An absorbent for removing H2S from low-sulfur gases

Abstract

This invention belongs to the field of gas purification, specifically relating to an absorbent for removing H2S from low-sulfur gases. It comprises triazine, hindered amine, additives, and water. The concentrations of triazine, hindered amine, and additives are 5–10% (wt), respectively, with the remainder being water. The absorbent of this invention can effectively remove H2S from low-sulfur natural gas or associated gas from oil fields. With a feed gas pressure of 1–5 MPa, a temperature of 35–70°C, and H2S concentration of 0.1–1%v, the purified gas has an H2S content ≤6 mg / Nm3, meeting the purification gas standards. This absorbent has a higher sulfur capacity and requires less dosage than traditional absorbents, while also exhibiting scale inhibition properties.

Description

Technical Field

[0001] This invention belongs to the field of gas purification and relates to an absorbent for removing H2S from low-sulfur gases, particularly an absorbent for removing H2S from low-sulfur natural gas or associated gas from oil fields. Background Technology

[0002] Currently, domestic and foreign companies have mature technologies for the removal of high-acid gases, but these technologies have drawbacks such as high investment costs, complex processes, and large land area requirements, and are not suitable for low-sulfur gas wells.

[0003] Liquid hydrogen sulfide absorbent can be directly injected into the gas wellbore, which has the advantages of convenient operation, low cost and no impact on the daily production of gas wells. It is suitable for desulfurization of gas wells with small footprint, dispersed well locations and low hydrogen sulfide gas content.

[0004] Therefore, for H2S removal from low-H2S natural gas or associated gas from oil fields, it is necessary to develop and use desulfurization agents and related processes that differ from traditional absorption methods.

[0005] Triazine liquid desulfurizers have become the preferred technology for removing low concentrations of hydrogen sulfide. 1,3,5-tris(2-hydroxyethyl)-hexahydrotriazine is widely used for hydrogen sulfide removal due to its high absorption efficiency, low dosage, fast speed, and low pollution of absorption products. However, it is prone to scaling and pipeline corrosion. Summary of the Invention

[0006] The purpose of this invention is to provide an absorbent for removing H2S from low-sulfur gases, particularly for removing H2S from low-sulfur natural gas or associated gas from oil fields. This absorbent has better H2S absorption efficiency than traditional absorbents, requires a much smaller dosage, and also exhibits scale inhibition properties.

[0007] The main technical solution of the present invention is an absorbent for removing H2S from low sulfur-containing gases, characterized in that the desulfurization absorbent contains triazine, hindered amine, additives, and water; wherein the concentration of triazine is 5-10% (wt), the concentration of hindered amine is 5-10% (wt), the concentration of additives is 0.1-2% (wt), and the remainder is water.

[0008] Preferably, the triazine concentration is 5-8% (wt).

[0009] The triazine is 1,3,5-tris(2-hydroxyethyl)-hexahydrotriazine.

[0010] The hindered amine is selected from alicyclic organic amines.

[0011] The hindered amine is selected from piperazine and morpholine.

[0012] The hindered amine contains 1-5% (wt) piperazine and 1-5% (wt) morpholine in the absorbent.

[0013] The additive is an organophosphonate.

[0014] Generally, the H2S content in the low-sulfur gas described in this invention is 0.1~1%v.

[0015] The low-sulfur gas is low-sulfur natural gas or associated gas from oil fields.

[0016] The low-sulfur natural gas or associated gas from the oil field has a pressure of 1~5MPa and a temperature of 35~70℃.

[0017] Compared with traditional decarbonization absorbents, this invention has the following significant advantages: better desulfurization effect, lower dosage, and scale inhibition properties, thereby improving economic efficiency. Detailed Implementation

[0018] The present invention will now be described in detail with reference to embodiments, but is not limited to the contents described in the following embodiments.

[0019] Sulfur capacity determination: The feed gas was a mixture of H2S and N2, with an H2S volume fraction of 0.1%, a pressure of 3 MPa, and a temperature of 40℃. 300 ml of the prepared desulfurizing agent in different proportions was added to the chamber of a high-pressure reactor. The temperature of the absorbent liquid in the reactor was controlled by heat transfer oil in the jacket. Sulfur capacity was determined by bubbling H2S-containing gas. During the experiment, the feed gas flow rate was 600 mL / min, and a 2% (w / w) zinc acetate solution was introduced into the purified gas outlet. Timing started when the feed gas was introduced and stopped when the zinc acetate solution turned noticeably white.

[0020] Scale inhibition performance test: Scale is mainly of the CaCO3 type. Scale inhibition performance was tested according to GB / T 16632-2019 "Determination of Scale Inhibition Performance of Water Treatment Agents - Calcium Carbonate Deposition Method". Operating procedure: A test solution was prepared by mixing water containing a certain amount of bicarbonate and calcium ions with the scale inhibitor. The solution was then heated to 80±1℃ to accelerate the decomposition of calcium bicarbonate into calcium carbonate. After reaching equilibrium, the calcium ion concentration was measured. The higher the calcium ion concentration, the better the scale inhibition performance of the scale inhibitor. The scale inhibition performance of the triazine liquid desulfurizer is expressed as η (inclusive), with the value expressed as a percentage, and calculated using the following formula:

[0021] η= ×100%

[0022] In the formula:

[0023] ρ0 — The numerical value of calcium ion mass concentration in the prepared water sample, in mg / mL.

[0024] ρ1—The mass concentration of calcium ions in the water sample without added triazine liquid desulfurizer, in mg / mL.

[0025] ρ2 — The mass concentration of calcium ions in the water sample prepared with added triazine liquid desulfurizer, in mg / mL.

[0026] ① To prepare a standard sodium bicarbonate solution, 1 mL contains approximately 18.3 mg of HCO3. - and 1 mL of approximately 6 mg of Ca 2+ Calcium chloride standard solution;

[0027] ② Prepare approximately 0.1 mol / L hydrochloric acid standard titration solution and approximately 0.01 mol / L sodium ethylenediaminetetraacetate (EDTA) standard titration solution, as well as borax buffer solution with a pH of approximately 9, bromocresol green-methyl red indicator solution and calcium-carboxylic acid indicator;

[0028] ③ Preparation of calcium ion-containing water sample for the test of adding triazine liquid desulfurizer: Add 250 mL of water to a 500 mL volumetric flask, add a certain volume of calcium chloride standard solution using a burette to make the amount of calcium ions 120 mg; add a certain amount of liquid triazine desulfurizer using a pipette and shake well; then add 20 mL of borax buffer solution and shake well; slowly add a certain volume of sodium bicarbonate standard solution using a burette to make the amount of bicarbonate ions 366 mg, dilute with water to the mark, and shake well;

[0029] ④ Prepare a blank test sample containing calcium ions: The process is the same as ③, except that no liquid desulfurizing agent is added;

[0030] ⑤ Place the test and blank test containing triazine liquid desulfurizer in two clean conical flasks, respectively, and immerse them in a constant temperature water bath at 80±1℃ for 10 hours. After the test, filter the solution while it is still hot using medium-speed quantitative filter paper. After the filtrate cools, take 25 mL of the filtrate into a conical flask, add water to about 80 mL, add 5 mL of 200 g / L potassium hydroxide solution and about 0.1 g of calcium-carboxylic acid indicator. Titrate the solution with EDTA standard solution until the solution changes from purple-red to bright blue, which is the endpoint. Calculate the calcium ion concentration in the test and blank test containing triazine liquid desulfurizer, and calculate the scale inhibition rate using the formula above.

[0031] Table 1. Absorbent formulation of examples

[0032]

[0033] (1) Determination of the absorption of triazine

[0034] Table 2. Sulfur capacity of triazine desulfurizer

[0035]

[0036] (2) Determination of scale inhibition rate of triazine

[0037] Table 3 Scale inhibition rate test results

[0038] Serial Number scale inhibition rate Example 1 47.8% Example 2 67.9% Example 3 72.5% Example 4 74.4% Example 5 70.4% Example 6 67.3%

[0039] The data from the examples show that, compared with the single triazine absorbent (Example 1), the absorbent (Examples 2-6) has a larger sulfur capacity and requires less dosage than the traditional absorbent, while also having scale inhibition properties.

Claims

1. An absorbent for removing H2S from low-sulfur gases, characterized in that... The desulfurization absorbent contains triazine, hindered amine, additives, and water; wherein the concentration of triazine is 5-10% wt, the concentration of hindered amine is 5-10% wt, the concentration of additives is 0.1-2% wt, and the remainder is water; the hindered amine is selected from piperazine and morpholine, with piperazine accounting for 1-5% wt and morpholine accounting for 1-5% wt in the absorbent; the low-sulfur gas is low-sulfur natural gas or associated gas from oil fields with an H2S content of 0.1-1%v, at a pressure of 1-5 MPa and a temperature of 35-70℃.

2. The absorbent liquid according to claim 1, characterized in that... The concentration of the triazine is 5–8% wt.

3. The absorbent liquid according to claim 1, characterized in that... The triazine is 1,3,5-tris(2-hydroxyethyl)-hexahydrotriazine.

4. The absorbent liquid according to claim 1, characterized in that... The additive is an organophosphonate.

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