Absorption solvent for decarburization of natural gas as well as preparation method and application of absorption solvent

Abstract

The invention relates to the field of natural gas decarburization, and discloses an absorption solvent for natural gas decarburization as well as a preparation method and application thereof. Wherein the absorption solvent comprises a main agent, an activating agent and a defoaming agent, the main agent is selected from N-methyldiethanolamine, the activating agent is selected from one or more of diethanol amine, triethanolamine, methyl monoethanolamine, piperazine, hydroxyethyl piperazine, 2-piperidine ethanol and tert-butylamino diethanol amine, and the defoaming agent is selected from one or more of diethanol amine, triethanolamine, methyl monoethanolamine, piperazine, hydroxyethyl piperazine, 2-piperidine ethanol and tert-butylamino diethanol amine. The defoaming agent is a composite defoaming agent consisting of dimethyl silicone oil, hydrophobic silicon dioxide and dimethylformamide. The stability of the decarburization absorption solvent for natural gas decarburization is guaranteed, and a guarantee is provided for normal and stable operation of a decarburization system.

Description

Technical Field

[0001] The present invention relates to the field of natural gas decarbonization, and in particular to an absorption solvent for natural gas decarbonization and a preparation method and application thereof. Background Art

[0002] In recent years, with the gradual maturity of the natural gas industry, natural gas pretreatment and development and application have made great progress. The alkanolamine method has always been the mainstream method for decarbonizing the raw gas from natural gas, petroleum and its processing industry. Among them, the compound amine liquid formula with MDEA as the main body has formed a variety of optional amine desulfurization and decarbonization solutions, such as monoethanolamine, diethanolamine, triethanolamine, methyl monoethanolamine and methyl diethanolamine, which have the advantages of high stability, low regeneration energy consumption and low price. However, due to the disadvantage of MDEA itself that it is easy to foam, it affects the safe and stable operation of the absorption tower and regeneration tower and even the entire desulfurization and decarbonization system.

[0003] When the defoamer is used, due to its own water dispersibility, the defoamer molecules can be quickly distributed to the foam surface, forming a very thin surface film layer, and then penetrate and diffuse. The defoamer molecules adhere to the foam surface. Due to its own low tension, it will be pulled by the surrounding foam layer with greater surface tension, causing the foam liquid film stress imbalance, continuous thinning and eventually rupture. As the solution system flows, the defoamer will repeatedly attach and migrate on the existing foam layer, causing the foam system to continuously rupture and disintegrate, ultimately achieving the purpose of defoaming and breaking bubbles.

[0004] There are many kinds of commercial defoamers at home and abroad, mainly silicone, polysiloxane, vegetable oil, etc. Among them, silicone defoamers have good defoaming and suppression performance because polysiloxane has low surface tension and is incompatible with various substances. The present invention studies the foaming characteristics of natural gas amine liquid formula and conducts defoaming experiments to analyze the interaction between various factors under mixed impurities. Based on the above research, a reliable and stable defoamer suitable for natural gas decarbonization is proposed. Summary of the invention

[0005] The purpose of the present invention is to overcome the problem of easy foaming of absorption solvents used for natural gas decarbonization in the prior art, and to provide an absorption solvent used for natural gas decarbonization and a preparation method and application thereof.

[0006] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides an absorption solvent for natural gas decarbonization, wherein the absorption solvent comprises a main agent, an activator, a defoaming agent and water, wherein the main agent is selected from N-methyldiethanolamine, the activator is selected from one or more of diethanolamine, triethanolamine, methylmonoethanolamine, piperazine, hydroxyethylpiperazine, 2-piperidineethanol and tert-butylaminodiethanolamine, and the defoaming agent is a composite defoaming agent composed of dimethyl silicone oil, hydrophobic silica and dimethylformamide.

[0007] The second aspect of the present invention provides a method for preparing an absorption solvent for natural gas decarbonization, wherein the preparation method comprises: adding a main agent, an activator and a defoaming agent to a reactor in sequence, and stirring the obtained mixed liquid to prepare the absorption solvent.

[0008] The third aspect of the present invention provides an absorption solvent as described above and use of the absorption solvent obtained by the preparation method in natural gas decarbonization.

[0009] Through the above technical scheme, the absorption solvent for natural gas decarbonization provided by the present invention contains a specific composite defoaming agent, which achieves the defoaming principle by reducing the local surface tension of the foam, changing the stress balance, changing the liquid film properties, and causing the bubbles to burst. It has good stability and defoaming performance, and can inhibit the foam aggregation of the amine aqueous solution to a large extent. At the same time, it can reduce the addition of defoaming agent, ensure the stability of the decarbonization absorption solvent, and provide guarantee for the normal and stable operation of the decarbonization system. DETAILED DESCRIPTION

[0010] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the 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 as specifically disclosed in this article.

[0011] The first aspect of the present invention provides an absorption solvent for natural gas decarbonization, wherein the absorption solvent comprises a main agent, an activator, a defoaming agent and water, wherein the main agent is selected from N-methyldiethanolamine, the activator is selected from one or more of diethanolamine, triethanolamine, methylmonoethanolamine, piperazine, hydroxyethylpiperazine, 2-piperidineethanol and tert-butylaminodiethanolamine, and the defoaming agent is a composite defoaming agent composed of dimethyl silicone oil, hydrophobic silica and dimethylformamide.

[0012] In the present invention, the composite defoamer used in the absorption solvent is a combination of dimethyl silicone oil, hydrophobic silica and dimethylformamide, which is compounded with the main agent and the activator. The components interact with each other to reduce the local surface tension of the foam, change the stress balance, change the liquid film properties, and rupture the bubbles to achieve the defoaming principle. The invention has good stability and defoaming performance, can inhibit the foam aggregation of the amine aqueous solution to a large extent, and can reduce the addition of the defoamer to ensure the stability of the decarbonization absorption solvent.

[0013] In some specific embodiments of the present invention, based on the total amount of the absorption solvent, the content of the main agent is 25-45wt%, the content of the activator is 5-10wt%, the content of the defoamer is 0.01-0.2wt%, and the content of water is 44.8-70wt%.

[0014] In some specific embodiments of the present invention, preferably, the content of the main agent is 35-45wt%, the content of the activator is 5-8wt%, the content of the defoamer is 0.01-0.1wt%, and the content of water is 45-55wt%.

[0015] In some specific embodiments of the present invention, based on the total amount of the absorption solvent, the content of dimethyl silicone oil in the defoaming agent is 0.01-0.05wt%, the content of hydrophobic silica is 0.01-0.03wt%, and the content of dimethylformamide is 0.01-0.02wt%. The above solution content ratio can exert the effect of the defoaming agent itself to a greater extent and effectively reduce the foaming phenomenon of the solution.

[0016] In some specific embodiments of the present invention, the mass ratio of the dimethyl silicone oil, hydrophobic silica and dimethylformamide is 2-4:1-2:1. Through the above-mentioned specific ratio of the three components of the composite defoamer, the foam aggregation of the amine aqueous solution can be suppressed to a large extent, and the addition of the defoamer can be reduced to ensure the stability of the decarbonization absorption solvent.

[0017] In some specific embodiments of the present invention, the absorption solvent reduces the local surface tension of the foam due to the combined action of the composite defoamer while ensuring the decarbonization capacity, thereby largely inhibiting the foam aggregation of the amine solution, greatly reducing the defoaming time, and improving the stability of the solution. At the same time, silicon dioxide has strong hydrophobicity and has the effect of destroying the surfactant interface, thereby effectively inhibiting the foaming of the absorption solvent.

[0018] In the present invention, the composite defoamer used in the absorption solvent is a combination of dimethyl silicone oil, hydrophobic silica and dimethylformamide, which is compounded with the main agent and the activator. The components interact with each other and can adapt to the conventional mixed impurities in the natural gas system, such as Fe 3+ Mg 2+ , Ca 2+ , formic acid, oxalic acid, acetic acid, activated carbon, etc. The absorption solvent for natural gas decarbonization of the present invention has the characteristics of good adaptability, less addition and good defoaming performance.

[0019] The second aspect of the present invention provides a method for preparing an absorption solvent for natural gas decarbonization, wherein the preparation method comprises: adding a main agent, an activator and a defoaming agent to a reactor in sequence, and stirring the obtained mixed liquid to prepare the absorption solvent.

[0020] In some specific embodiments of the present invention, based on the total amount of the absorption solvent, the content of the main agent is 25-45wt%, the content of the activator is 5-10wt%, and the content of the defoaming agent is 0.01-0.2wt%.

[0021] In some embodiments of the present invention, preferably, the content of the main agent is 35-45wt%, the content of the activator is 5-8wt%, and the content of the defoamer is 0.01-0.1wt%.

[0022] The third aspect of the present invention provides an absorption solvent as described above and use of the absorption solvent obtained by the preparation method in natural gas decarbonization.

[0023] In some embodiments of the present invention, the absorption solvent is used at a temperature of 30-140°C, preferably 40-110°C.

[0024] In some embodiments of the present invention, the use pressure of the absorption solvent is 0.5-10 MPa, preferably 1.5-8 MPa.

[0025] According to a particularly preferred embodiment of the present invention, there is provided an absorption solvent for natural gas decarbonization, wherein the absorption solvent comprises a main agent, an activator and a defoamer, wherein the main agent is selected from N-methyldiethanolamine, the activator is selected from one or more of diethanolamine, triethanolamine, methyl monoethanolamine, piperazine, hydroxyethylpiperazine, 2-piperidineethanol and tert-butylaminodiethanolamine, and the defoamer is a composite defoamer composed of dimethyl silicone oil, hydrophobic silica and dimethylformamide;

[0026] Based on the total amount of the absorption solvent, the content of the main agent is 35-45wt%, the content of the activator is 5-8wt%, and the content of the defoaming agent is 0.01-0.1wt%.

[0027] Based on the total amount of the absorption solvent, in the defoaming agent, the content of dimethyl silicone oil is 0.01-0.05wt%, the content of hydrophobic silica is 0.01-0.03wt%, and the content of dimethylformamide is 0.01-0.02wt%; the mass ratio of the dimethyl silicone oil, hydrophobic silica and dimethylformamide is 2-4:1-2:1.

[0028] The present invention will be described in detail below through examples.

[0029] In the following examples and comparative examples, if no specific conditions are specified, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, if no manufacturer is specified, are all conventional products that can be obtained through commercial channels.

[0030] Example 1

[0031] The main agent MDEA (40wt%), the activator DEA (5wt%) and the defoaming agent (dimethyl silicone oil (0.04wt%), hydrophobic silica (0.02wt%), dimethylformamide (0.01wt%)) were added to the reactor in sequence, and the mixed liquid was stirred to obtain the absorption solvent 1.

[0032] Examples 2-8 and Comparative Examples 1-5 were prepared according to the method of Example 1, and the compositions of the absorption solvents are shown in Table 1.

[0033] Table 1

[0034]

[0035]

[0036]

[0037] Test Case

[0038] Take 20mL of absorption solvent and put it into a foam height test tube, and put it into a constant temperature water bath at (40±1)℃ for 10 minutes. After the nitrogen passes through the rotor flowmeter, it passes through the bottom inlet of the foam height test tube. The flow rate reaches 450mL / min and starts timing after it stabilizes. Ventilate for 5 minutes, stop ventilation, record the foam height (the difference between the final foam height of the liquid surface and the initial solution height) and defoaming time (time after stopping the gas, stop when the foam just bursts and clear liquid is seen). The bubble surface height describes the foaming trend of the solution, the defoaming time describes the defoaming performance of the defoaming agent, and the amount of the defoaming agent determines the usage time.

[0039] The results of bubble height and defoaming time are shown in Table 1.

[0040] Comparative Examples and Example Results:

[0041] Compared with comparative documents 1-3, Examples 1-8 support the present invention by limiting the component range, interaction and effect factors of the main agent, activator and defoamer.

[0042] Compared with Comparative Examples 4 and 5, Examples 1 and 2 use a composite defoaming agent that is a combination of dimethyl silicone oil, hydrophobic silica and dimethylformamide. The components interact with each other to form an absorption solvent with better defoaming performance. The defoaming principle is achieved by reducing the local surface tension of the foam, changing the stress balance, changing the liquid film properties, and rupturing the bubbles. The defoaming has good stability and defoaming performance, and the foam aggregation of the amine aqueous solution can be suppressed to a large extent. At the same time, the addition of defoaming agent can be reduced to ensure the stability of the decarbonization absorption solvent.

[0043] In Example 1, compared with Examples 9 and 10, when the mass ratio of the dimethyl silicone oil, hydrophobic silica and dimethylformamide is 2-4:1-2:1, the defoaming performance of the absorption solvent is better. When it exceeds the range of the above-mentioned specific ratio of the present invention, the defoaming performance is relatively poor.

[0044] Compared with comparative documents 1-3 and embodiments 3 and 4, embodiments 7 and 8 show that the absorption solvent for natural gas decarbonization has the characteristics of good adaptability, less addition and good defoaming performance by adding conventional mixed impurities of the natural gas system.

[0045] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. An absorption solvent for natural gas decarbonization, characterized in that: The absorption solvent comprises a main agent, an activator, a defoamer and water, wherein the main agent is selected from N-methyldiethanolamine, the activator is selected from one or more of diethanolamine, triethanolamine, methylmonoethanolamine, piperazine, hydroxyethylpiperazine, 2-piperidineethanol and tert-butylaminodiethanolamine, and the defoamer is a composite defoamer composed of dimethyl silicone oil, hydrophobic silica and dimethylformamide.

2. The absorption solvent according to claim 1, characterized in that Based on the total amount of the absorption solvent, the content of the main agent is 25-45wt%, the content of the activator is 5-10wt%, the content of the defoamer is 0.01-0.2wt%, and the content of water is 44.8-70wt%.

3. The absorption solvent according to claim 1 or 2, characterized in that Based on the total amount of the absorption solvent, the content of the main agent is 35-45wt%, the content of the activator is 5-8wt%, the content of the defoamer is 0.01-0.1wt%, and the content of water is 45-55wt%.

4. The absorption solvent according to any one of claims 1 to 3, characterized in that Based on the total amount of the absorption solvent, in the defoaming agent, the content of dimethyl silicone oil is 0.01-0.05wt%, the content of hydrophobic silica is 0.01-0.03wt%, and the content of dimethylformamide is 0.01-0.02wt%; Preferably, the mass ratio of the dimethyl silicone oil, hydrophobic silica and dimethylformamide is 2-4:1-2:

1.

5. A method for preparing an absorption solvent for natural gas decarbonization, characterized in that: The preparation method comprises: adding a main agent, an activator and a defoamer into a reaction kettle in sequence, and stirring the obtained mixed liquid to obtain the absorption solvent.

6. The preparation method according to claim 5, characterized in that: Based on the total amount of the absorption solvent, the content of the main agent is 25-45wt%, the content of the activator is 5-10wt%, and the content of the defoamer is 0.01-0.2wt%.

7. The preparation method according to claim 6, characterized in that: The content of the main agent is 35-45wt%, the content of the activator is 5-8wt%, and the content of the defoamer is 0.01-0.1wt%.

8. Use of the absorption solvent according to any one of claims 1 to 4 and the absorption solvent obtained by the preparation method according to any one of claims 5 to 7 in natural gas decarbonization.

9. The use according to claim 8, characterized in that: The use temperature of the absorption solvent is 30-140°C, preferably 40-110°C.

10. The use according to claim 8 or 9, characterized in that: The use pressure of the absorption solvent is 0.5-10 MPa, preferably 1.5-8 MPa.

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