Absorbent and desulfurization method using the same

Abstract

The application provides an absorbent and a desulfurization method using the same. The absorbent comprises an alcohol amine compound, an ionic liquid and a polyhydric alcohol, can realize efficient absorption of hydrogen sulfide, mercaptan, sulfide, carbonyl sulfur and thiophene and other sulfur-containing compounds in oilfield associated gas, and at the same time, will not absorb heavy hydrocarbon components in the oilfield associated gas, avoiding the problem of liquid blocking and tower flushing caused by the foaming of the absorbent. The desulfurization method realizes efficient use and regeneration of the absorbent by setting the treatment conditions in the desulfurization tower and the regeneration tower.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas purification technology, and particularly relates to an absorbent and a desulfurization method using the same. Background Technology

[0002] Many oilfields in my country generate large amounts of associated gas during crude oil production. This associated gas often contains high levels of heavy hydrocarbons, primarily including methane, ethane, propane, butane, and hydrocarbons with more than five carbon atoms. In many cases, the content of C3 or higher components in associated gas exceeds 15%. Associated gas from sulfur-containing blocks typically contains significant amounts of sulfur-containing components, mainly hydrogen sulfide, carbonyl sulfide, thiols, thioethers, and thiophene compounds. In some blocks, the hydrogen sulfide content in associated gas exceeds 10%. This high-sulfur, high-heavy-hydrocarbon associated gas requires desulfurization and light hydrocarbon separation processes to produce qualified natural gas, liquefied petroleum gas (LPG), and light hydrocarbon products from the oilfield. For example, GB 17820-2018 stipulates that the hydrogen sulfide content in Class II natural gas for civilian use in my country should be less than 20 mg / Nm³. 3 Total sulfur content less than 200 mg / Nm 3 .

[0003] Alkanolamines are frequently used as desulfurizing agents, but using amines alone can only remove most of the hydrogen sulfide from natural gas, and their effect on removing carbonyl sulfide and organic sulfur compounds such as thiophene is poor. In traditional processing, hydrolysis is required to remove carbonyl sulfide and other organic sulfur compounds.

[0004] Traditional desulfurization absorbents are widely used in the desulfurization processes of dry gas and natural gas in refineries and operate stably. However, when directly applied to the desulfurization process of associated gas from oil fields with high sulfur and heavy hydrocarbon content, such desulfurization systems often struggle to operate stably and achieve poor desulfurization results. The main reason for this is that associated gas from oil fields contains a large amount of heavy hydrocarbons. The greater the amount of these heavy hydrocarbon molecules, the higher their solubility in the amine solution. The presence of heavy hydrocarbons leads to a severe tendency for the amine solution to foam, which can easily cause liquid clogging and tower flushing problems in the desulfurization system due to amine solution foaming. This threatens the long-term stable operation of the entire system and reduces desulfurization efficiency, making it difficult to meet the sulfur content standards in the purified gas. These problems have become technical challenges for the efficient purification of high-sulfur and high-heavy hydrocarbon associated gas. Summary of the Invention

[0005] One aspect of the present invention provides an absorbent comprising an alkanolamine compound, an ionic liquid, and a polyol.

[0006] In one specific embodiment, the anion of the ionic liquid is Lewis basic; and / or

[0007] The polyol is a diol and / or a triol;

[0008] Preferably, the ionic liquid is a dicyandiamide salt ionic liquid;

[0009] Preferably, the polyol is at least one of C2 to C4 diols.

[0010] In one specific embodiment, the absorbent comprises, by weight, 10% to 60% of an alkanolamine compound, 20% to 80% of an ionic liquid, and 10% to 70% of a polyol.

[0011] In one specific embodiment, the alkanolamine compound is at least one selected from monoethanolamine, diethanolamine, methylmonoethanolamine, and N-methyldiethanolamine.

[0012] In one specific embodiment, the ionic liquid is 1-methyl-3-ethylimidazolium dicyanamide salt and / or N-methyl-N-ethylpyrrole dicyanamide salt.

[0013] In one specific embodiment, the polyol is at least one selected from ethylene glycol, 1,2-propanediol, 1,3-propanediol, and 1,4-butanediol.

[0014] The second invention provides a desulfurization method, which includes the following steps:

[0015] 1) The associated gas and absorbent are brought into countercurrent contact in the desulfurization tower, and the purified associated gas is obtained at the top of the tower, while the absorbent is obtained at the bottom of the tower.

[0016] 2) The absorbent is discharged into a regeneration tower to obtain a regenerated absorbent;

[0017] 3) The regenerated absorbent is returned to the desulfurization tower for recycling;

[0018] The absorbent is the absorbent described in one of the present invention.

[0019] In one specific embodiment, the feed volume ratio of the associated gas and the absorbent is (100 to 500):1; and / or

[0020] The total sulfur content in the regenerated absorbent is less than 2 g / L.

[0021] In one specific embodiment, in the desulfurization tower, the feed temperature of the associated gas and the feed temperature of the absorbent are independently 30 to 50°C, and the pressure is 0.5 to 5.0 MPa; and / or

[0022] In the regeneration tower, the top temperature is 100 to 110°C, and the bottom temperature is 120 to 220°C; and / or

[0023] The desulfurization tower and regeneration tower are independently plate towers and / or packed towers; and / or

[0024] The number of tray layers in the desulfurization tower and the number of tray layers in the regeneration tower are independently 25 to 40;

[0025] Preferably, the number of tray layers in the desulfurization tower and the number of tray layers in the regeneration tower are independently 25 to 35.

[0026] The application of the absorbent described in one of the present inventions or the desulfurization method described in another of the present inventions in the purification of oil and natural gas, especially in the desulfurization of associated gas in oil fields.

[0027] The beneficial effects of this invention are:

[0028] To address the shortcomings of existing amine-based desulfurization methods, such as the inability to simultaneously and efficiently absorb sulfur-containing compounds like hydrogen sulfide, mercaptans, thioethers, carbonyl sulfides, and thiophene, and the severe foaming of the amine solution due to the absorption of heavy hydrocarbons leading to liquid backflow and tower overflow, which damages desulfurization facilities and renders them unsafe to operate, resulting in low desulfurization efficiency, this invention provides an absorbent and a desulfurization method using it. The absorbent provided by this invention comprises alkanolamine compounds, ionic liquids, and polyols. The ionic liquids and polyols exhibit a synergistic effect, working in conjunction with alkanolamine compounds to achieve efficient absorption of sulfur-containing compounds such as hydrogen sulfide, mercaptans, thioethers, carbonyl sulfides, and thiophene from associated gas in oil fields. Simultaneously, it avoids the absorption of heavy hydrocarbon components in associated gas, preventing liquid backflow and tower overflow caused by absorbent foaming. This method features a wide range of raw material sources, is pollution-free, regenerable, and has a low loss rate. The desulfurization method using the absorbent provided by this invention achieves efficient use and regeneration of the absorbent by setting the treatment conditions in the desulfurization tower and the regeneration tower. The total sulfur content of the regenerated absorbent obtained after using the method provided by this invention can be less than 2g / L. Detailed Implementation

[0029] The present invention will be further described below with reference to the embodiments. However, the embodiments of the present invention are merely illustrative examples and should not be construed as limiting the present invention under any circumstances.

[0030] The associated gas composition involved in the following embodiments is shown in Tables 1 and 2:

[0031] Table 1. Results of hydrocarbon analysis of associated gas monomers

[0032] Components Volume fraction / % (v) Components Volume fraction / % (v) <![CDATA[N2]]> 4.17 <![CDATA[n-C4]]> 3.14 <![CDATA[CO2]]> 3.52 <![CDATA[i-C5]]> 2.53 <![CDATA[C1]]> 56.48 <![CDATA[n-C5]]> 1.17 <![CDATA[C2]]> 15.63 <![CDATA[C 6+ ]]> 1.84 <![CDATA[C3]]> 7.49 <![CDATA[H2O]]> 0.21 <![CDATA[i-C4]]> 1.98 <![CDATA[H2S]]> 1.84

[0033] Table 2. Results of sulfur analysis of associated gas monomers

[0034] Monomer sulfur <![CDATA[Content of monomer sulfur / (mg·m -3 )]]> hydrogen sulfide 18439 Methanethiol 298 Ethyl mercaptan 76 carbonyl sulfide 81 Sulfides 51 Thiophene sulfur, etc. 29

[0035] Example 1

[0036] Preparation of absorbent:

[0037] 200g of N-methyldiethanolamine, 500g of 1-methyl-3-ethylimidazolium dicyanamide salt and 300g of ethylene glycol were mixed evenly to obtain absorbent 1;

[0038] Desulfurization methods to be implemented:

[0039] 1) 100L of pressurized and separated associated gas and 1L of absorbent 1 are brought into countercurrent contact in a desulfurization tower with 30 layers of trays, which is equivalent to 10 theoretical plates. The feed temperature of the absorbent is 40℃, the feed temperature of the associated gas is 35℃, and the pressure in the desulfurization tower is 2.0MPa. The purified associated gas with hydrogen sulfide and organic sulfur removed is obtained at the top of the tower, and the absorbent liquid rich in hydrogen sulfide and organic sulfur is obtained at the bottom of the tower.

[0040] 2) The purified associated gas obtained in step 1) enters the absorption stabilization and separation unit. The absorbent enters a regeneration tower with 30 trays (equivalent to 10 theoretical trays), with the feed point at the fourth tray. The pressure is atmospheric pressure, the top temperature is 105℃, and the bottom temperature is 152℃. All the liquid phase at the top of the tower is refluxed, and all the non-condensable gas is extracted. The resulting regenerated absorbent is returned to the desulfurization tower for recycling. The total sulfur content of the regenerated absorbent here is less than 2g / L.

[0041] Example 2

[0042] Preparation of absorbent:

[0043] 100g of N-methyldiethanolamine, 800g of 1-methyl-3-ethylimidazolium dicyanamide salt and 100g of ethylene glycol were mixed evenly to obtain absorbent 2;

[0044] Desulfurization methods to be implemented:

[0045] Replace absorbent 1 in Example 1 with an equal volume of absorbent 2 prepared in this example, and everything else is the same as in Example 1.

[0046] Example 3

[0047] Preparation of absorbent:

[0048] 200g of N-methyldiethanolamine, 700g of 1-methyl-3-ethylimidazolium dicyanamide salt and 100g of ethylene glycol were mixed evenly to obtain absorbent 3;

[0049] Desulfurization methods to be implemented:

[0050] Replace absorbent 1 in Example 1 with an equal volume of absorbent 3 prepared in this example, and everything else is the same as in Example 1.

[0051] Example 4

[0052] Preparation of absorbent:

[0053] 100g of N-methyldiethanolamine, 700g of 1-methyl-3-ethylimidazolium dicyanamide salt and 200g of ethylene glycol were mixed evenly to obtain absorbent 4;

[0054] Desulfurization methods to be implemented:

[0055] Replace absorbent 1 in Example 1 with an equal volume of absorbent 4 prepared in this example, and everything else is the same as in Example 1.

[0056] Example 5

[0057] Preparation of absorbent:

[0058] 100g of N-methyldiethanolamine, 200g of 1-methyl-3-ethylimidazolium dicyanamide salt and 700g of ethylene glycol were mixed evenly to obtain absorbent 5;

[0059] Desulfurization methods to be implemented:

[0060] Replace absorbent 1 in Example 1 with an equal volume of absorbent 5 prepared in this example, and everything else is the same as in Example 1.

[0061] Example 6

[0062] Preparation of absorbent:

[0063] 600g of N-methyldiethanolamine, 200g of 1-methyl-3-ethylimidazolium dicyanamide salt and 200g of ethylene glycol were mixed evenly to obtain absorbent 6;

[0064] Desulfurization methods to be implemented:

[0065] Replace absorbent 1 in Example 1 with an equal volume of absorbent 6 prepared in this example, and everything else is the same as in Example 1.

[0066] Example 7

[0067] Preparation of absorbent:

[0068] 400g of N-methyldiethanolamine, 500g of 1-methyl-3-ethylimidazolium dicyanamide salt and 100g of ethylene glycol were mixed evenly to obtain absorbent 7;

[0069] Desulfurization methods to be implemented:

[0070] Replace absorbent 1 in Example 1 with an equal volume of absorbent 7 prepared in this example, and everything else is the same as in Example 1.

[0071] Example 8

[0072] Preparation of absorbent:

[0073] 400g of N-methyldiethanolamine, 400g of 1-methyl-3-ethylimidazolium dicyanamide salt and 200g of ethylene glycol were mixed evenly to obtain absorbent 8;

[0074] Desulfurization methods to be implemented:

[0075] Replace absorbent 1 in Example 1 with an equal volume of absorbent 8 prepared in this example, and everything else is the same as in Example 1.

[0076] Example 9

[0077] Preparation of absorbent:

[0078] 200g of N-methyldiethanolamine, 400g of 1-methyl-3-ethylimidazolium dicyanamide salt and 400g of ethylene glycol were mixed evenly to obtain absorbent 9;

[0079] Desulfurization methods to be implemented:

[0080] Replace absorbent 1 in Example 1 with an equal volume of absorbent 9 prepared in this example, and everything else is the same as in Example 1.

[0081] Example 10

[0082] Preparation of absorbent:

[0083] 200g of monoethanolamine, 500g of N-methyl-N-ethylpyrrole dicyandiamide salt and 300g of 1,3-propanediol were mixed evenly to obtain absorbent 10;

[0084] Desulfurization methods to be implemented:

[0085] Replace absorbent 1 in Example 1 with an equal volume of absorbent 10 prepared in this example. The number of desulfurization tower trays is 25, the absorbent feed temperature is 30°C, and other conditions are the same as in Example 1.

[0086] Example 11

[0087] Preparation of absorbent:

[0088] 200g of diethanolamine, 500g of N-methyl-N-ethylpyrrole dicyandiamide salt and 300g of 1,2-propanediol were mixed evenly to obtain absorbent 11;

[0089] Desulfurization methods to be implemented:

[0090] Replace the absorbent 1 in Example 1 with an equal volume of the absorbent 11 prepared in this example. The feed ratio of associated gas to absorbent is 300:1, the feed temperature of absorbent is 40°C, and other conditions are the same as in Example 1.

[0091] Example 12

[0092] Preparation of absorbent:

[0093] 200g of methyl monoethanolamine, 500g of N-methyl-N-ethylpyrrole dicyandiamide salt and 300g of 1,4-butanediol were mixed evenly to obtain absorbent 12;

[0094] Desulfurization methods to be implemented:

[0095] The absorbent 1 in Example 1 was replaced with an equal volume of absorbent 12 prepared in this example. The number of desulfurization tower trays was 35, the feed ratio of associated gas to absorbent was 500:1, the feed temperature of absorbent was 50°C, and other conditions were the same as in Example 1.

[0096] Comparative Example 1

[0097] Preparation of absorbent:

[0098] 500g of N-methyldiethanolamine and 500g of ethylene glycol were mixed evenly to obtain absorbent 13;

[0099] Desulfurization methods to be implemented:

[0100] Replace absorbent 1 in Example 1 with an equal volume of absorbent 13 prepared in this example, and everything else is the same as in Example 1.

[0101] Comparative Example 2

[0102] Preparation of absorbent:

[0103] 1000g of N-methyl-N-ethylpyrrole dicyandiamide salt was used directly as an absorbent to obtain absorbent 14;

[0104] Desulfurization methods to be implemented:

[0105] Replace absorbent 1 in Example 1 with an equal volume of absorbent 14 prepared in this example, and everything else is the same as in Example 1.

[0106] Comparative Example 3

[0107] Preparation of absorbent:

[0108] 1000g of 1,3-propanediol was used directly as an absorbent to obtain absorbent 15;

[0109] Desulfurization methods to be implemented:

[0110] Replace absorbent 1 in Example 1 with an equal volume of absorbent 15 prepared in this example, and everything else is the same as in Example 1.

[0111] Comparative Example 4

[0112] Preparation of absorbent:

[0113] 500g of N-methyl-N-ethylpyrrole dicyandiamide salt and 500g of 1,3-propanediol were mixed evenly to obtain absorbent 16;

[0114] Desulfurization methods to be implemented:

[0115] Replace absorbent 1 in Example 1 with an equal volume of absorbent 16 prepared in this example, and everything else is the same as in Example 1.

[0116] Comparative Example 5

[0117] Preparation of absorbent:

[0118] 200g of N-methyldiethanolamine and 500g of 1-methyl-3-ethylimidazolium dicyandiamide salt were mixed evenly to obtain absorbent 17;

[0119] Desulfurization methods to be implemented:

[0120] Replace absorbent 1 in Example 1 with an equal volume of absorbent 17 prepared in this example, and everything else is the same as in Example 1.

[0121] Experimental Evaluation

[0122] Table 3 shows the specific concentrations of hydrogen sulfide in the purified associated gas, the organic sulfur removal rate, the total sulfur content of the regenerated absorbent, and the liquid retention and tower flushing during the desulfurization process obtained in Examples 1 to 12 and Comparative Examples 1 to 5.

[0123] Table 3. Hydrogen sulfide concentration, organic sulfur removal rate, total sulfur content of regenerated absorbent, and liquid backflow during the desulfurization process in the purified associated gas.

[0124]

[0125] (Continued from Table 3)

[0126]

[0127] While the present invention has been described with reference to specific embodiments, those skilled in the art will understand that various changes can be made without departing from the true spirit and scope of the invention. Furthermore, numerous modifications can be made to the subject, spirit, and scope of the invention to suit specific situations, materials, material absorbents, and methods. All such modifications are included within the scope of the claims of the present invention.

Claims

1. An absorbent comprising an alkanolamine compound, an ionic liquid, and a polyol; The polyol is at least one of C2 to C4 diols; The ionic liquid is 1-methyl-3-ethylimidazolium dicyanamide salt and / or N-methyl-N-ethylpyrrole dicyanamide salt; Based on the mass of the absorbent, the absorbent comprises 10% to 60% alkanolamine compounds, 40% to 80% ionic liquids and 10% to 70% polyols; The alkanolamine compound is at least one of monoethanolamine, diethanolamine, methylmonoethanolamine, and N-methyldiethanolamine.

2. The absorbent according to claim 1, characterized in that, The polyol is at least one selected from ethylene glycol, 1,2-propanediol, 1,3-propanediol and 1,4-butanediol.

3. A desulfurization method, comprising the following steps: 1) The associated gas and absorbent are brought into countercurrent contact in the desulfurization tower, and the purified associated gas is obtained at the top of the tower, while the absorbent is obtained at the bottom of the tower. 2) The absorbent is discharged into a regeneration tower to obtain a regenerated absorbent; 3) The regenerated absorbent is returned to the desulfurization tower for recycling; The absorbent is the absorbent described in claim 1 or 2.

4. The method according to claim 3, characterized in that, The feed volume ratio of the associated gas and the absorbent is (100 to 500):1; and / or The total sulfur content in the regenerated absorbent is less than 2 g / L.

5. The method according to claim 3, characterized in that, In the desulfurization tower, the feed temperature of the associated gas and the feed temperature of the absorbent are each independently 30 to 50°C, and the pressure in the desulfurization tower is 0.5 to 5.0 MPa; and / or In the regeneration tower, the top temperature is 100 to 110°C, and the bottom temperature is 120 to 220°C; and / or The desulfurization tower and the regeneration tower are each independently a plate tower and / or a packed tower; and / or The number of tray layers in the desulfurization tower and the regeneration tower are each independently between 25 and 40.

6. The application of the absorbent according to claim 1 or 2 in the purification of oil and gas.

7. The application of the absorbent according to claim 1 or 2 or the desulfurization method according to any one of claims 3 to 5 in associated gas desulfurization in oil fields.

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