPP).

[0010] In some embodiments of the present invention, the sterically hindered amine is selected from at least one of 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), 1,3-bis(tert-butylamino)-2-propanol (DTBP), tert-butylaminoethoxyethanol (TBEE), tert-butylaminoethanol (TBE), 2-amino-2-methyl-1-propanol (AMP), and N,N'-bis(2-hydroxyethyl)piperazine (BHEP); preferably 1,3-bis(tert-butylamino)-2-propanol (DTBP).

[0011] In this invention, the hindered amine is selected from at least one of 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,3-bis(tert-butylamino)-2-propanol, tert-butylaminoethoxyethanol, tert-butylaminoethanol, 2-amino-2-methyl-1-propanol, and N,N'-bis(2-hydroxyethyl)piperazine, preferably 1,3-bis(tert-butylamino)-2-propanol. The combination of the above-mentioned hindered amine with phosphazene can further improve the selectivity of desulfurization, especially the removal rate of organic sulfur, and the treatment capacity of carbon dioxide, thereby reducing the solvent circulation volume and improving efficiency.

[0012] In some embodiments of the present invention, the alkanolamine is selected from at least one of methyldiethanolamine, monoethanolamine, diethanolamine, and diisopropanolamine.

[0013] A second aspect of the present invention provides a method for preparing a desulfurization solvent, comprising the following steps:

[0014] Hindered amine, alkanolamine, phosphazene and water are added to a mixer and stirred to obtain a desulfurization solvent.

[0015] In some embodiments of the present invention, the mixing conditions include: a stirring speed of 400-600 r / min and a temperature of 20-30°C.

[0016] A third aspect of the present invention provides the use of the above-described desulfurization solvent or the desulfurization solvent prepared by the above-described preparation method in the desulfurization of natural gas purification or Claus tail gas purification.

[0017] The fourth aspect of the present invention provides a desulfurization method for natural gas purification, wherein sulfur-containing natural gas is contacted with a desulfurization solvent in a desulfurization container to perform desulfurization; wherein the desulfurization solvent is selected from the above-mentioned desulfurization solvent or the desulfurization solvent prepared by the above-mentioned preparation method.

[0018] In some embodiments of the present invention, the contact is a countercurrent contact, the standard volume ratio of the sulfur-containing natural gas to the desulfurization solvent is (300-600):1; the pressure of the sulfur-containing natural gas is 3-8 MPa; and the sulfur-containing natural gas contains 2%-10% H2S and 3%-12% CO2.

[0019] In this invention, during the desulfurization process of natural gas purification, it is necessary to adjust the standard volume ratio of sulfur-containing natural gas and desulfurization solvent. If the standard volume ratio is too low, the desulfurization solvent content is too high, more CO2 gas is absorbed, and the selectivity is poor; if the standard volume ratio is too high, the desulfurization solvent content is low, and the desulfurization efficiency is poor.

[0020] In some embodiments of the present invention, the standard volume ratio of the sulfur-containing natural gas to the desulfurization solvent is (400-500):1; the pressure of the sulfur-containing natural gas is 4-6 MPa.

[0021] The fifth aspect of the present invention provides a desulfurization method for purifying Claus tail gas, wherein sulfur-containing Claus tail gas is contacted with a desulfurization solvent in a desulfurization container to perform desulfurization; wherein the desulfurization solvent is selected from the above-mentioned desulfurization solvent or the desulfurization solvent prepared by the above-mentioned preparation method.

[0022] In some embodiments of the present invention, the contact is a countercurrent contact, and the standard volume ratio of the sulfur-containing Claus tail gas to the desulfurization solvent is (50-600):1, preferably (150-500):1; the sulfur-containing Claus tail gas is at atmospheric pressure; and the sulfur-containing Claus tail gas contains 60-200 ppm H2S, 20-100 ppm COS, and 10%-30% CO2.

[0023] In this invention, during the desulfurization process of Claus tail gas purification, it is necessary to adjust the standard volume ratio of sulfur-containing Claus tail gas and desulfurization solvent. If the standard volume ratio is too low, the desulfurization solvent content is too high, more CO2 gas is absorbed, and the selectivity is poor; if the standard volume ratio is too high, the desulfurization solvent content is low, and the desulfurization efficiency is poor.

[0024] The technical solution of the present invention has the following beneficial effects:

[0025] In the desulfurization solvent of this invention, hindered amines, alkanolamines, and phosphazenes work together to improve the anti-foaming properties of the purified gases while ensuring the purity and quality of the purified natural gas and Claus tail gas. Especially in Claus tail gas purification, simultaneous removal of COS and H2S can be achieved; the COS removal rate is particularly high. Due to its strong alkalinity and unique dendritic structure, phosphazenes synergize with the hindered amines, increasing the selectivity for carbon dioxide and acting as a catalyst to promote the hydrolysis of COS into H2S and CO2, significantly improving the COS removal rate. Simultaneously, this solvent also possesses excellent anti-foaming properties, ensuring stable operation of the equipment. This reduces the solvent circulation volume and improves efficiency, thereby reducing energy consumption and significantly improving economic benefits. Attached Figure Description

[0026] The invention will now be described in more detail with reference to embodiments and the accompanying drawings.

[0027] Figure 1 It is a flow chart of a simulated natural gas or simulated Claus tail gas desulfurization process.

[0028] Figure label:

[0029] 1 – Gas distribution tank; 2 – Simulated natural gas (simulated Claus tail gas); 3 – Absorber; 4 – Lean solution; 5 – Purified gas; 6 – Rich solution; 7 – Rich solution pump; 8 – Heater; 9 – Regeneration tower; 10 – Bottom reboiler; 11 – Lean solution pump; 12 – Cooler; 13 – Top condenser; 14 – Acid gas; 15 – First water separator; 16 – Second water separator. Detailed Implementation

[0030] To make the present invention easier to understand, the present invention will be described in detail below with reference to embodiments and accompanying drawings. These embodiments are for illustrative purposes only and should not be considered as limiting the scope of the present invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the materials used in the embodiments are commercially available products or conventional products that can be synthesized by known methods.

[0031] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0032] In the following examples and comparative examples, the content of each component in the sulfur-containing gas was determined by coulometric analysis and chromatographic methods, and the thiol content was expressed as sulfur.

[0033] After desulfurization, the foaming performance of the amine solution was tested. When the water temperature in the water bath reached 40℃, 20mL of amine solution was taken into a foam height test tube and placed in a constant temperature water bath for 10 minutes. Nitrogen gas was passed through the foam height test tube at a flow rate of 450mL / min for 5 minutes, and the foam height and defoaming time were recorded.

[0034] The present invention will be described in detail below through embodiments.

[0035] Example 1

[0036] 1. Preparation method of desulfurization solvent

[0037] Add 5g of DTBP, 40g of methyldiethanolamine, 5g of phosphazene, and 50g of water to a mixer and stir at a speed of 500r / min at room temperature to obtain a desulfurization solvent.

[0038] 2. Simulated natural gas desulfurization methods

[0039] The simulated natural gas contained 4.1% H2S, 3.9% CO2, and the remainder N2. The pressure of the simulated natural gas was 5 MPa, and the standard volume ratio of the simulated natural gas to the desulfurization solvent was 450:1.

[0040] See the natural gas desulfurization process flow. Figure 1 Simulated natural gas 2, output from gas distribution tank 1, enters the lower part of absorption tower 3 and comes into countercurrent contact with lean liquid 4 entering from the upper part of absorption tower 3. Lean liquid 4 selectively absorbs acidic gas components, yielding purified gas 5. After water separation by the second water separator 16, it is discharged from the top of absorption tower 3. The rich liquid 6, which has absorbed acidic gas components, enters the upper part of regeneration tower 9 through rich liquid pump 7 and heater 8. In regeneration tower 9, it is flash-evaporated and boiled by reboiler 10 at the bottom of the tower, regenerating into lean liquid 4. Lean liquid 4 is pressurized by lean liquid pump 11, sent to cooler 12 for cooling, and then enters the upper part of absorption tower 3 to reabsorb acidic gas components. The acidic gas components regenerated from regeneration tower 9, cooled by condenser 13 at the top of the tower, are then discharged after water separation by the first water separator 15.

[0041] The purified gas contains 1.5 ppm H2S and 2.2% CO2. The foam height is approximately 1.0 cm, the defoaming time is less than 1 second, and the amine solution does not foam.

[0042] 3. Desulfurization method simulating Claus exhaust gas

[0043] The simulated Claus tail gas contained 90 ppm H2S, 38 ppm COS, 18.2% CO2, and the remainder N2. The simulated Claus tail gas was at atmospheric pressure. The standard volume ratio of the simulated Claus tail gas to the desulfurization solvent was 150:1. The simulated Claus tail gas used a desulfurization method and equipment similar to those used for simulated natural gas.

[0044] Neither H2S nor COS was detected in the purified gas, and the CO2 content was 13.8%. The amine solution did not foam.

[0045] Example 2

[0046] The desulfurization solvent was prepared according to the method in Example 1, except that the hindered amine was 5g of AMP.

[0047] The simulated natural gas was desulfurized using the same method as in Example 1. The purified gas contained 4.1 ppm H2S and 0.8% CO2. The foam height was approximately 1.8 cm, the defoaming time was approximately 1.2 s, and the amine solution did not foam. The simulated Claus tail gas was also desulfurized using the same method as in Example 1. Neither H2S nor COS was detected in the purified gas, and the CO2 content was 12.7%. The amine solution did not foam.

[0048] Example 3

[0049] The desulfurization solvent was prepared according to the method in Example 1, except that the hindered amine was 5g of BHEP.

[0050] The simulated natural gas was desulfurized using the same method as in Example 1. The purified gas contained 3.4 ppm H2S and 0.4% CO2. The foam height was approximately 2.0 cm, the defoaming time was approximately 1.5 s, and the amine solution did not foam. The simulated Claus tail gas was also desulfurized using the same method as in Example 1. Neither H2S nor COS was detected in the purified gas, and the CO2 content was 12.4%. The amine solution did not foam.

[0051] Example 4

[0052] The desulfurization solvent was prepared according to the method in Example 1, except that 20g of DTBP and 25g of methyldiethanolamine were added, while the amounts of other components were the same as in Example 1.

[0053] The simulated natural gas was desulfurized using the same method as in Example 1. The purified gas contained 0.9 ppm H2S and 1.5% CO2. The foam height was approximately 1.5 cm, the defoaming time was approximately 2.0 s, and the amine solution did not foam. The simulated Claus tail gas was also desulfurized using the same method as in Example 1. Neither H2S nor COS was detected in the purified gas, and the CO2 content was 11.8%. The amine solution did not foam.

[0054] Example 5

[0055] The desulfurization solvent was prepared according to the method in Example 1, except that 1g of DTBP and 44g of methyldiethanolamine were added, while the amounts of other components were the same as in Example 1.

[0056] The simulated natural gas was desulfurized using the same method as in Example 1. The purified gas contained 5.2 ppm H2S and 2.0% CO2. The foam height was approximately 1.0 cm, the defoaming time was approximately 1 second, and the amine solution did not foam. The simulated Claus tail gas was desulfurized using the same method as in Example 1. The purified gas contained 1.8 ppm H2S, 2.5 ppm CO2, and 14.0% CO2. The amine solution did not foam.

[0057] Example 6

[0058] The desulfurization solvent was prepared according to the method in Example 1, except that 3g of phosphazene and 42g of methyldiethanolamine were added, while the amounts of other components were the same as in Example 1.

[0059] The simulated natural gas was desulfurized using the same method as in Example 1. The purified gas contained 4.1 ppm H2S and 2.5% CO2. The foam height was approximately 1.0 cm, the defoaming time was approximately 1 second, and the amine solution did not foam. The simulated Claus tail gas was desulfurized using the same method as in Example 1. The purified gas contained 4.3 ppm H2S, 5.0 ppm CO2, and 14.5% CO2. The amine solution did not foam.

[0060] Example 7

[0061] The desulfurization solvent was prepared according to the method in Example 1, except that 8g of phosphazene and 37g of methyldiethanolamine were added, while the amounts of other components were the same as in Example 1.

[0062] The simulated natural gas was desulfurized using the same method as in Example 1. The purified gas contained 0.8 ppm H2S and 1.8% CO2. The foam height was approximately 1.0 cm, the defoaming time was approximately 1 second, and the amine solution did not foam. The simulated Claus tail gas was also desulfurized using the same method as in Example 1. Neither H2S nor COS was detected in the purified gas, and the CO2 content was 12.7%. The amine solution did not foam.

[0063] Example 8

[0064] The same desulfurization solvent preparation method as in Example 1 was used, except that the standard volume ratio of simulated natural gas to desulfurization solvent was 600:1 when desulfurizing simulated natural gas. The purified gas contained 63.8 ppm H2S and 2.9% CO2. The amine solution did not foam.

[0065] Example 9

[0066] The same desulfurization solvent preparation method as in Example 1 was used, except that the pressure of the simulated natural gas was 3 MPa when desulfurizing the simulated natural gas. The purified gas contained 32.5 ppm H2S and 2.8% CO2. The amine solution did not foam.

[0067] Example 10

[0068] The same desulfurization solvent preparation method as in Example 1 was used, except that the standard volume ratio of the simulated Claus tail gas to the desulfurization solvent was 600:1 when desulfurizing the simulated Claus tail gas. The purified gas contained 18.2 ppm H2S, 24.0 ppm COS, and 16.9% CO2. The amine solution did not foam.

[0069] Example 11

[0070] The same desulfurization solvent preparation method as in Example 1 was used, except that the standard volume ratio of simulated Claus tail gas to desulfurization solvent was 50:1 when desulfurizing the simulated Claus tail gas. Neither H2S nor COS was detected in the purified gas, and the CO2 content was 7.7%. The amine solution did not foam.

[0071] Comparative Example 1

[0072] The desulfurization solvent was prepared according to the method in Example 1, except that DTBP was 10g and did not contain phosphazenes.

[0073] The simulated natural gas was desulfurized using the same method as in Example 1. The purified gas contained 26.2 ppm H2S and 3.5% CO2. The foam height was approximately 1.0 cm, the defoaming time was less than 1 second, and the amine solution did not foam. The simulated Claus tail gas was desulfurized using the same method as in Example 1. The purified gas contained 15.2 ppm H2S, 6.8 ppm CO2, and 14.5% CO2. The amine solution did not foam.

[0074] Comparative Example 2

[0075] The desulfurization solvent was prepared according to the method in Example 1, except that DTBP was not added and the phosphazene content was 10g.

[0076] The simulated natural gas was desulfurized using the same method as in Example 1. The purified gas contained 19.2 ppm H2S and 3.3% CO2. The foam height was approximately 1.0 cm, the defoaming time was less than 1 second, and the amine solution did not foam. The simulated Claus tail gas was desulfurized using the same method as in Example 1. The purified gas contained 48.1 ppm H2S, 22.4 ppm CO2, and 14.4% CO2. The amine solution did not foam.

[0077] Comparative Example 3

[0078] The desulfurization solvent was prepared according to the method in Example 1, except that phosphazene was not added, and 5g of conventional desulfurization solvent sulfolane was added.

[0079] Simulated natural gas was desulfurized using the same method as in Example 1. The purified gas contained 5.7 ppm H2S and 1.0% CO2. The foam height was approximately 9.8 cm, and the defoaming time was approximately 8.5 s. Simulated Claus tail gas was also desulfurized using the same method as in Example 1. The purified gas contained 6.7 ppm H2S, 15.2 ppm CO2, and 14.0% CO2. The foam height was approximately 9.8 cm, and the defoaming time was approximately 8.5 s.

[0080] Comparative Example 4

[0081] The desulfurization solvent was prepared according to the method in Example 1, except that 10g of methyldiethanolamine was used instead of DTBP and phosphazene, and a total of 50g of methyldiethanolamine was added.

[0082] The simulated Claus tail gas was desulfurized using the same method as in Example 1. The purified gas contained 30.9 ppm H2S, 32.0 ppm COS, and 14.8% CO2. The foam height was approximately 1.2 cm, the defoaming time was less than 1 second, and the amine solution did not foam.

[0083] Comparative Example 5

[0084] The desulfurization solvent was prepared according to the method in Example 1, except that 2g of phosphazene and 43g of methyldiethanolamine were added, while the amounts of other components were the same as in Example 1.

[0085] The simulated natural gas was desulfurized using the same method as in Example 1. The purified gas contained 6.6 ppm H2S and 2.4% CO2. The foam height was approximately 1.0 cm, the defoaming time was approximately 1 second, and the amine solution did not foam. The simulated Claus tail gas was desulfurized using the same method as in Example 1. The purified gas contained 8.0 ppm H2S, 12.5 ppm CO2, and 14.4% CO2. The amine solution did not foam.

[0086] Comparative Example 6

[0087] The desulfurization solvent was prepared according to the method in Example 1, except that 0.5g of DTBP and 44.5g of methyldiethanolamine were added, while the amounts of other components were the same as in Example 1.

[0088] The simulated natural gas was desulfurized using the same method as in Example 1. The purified gas contained 5.9 ppm H2S and 1.8% CO2. The foam height was approximately 1.0 cm, the defoaming time was less than 1 second, and the amine solution did not foam. The simulated Claus tail gas was also desulfurized using the same method as in Example 1. The purified gas contained 2.8 ppm H2S, 3.1 ppm CO2, and 13.9% CO2. The amine solution did not foam.

[0089] As can be seen from the natural gas purification and desulfurization in Examples 1-9, the purified gas treated with the desulfurization solvent of this invention has extremely low H2S content, with an H2S removal rate close to 100%, and good CO2 selectivity, especially when DTBP is selected as the hindered amine, the CO2 selectivity is even better. This may be because the combination of hindered amine, alkanolamine, and phosphazene is used. Phosphazene, due to its strong alkalinity and special dendritic structure, works synergistically with the hindered amine, ensuring the purity and quality of the purified natural gas while maintaining good CO2 selectivity and a high H2S removal rate. This solvent also has excellent anti-foaming properties, ensuring stable operation of the device. Compared to Example 1, the desulfurization solvent used in Example 5 contains less hindered amine, with a mass ratio of hindered amine to alkanolamine less than 1:10, resulting in a slightly lower H2S removal rate in natural gas purification and desulfurization. Compared to Example 1, the desulfurization solvent used in Example 6 contains less phosphazene, with a mass ratio of phosphazene to alkanolamine less than 1:10, resulting in a slightly lower H2S removal rate in natural gas purification and desulfurization. Compared to Example 1, Example 8, due to the selection of a higher standard volume ratio and a relatively lower desulfurization solvent content, resulted in a decrease in desulfurization efficiency during natural gas purification and desulfurization. Compared to Example 1, Example 9, due to the selection of a lower pressure, also resulted in a decrease in desulfurization efficiency during natural gas purification and desulfurization.

[0090] As can be seen from the Claus tail gas purification and desulfurization in Examples 1-7 and 10-11, the purification gas treated with the desulfurization solvent of this invention exhibits a H2S removal rate greater than 95%, a COS removal rate greater than 85%, and good CO2 selectivity. This may be due to the use of a combination of hindered amines, alkanolamines, and phosphazenes. Phosphazenes, due to their strong alkalinity and unique dendritic structure, synergistically work with the hindered amines, ensuring the purity and quality of the purified Claus tail gas while achieving good CO2 selectivity, simultaneous removal of H2S and COS, and a high COS removal rate, even achieving complete COS removal. This solvent also possesses excellent anti-foaming properties, ensuring stable operation of the device. Compared to Example 1, the desulfurization solvent used in Example 5 contains less hindered amine, with a hindered amine to alkanolamine mass ratio of less than 1:10, resulting in a lower H2S and COS removal rate in the Claus tail gas purification and desulfurization. Compared to Example 1, Example 6 used a lower concentration of phosphazene in its desulfurization solvent, with a phosphazene to alkanolamine mass ratio of less than 1:10. This resulted in a decrease in the removal rates of H2S and COS in the Claus tail gas purification and desulfurization process. Compared to Example 1, Example 10, due to the selection of a higher standard volume ratio, had a relatively lower desulfurization solvent content, leading to a decrease in desulfurization efficiency in the Claus tail gas purification and desulfurization process. Example 11, due to the selection of a lower standard volume ratio, had a relatively higher desulfurization solvent content, resulting in the absorption of more CO2 gas and a decrease in selectivity in the Claus tail gas purification and desulfurization process.

[0091] A comparison of Example 1 and Comparative Example 1 shows that, without the addition of phosphazene, using an equal amount of DTBP to replace phosphazene results in a lower H2S removal rate in natural gas purification and desulfurization; and a lower removal rate of H2S and COS in Claus tail gas purification and desulfurization.

[0092] A comparison of Example 1 and Comparative Example 2 shows that, without the addition of hindered amines and by replacing DTBP with an equal amount of phosphazene, the removal rate of H2S decreases in natural gas purification and desulfurization; and the removal rates of H2S and COS decrease in Claus tail gas purification and desulfurization.

[0093] A comparison of Example 1 and Comparative Example 3 shows that, without the addition of phosphazene, and using an equal amount of conventional desulfurization solvent sulfolane instead of phosphazene, more CO2 gas is absorbed in natural gas purification desulfurization, resulting in poor selectivity and poor anti-foaming ability, while the amine solution is prone to foaming. In Claus tail gas purification desulfurization, the removal rates of H2S and COS are significantly reduced, indicating that traditional desulfurization solvents are not suitable for removing organic sulfur such as COS, and that they have poor CO2 selectivity, poor anti-foaming ability, and are prone to foaming.

[0094] A comparison of Example 1 and Comparative Example 4 shows that, without the addition of DTBP and phosphazene, and by using an equal amount of methyldiethanolamine to replace DTBP and phosphazene, the removal rates of H2S and COS are significantly reduced in Claus tail gas purification and desulfurization.

[0095] A comparison of Example 1 and Comparative Example 5 shows that insufficient phosphazene content resulted in a reduced H2S removal rate in natural gas purification and desulfurization; the removal rates of H2S and COS also decreased in Claus tail gas purification and desulfurization.

[0096] A comparison of Example 1 and Comparative Example 6 shows that the amount of hindered amine added was insufficient, resulting in a decrease in the removal rate of H2S in natural gas purification and desulfurization; the removal rates of H2S and COS were also reduced in Claus tail gas purification and desulfurization.

[0097] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A desulfurization solvent, characterized in that, The desulfurization solvent, in 100 wt% form, comprises: 1 wt%-20 wt% of hindered amine, 30 wt%-50 wt% of alkanolamine, 3 wt%-8 wt% of phosphazene, and the balance being water.

2. The desulfurization solvent according to claim 1, characterized in that, The desulfurization solvent, in 100 wt% form, comprises: 5 wt%-15 wt% of hindered amine, 35 wt%-45 wt% of alkanolamine, 5 wt%-8 wt% of phosphazene, and the balance being water; Preferably, it comprises: 10wt%-15wt% of hindered amine, 40wt%-45wt% of alkanolamine, 5wt%-8wt% of phosphazene and the balance being water.

3. The desulfurization solvent according to claim 1 or 2, characterized in that, The sterically hindered amine is selected from at least one of 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,5,7-triazidobicyclo[4.4.0]dec-5-ene, 1,3-bis(tert-butylamino)-2-propanol, 1,3-di(dimethylamino)-2-propanol, tert-butylaminoethoxyethanol, tert-butylaminoethanol, tert-butylaminodiethoxyethanol, 2-amino-2-methyl-1-propanol, N,N'-bis(2-hydroxyethyl)piperazine, N,N'-bis(2-hydroxypropyl)piperazine, and 1-(2-hydroxyethyl)-4-(2-hydroxypropyl)piperazine.

4. The desulfurization solvent according to claim 1 or 2, characterized in that, The hindered amine is selected from at least one of 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,3-bis(tert-butylamino)-2-propanol, tert-butylaminoethoxyethanol, tert-butylaminoethanol, 2-amino-2-methyl-1-propanol, and N,N'-bis(2-hydroxyethyl)piperazine; preferably 1,3-bis(tert-butylamino)-2-propanol.

5. The desulfurization solvent according to any one of claims 1-4, characterized in that, The alkanolamine is selected from at least one of methyldiethanolamine, monoethanolamine, diethanolamine, and diisopropanolamine.

6. A method for preparing the desulfurization solvent according to any one of claims 1-5, comprising the following steps: Bounded amine, alkanolamine, phosphazene and water are added to a mixer and stirred to obtain a desulfurization solvent; Preferably, the mixing conditions include: a stirring speed of 400-600 r / min and a temperature of 20-30℃.

7. The use of the desulfurization solvent according to any one of claims 1-5 or the desulfurization solvent prepared by the preparation method according to claim 6 for desulfurization in natural gas purification or Claus tail gas purification.

8. A desulfurization method for natural gas purification, characterized in that, Sulfur-containing natural gas is contacted with a desulfurization solvent in a desulfurization container to perform desulfurization; wherein the desulfurization solvent is selected from the desulfurization solvent described in any one of claims 1-5 or the desulfurization solvent prepared by the preparation method described in claim 6; Preferably, the contact is a countercurrent contact, the standard volume ratio of the sulfur-containing natural gas to the desulfurization solvent is (300-600):1; the pressure of the sulfur-containing natural gas is 3-8 MPa; and the sulfur-containing natural gas contains 2%-10% H2S and 3%-12% CO2.

9. The desulfurization method according to claim 8, characterized in that, The standard volume ratio of the sulfur-containing natural gas to the desulfurization solvent is (400-500):1; the pressure of the sulfur-containing natural gas is 4-6 MPa.

10. A desulfurization method for Claus tail gas purification, characterized in that, Sulfur-containing Claus tail gas is contacted with a desulfurization solvent in a desulfurization vessel for desulfurization; wherein the desulfurization solvent is selected from the desulfurization solvent described in any one of claims 1-5 or the desulfurization solvent prepared by the preparation method described in claim 6. Preferably, the contact is a countercurrent contact, and the standard volume ratio of the sulfur-containing Claus tail gas to the desulfurization solvent is (50-600):1, preferably (150-500):1; the sulfur-containing Claus tail gas is at atmospheric pressure; the sulfur-containing Claus tail gas contains 60-200 ppm H2S, 20-100 ppm COS, and 10%-30% CO2.

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