Desulfurizing agent and its application and natural gas desulfurization method

Abstract

The present invention relates to the technical field of natural gas purification and treatment, and specifically to a desulfurizer, its application, and a natural gas desulfurization method. The desulfurization solvent contains a main agent, an auxiliary agent, and an additive; the main agent is a mixture of polyamide-amine and 2-tert-butylaminoethanol; the auxiliary agent is selected from N,N-diethylethanolamine and / or N-methyldiethanolamine; the additive is selected from sodium sulfite and / or potassium sorbate; based on the total mass of the desulfurizer, the main agent content is 45% to 70%; the auxiliary agent content is 30% to 55%; the additive content is 0.01 to 0.1%; in the main agent, the mass ratio of polyamide-amine to 2-tert-butylaminoethanol is not less than 0.5. Under the premise of basically not changing the existing amine-based natural gas desulfurization device, the sulfur-containing substances are removed in one step to make its H2S content less than 6 mg / m 3 , total sulfur <20mg / m 3 At the same time, the CO2 content is maintained above 1.8 mol%, making it a commercial natural gas that meets quality indicators.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas purification and treatment, in particular to a desulfurizing agent and application thereof, and a natural gas desulfurization method. Background Art

[0002] The current Natural Gas (GB17820-2018) standard requires that the H2S content of natural gas entering long-distance pipelines be less than 6 mg / m 3 , total sulfur <20mg / m 3 To meet this standard, existing domestic desulfurization equipment has incurred significant costs, either through technological upgrades, reducing loads to achieve quality targets, or increasing energy consumption to meet targets. Therefore, there is an urgent need to improve the performance of desulfurization solvents to fully utilize the load of existing equipment.

[0003] In natural gas purification processes, the alcoholamine method is widely used to remove CO2 and H2S from sour natural gas. Currently, the main alcoholamine solvents used are N-methyldiethanolamine (MDEA) and various MDEA formulations. Overall, MDEA and its formulations have limited ability to remove COS, CS2, and RSH from natural gas, making it difficult to ensure that the sulfur content of the product gas meets the long-distance pipeline requirements of GB17820-2018. Even if the technical indicators meet the sulfide requirements, the CO2 content is reduced to below 0.5 mol%, far below the 3 mol% or 4 mol% in commercial gas specified in GB17820-2018, reducing the economic benefits of the enterprise. Although COS and CS2 can be industrially removed by converting them into H2S and CO2 through hydrolysis, such as EP1791622A1, which mentions the use of solid hydrolyzing agents to convert COS in a gas stream into H2S and CO2, CN101175547B proposes the use of iron oxides to achieve fine desulfurization of COS in a gas stream at certain optimal temperatures, pressures, and space velocities. Neither hydrolysis nor iron oxide fine desulfurization can effectively reduce RSH content. Molecular sieves, such as CA2614169A1, can be used industrially to remove RSH. However, molecular sieves also adsorb H2S, COS, and CS2, requiring a large amount of purified commercial gas to be used as regeneration gas to regenerate the molecular sieve.

[0004] Therefore, in order to meet the current strict natural gas quality standards, there is an urgent need to upgrade the existing natural gas desulfurization solvent, which can not only remove sulfides but also make the CO2 content as high as possible while meeting the indicators. Summary of the Invention

[0005] The purpose of the present invention is to provide a desulfurizer, which can be used for desulfurization of sulfur-containing gases such as natural gas to improve the absorption selectivity of hydrogen sulfide and organic sulfur and reduce the absorption selectivity of carbon dioxide; reduce the hydrogen sulfide content and total sulfur content in natural gas and increase the carbon dioxide content.

[0006] In order to achieve the above-mentioned object, the first aspect of the present invention provides a desulfurization agent, which contains a main agent, an auxiliary agent and an additive;

[0007] The main agent is a mixture of polyamide-amine and 2-tert-butylaminoethanol;

[0008] The auxiliary agent is selected from N, N-diethylethanolamine and / or N-methyldiethanolamine;

[0009] The additive is selected from sodium sulfite and / or potassium sorbate; based on the total mass of the desulfurizer, the content of the main agent is 45% to 70%; the content of the auxiliary agent is 30% to 55%; the content of the additive is 0.01 to 0.1%; in the main agent, the mass ratio of polyamide-amine to 2-tert-butylaminoethanol is 2:1-1:2.

[0010] A second aspect of the present invention provides a use of the desulfurizing agent of the present invention in desulfurizing sulfur-containing gas.

[0011] A third aspect of the present invention provides a natural gas desulfurization method, the method comprising:

[0012] The sulfur-containing natural gas is introduced into a desulfurization solvent for desulfurization, wherein the desulfurization solvent contains the desulfurizer of the present invention.

[0013] Through the above technical solution, the desulfurizer described in the present invention is used to reduce the sulfide content and retain more CO2 without basically changing the process of the existing sulfur-containing gas (such as sulfur-containing natural gas) purification device, thereby improving the economic benefits of the desulfurization device while maintaining or increasing the processing load.

[0014] Under the premise of not changing the existing amine-based natural gas desulfurization equipment, H2S, COS, CS2 and RSH in natural gas are removed in one step to make the H2S content lower than 6mg / m 3 , total sulfur <20mg / m 3 At the same time, the CO2 content is maintained above 1.8 mol%, making it a commercial natural gas that meets quality indicators. DETAILED DESCRIPTION

[0015] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0016] The first aspect of the present invention provides a desulfurization agent, which contains a main agent, an auxiliary agent and an additive;

[0017] The main agent is a mixture of polyamide-amine and 2-tert-butylaminoethanol;

[0018] The auxiliary agent is selected from N, N-diethylethanolamine and / or N-methyldiethanolamine;

[0019] The additive is selected from sodium sulfite and / or potassium sorbate; based on the total mass of the desulfurizer, the content of the main agent is 45% to 70%; the content of the auxiliary agent is 30% to 55%; the content of the additive is 0.01 to 0.1%; in the main agent, the mass ratio of polyamide-amine to 2-tert-butylaminoethanol is 2:1-1:2.

[0020] The desulfurizer can be used for natural gas desulfurization to improve the absorption selectivity of hydrogen sulfide and organic sulfur and reduce the absorption selectivity of carbon dioxide; reduce the hydrogen sulfide content and total sulfur content in natural gas and increase the carbon dioxide content.

[0021] In the present invention, the mass ratio of polyamide-amine to 2-tert-butylaminoethanol in the main agent can be selected in a wide range. According to a preferred embodiment of the present invention, the mass ratio of polyamide-amine to 2-tert-butylaminoethanol is 1:1 to 1:2.0.

[0022] In the present invention, the chemical formula of 2-tert-butylaminoethanol is shown in formula (I);

[0023]

[0024] In the present invention, there is no particular limitation on the type of the polyamide-amine. According to a preferred embodiment of the present invention, the initiating core of the polyamide-amine is ethylenediamine and / or ammonia, and the terminal group is an amino group and / or a hydroxyl group; preferably, the generation number of the polyamide-amine is 1-5 generations, preferably 2-4 generations.

[0025] Those skilled in the art know that in a polyamide-amine molecule with an amino group as the terminal group, a molecule with an ester group as the terminal group can be formed by reacting the amino group with methyl acrylate, and then an amidation reagent is added, and the ester group reacts with the amidation reagent to form a polyamide-amine molecule with an amino group as the terminal group.

[0026] Those skilled in the art are aware that the conventional preparation method for polyamidoamines generally follows the following steps: First, an initiator (e.g., ethylenediamine) reacts with methyl acrylate via a Michael addition reaction to form a tetrabasic ester, known as the 0.5 generation. Second, the tetrabasic ester undergoes an aminolysis reaction with an amidating agent to form a tetrabasic amide, known as the 1st generation polyamidoamine. These first and second steps are repeated repeatedly to produce polyamidoamines of higher generations.

[0027] In the polyamide-amine, the source of the branched chains is methyl acrylate.

[0028] According to a preferred embodiment of the present invention, the auxiliary agent is preferably used alone when certain mass transfer devices that rely on centrifugal force are used.

[0029] A second aspect of the present invention provides a use of the desulfurizing agent of the present invention in desulfurizing sulfur-containing gas.

[0030] According to a preferred embodiment of the present invention, the sulfur-containing gas is selected from sulfur-containing natural gas.

[0031] A third aspect of the present invention provides a natural gas desulfurization method, the method comprising:

[0032] The sulfur-containing natural gas is introduced into a desulfurization solvent for desulfurization, wherein the desulfurization solvent contains the desulfurizer of the present invention.

[0033] According to a preferred embodiment of the present invention, the desulfurization solvent further contains water; preferably, the mass ratio of the desulfurization agent to water is 35-50:50-65.

[0034] According to a preferred embodiment of the present invention, the sour natural gas contains, by volume fraction, 0-20% H2S, 3-30% CO2, and 60-97% alkanes;

[0035] According to a preferred embodiment of the present invention, the sour natural gas further contains COS, CS2, and methyl mercaptan, and COS+CS2 is less than 200 mg / m 3 , methyl mercaptan as sulfur <100mg / m 3 .

[0036] According to a preferred embodiment of the present invention, the content of hydrocarbons above C5 in the sulfur-containing natural gas is less than 5%.

[0037] In the present invention, there is no particular limitation on the desulfurization conditions. Conventional natural gas desulfurization conditions in the art can be used in the present invention. Preferably, the desulfurization conditions include: raw natural gas temperature of 30-45°C, lean liquid temperature of 35-45°C, top pressure of the regeneration tower of 60-90 kPaG, and temperature of the regeneration tower bottom of 115-125°C.

[0038] The present invention has no special requirements for the mass transfer device for natural gas desulfurization and desulfurization solvent regeneration. According to a preferred embodiment of the present invention, the mass transfer device for natural gas absorption and desulfurization solvent regeneration is a tower device or a high-gravity rotating bed.

[0039] Unless otherwise specified, the test conditions for the Examples and Comparative Examples are as follows:

[0040] The pressure of the natural gas used in the test is 4.0 MPa, and the volume fraction of the main components is H2S 5.0%, CO2 7.0%, COS+CS2 calculated as sulfur 97 mg / m 3 , methyl mercaptan as sulfur 45mg / m 3 The raw natural gas enters the amine desulfurization and decarbonization unit at 35-40℃, and the lean liquid enters the absorption tower at 38-42℃. The pressure at the top of the regeneration tower is 70kPaG, and the temperature at the bottom of the tower is 115-120℃.

[0041] The desulfurization solvent consists of a desulfurizer and water, wherein the water content is 55 wt%.

[0042] Example 1

[0043] The desulfurizer consists of a third-generation polyamide-amine (PAA) with hydroxyl groups at the end and 2-tert-butylaminoethanol (TBA) in a 1:1 ratio, with the PAA and TBA at 50% by mass. The auxiliary agent is N,N-diethylethanolamine at 49.95% by mass, and the additive is sodium sulfite at 0.05% by mass. The test results are shown in Table 1.

[0044] Example 2

[0045] The desulfurizer consists of a third-generation polyamide-amine (PAA) with hydroxyl groups at the end and 2-tert-butylaminoethanol (TBA) in a 1:1 ratio, with the PAA and TBA accounting for 60% by mass. The auxiliary agent is N,N-diethylethanolamine (39.95% by mass), and the additive is sodium sulfite (0.05% by mass). The test results are shown in Table 1.

[0046] Example 3

[0047] The desulfurizer consists of a third-generation polyamide-amine (PAA) with hydroxyl groups at the end and 2-tert-butylaminoethanol (TBA):2-tert-butylaminoethanol (1:1) as the main agent, with a mass fraction of 70%. The auxiliary agent is N,N-diethylethanolamine (29.95%), and the additive is sodium sulfite (0.05%). The test results are shown in Table 1.

[0048] Example 4

[0049] The desulfurizer consists of a third-generation polyamide-amine (PAA) with hydroxyl groups at the end and 2-tert-butylaminoethanol (2-tert-butylaminoethanol) in a ratio of 1:1.5. The main agent accounts for 60% by mass. The auxiliary agent is N,N-diethylethanolamine (39.95% by mass). The additive is sodium sulfite (0.05% by mass). The test results are shown in Table 1.

[0050] Example 5

[0051] The desulfurizer consists of a third-generation polyamide-amine (PAA) with hydroxyl groups at the end and 2-tert-butylaminoethanol (TBA) in a ratio of 1:2, with the PAA and 2-tert-butylaminoethanol at a mass fraction of 60%. The auxiliary agent is N,N-diethylethanolamine at a mass fraction of 39.95%. The additive is sodium sulfite at a mass fraction of 0.05%. The test results are shown in Table 1.

[0052] Example 6

[0053] The desulfurizer consists of a third-generation polyamide-amine (PAA) with hydroxyl groups at the end and 2-tert-butylaminoethanol (TBA) in a 1:1 ratio, with the PAA and TBA accounting for 60% by mass. The auxiliary agent is N-methyldiethanolamine (39.95% by mass), and the additive is potassium sorbate (0.05% by mass). The test results are shown in Table 1.

[0054] Example 7

[0055] The desulfurizer consists of a third-generation polyamide-amine (PAA) with hydroxyl groups at the end and 2-tert-butylaminoethanol (TBA) in a 1:1 ratio. The main agent accounts for 60% by weight, while the auxiliary agent is a 1:1 mixture of N,N-diethylethanolamine and N-methyldiethanolamine (39.95% by weight). The additive is sodium sulfite (0.05% by weight). The test results are shown in Table 1.

[0056] Example 8

[0057] The desulfurizer consists of a third-generation polyamide-amine (PAA) with amino end groups and 2-tert-butylaminoethanol (TBA) in a 1:1 ratio. The main agent accounts for 60% by weight, while the auxiliary agent is a mixture of N,N-diethylethanolamine and N-methyldiethanolamine (N-methyldiethanolamine) in a 1:3 ratio, accounting for 39.95% by weight. The additive is sodium sulfite, accounting for 0.05% by weight. The test results are shown in Table 1.

[0058] Example 9

[0059] The desulfurizer consists of a first-generation polyamide-amine (PAA) with hydroxyl groups at the end and 2-tert-butylaminoethanol (TBA) in a 1:1 ratio. The PAA content is 60% by weight. The auxiliary agent is N,N-diethylethanolamine (39.95% by weight). The additive is sodium sulfite (0.05% by weight). The test results are shown in Table 1.

[0060] Example 10

[0061] The desulfurizer consists of a second-generation polyamide-amine (PAA) with hydroxyl groups at the end and 2-tert-butylaminoethanol (TBA) in a 1:1 ratio, with the PAA and TBA accounting for 60% by mass. The auxiliary agent is N,N-diethylethanolamine (39.95% by mass), and the additive is sodium sulfite (0.05% by mass). The test results are shown in Table 1.

[0062] Example 11

[0063] The desulfurizer consists of a 4th-generation polyamide-amine (PAA) with hydroxyl groups at the end and 2-tert-butylaminoethanol (TBA) in a 1:1 ratio. The PAA content is 60% by weight. The auxiliary agent is N,N-diethylethanolamine (39.95% by weight). The additive is sodium sulfite (0.05% by weight). The test results are shown in Table 1.

[0064] Example 12

[0065] The desulfurizer consists of a fifth-generation polyamide-amine (PAA) with hydroxyl groups at the end and 2-tert-butylaminoethanol (2-tert-butylaminoethanol) in a 1:1 ratio. The main agent accounts for 60% by mass. The auxiliary agent is N,N-diethylethanolamine (39.95% by mass). The additive is sodium sulfite (0.05% by mass). The test results are shown in Table 1.

[0066] Comparative Example 1

[0067] The desulfurizer formulation consists of a third-generation polyamidoamine (PAA) with hydroxyl groups at the end and 2-tert-butylaminoethanol (TBA), accounting for 40% by weight in a 1:1 ratio. The auxiliary agent is N,N-diethylethanolamine (NEA), accounting for 59.95%. Sodium sulfite is also added as an additive at 0.05%. The test results are shown in Table 1.

[0068] Comparative Example 2

[0069] The desulfurizer formulation consists of a third-generation polyamidoamine (PAA) with hydroxyl groups at the end and 2-tert-butylaminoethanol (TBA), accounting for 80% by weight. The PAA:TBA ratio is 1:1. The auxiliary agent is N,N-diethylethanolamine (NEA), accounting for 19.95%. Sodium sulfite is also added as an additive at 0.05%. The test results are shown in Table 1.

[0070] Comparative Example 3

[0071] The desulfurizer formulation consists of a third-generation polyamidoamine (PAA) with hydroxyl groups at the end and 2-tert-butylaminoethanol (TBA), with the PAA and TBA accounting for 60% by weight in a ratio of 3:1. The auxiliary agent is N,N-diethylethanolamine (NEA), accounting for 39.95%. Sodium sulfite is also added at 0.05%. The test results are shown in Table 1.

[0072] Comparative Example 4

[0073] The desulfurizer formulation consists of a third-generation polyamidoamine (PAA) with hydroxyl groups at the end and 2-tert-butylaminoethanol (TBA), accounting for 60% by weight (PAA:2-TBA in a 1:1 ratio). The auxiliary agent is N,N-diethylethanolamine (NDE), accounting for 39.8%. Potassium sorbate is also present as an additive at 0.20%. The test results are shown in Table 1.

[0074] Table 1

[0075] serial number <![CDATA[H2S(mg / m 3 )]]> <![CDATA[Total sulfur (mg / m 3 )]]> <![CDATA[CO2(mol%)]]> Example 1 3.1 13.6 2.2 Example 2 2.8 13.3 2.1 Example 3 2.6 13.0 2.0 Example 4 2.7 13.5 2.2 Example 5 3.0 14.2 2.2 Example 6 2.7 13.4 2.2 Example 7 2.8 13.5 2.2 Example 8 2.9 14.0 2.3 Example 9 1.9 12.3 1.8 Example 10 2.4 12.7 2.1 Example 11 2.5 12.9 2.3 Example 12 2.8 13.3 2.3 Comparative Example 1 4.7 24.5 2.3 Comparative Example 2 1.9 10.3 1.4 Comparative Example 3 1.2 9.9 0.9 Comparative Example 4 3.4 20.4 2.3

[0076] It can be seen from the above examples that the desulfurizer and the method of use of the present invention can increase the CO2 content in the purified gas while ensuring the desulfurization effect, which makes it simple and effective to modify the existing desulfurization device to improve the quality requirements of the product gas.

[0077] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A desulfurizing agent, characterized in that: The desulfurizer contains a main agent, auxiliary agent and additives; The main agent is a mixture of polyamide-amine and 2-tert-butylaminoethanol; The auxiliary agent is selected from N, N-diethylethanolamine and / or N-methyldiethanolamine; The additive is selected from sodium sulfite and / or potassium sorbate; Based on the total mass of the desulfurizer, the content of the main agent is 45%~70%; the content of the auxiliary agent is 30%~55%; the content of the additive is 0.01~0.1%, and the sum of the contents of each component is 100%; In the main agent, the mass ratio of polyamide-amine to 2-tert-butylaminoethanol is 2:1~1:

2.

2. The desulfurizing agent according to claim 1, wherein In the main agent, the mass ratio of polyamide-amine to 2-tert-butylaminoethanol is 1:1~1:

2.

3. The desulfurizing agent according to claim 1, wherein In the main agent, the initiating core of the polyamide-amine is ethylenediamine and / or ammonia, and the terminal group is an amino group and / or a hydroxyl group.

4. The desulfurizing agent according to any one of claims 1 to 3, wherein The molecular generation number of the polyamidoamine is 1 to 5.

5. The desulfurizing agent according to claim 4, wherein The molecular generation number of the polyamidoamine is 2-4.

6. The desulfurizing agent according to claim 4, wherein In the polyamide-amine, the source of the branched chains is methyl acrylate.

7. Use of the desulfurizing agent according to any one of claims 1 to 6 in the desulfurization of sulfur-containing gas; the sulfur-containing gas is selected from sulfur-containing natural gas.

8. A natural gas desulfurization method, characterized in that: The method comprises: introducing sulfur-containing natural gas into a desulfurization solvent for desulfurization, wherein the desulfurization solvent contains the desulfurizer according to any one of claims 1 to 6.

9. The desulfurization method according to claim 8, wherein: The desulfurization solvent also contains water.

10. The desulfurization method according to claim 9, wherein: The mass ratio of desulfurizer to water is 35-50:50-65.

11. The desulfurization method according to claim 8, wherein: Calculated by volume fraction, the sour natural gas contains 5-20% H2S, 3-30% CO2, and 60-97% alkanes, and the sum of the contents of each component is 100%.

12. The desulfurization method according to claim 11, wherein: The sour natural gas also contains COS, CS2, and methyl mercaptan, and COS+CS2 is less than 200 mg / m 3 , methyl mercaptan as sulfur <100mg / m 3 .

13. The desulfurization method according to claim 8 or 9, wherein: The desulfurization conditions include: the temperature of the sour natural gas is 30~45℃, the temperature of the lean liquid is 35~45℃, the top pressure of the regeneration tower is 60~90kPaG, and the temperature of the bottom of the regeneration tower is 115~125℃.

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