An environmentally friendly descaling and cleaning agent for subsea pipelines, its preparation method and application method

Abstract

This invention discloses an environmentally friendly descaling and cleaning agent for subsea pipelines, its preparation method, and its application method. The descaling and cleaning agent comprises the following components by mass percentage: Agent A: 50%–90% tetramethylolphosphine sulfate; balance water. Agent B: 1%–12% disodium ethylenediaminetetraacetate; 1%–8% thiourea; 1%–5% ammonium chloride; 0.1%–8% alcohol ether carboxylates or alcohol ether sulfates; 0.8%–11% alkylphenol polyoxyethylene ether; balance water. The descaling and cleaning agent of this application consists of two agents, has a near-neutral pH, and is an environmentally friendly descaling agent. Furthermore, this descaling and cleaning agent can effectively prevent the generation of sulfides and high-valence ferric ions, effectively controlling corrosion.

Description

Technical Field

[0001] This invention relates to the field of descaling agents, and in particular to an environmentally friendly descaling and cleaning agent for subsea pipelines, its preparation method, and its application method. Background Technology

[0002] Crude oil often contains sulfur-containing compounds such as elemental reactive sulfur, hydrogen sulfide, mercaptans, and thioethers. Upon heating, these compounds decompose to form reactive sulfur, which is highly corrosive. Therefore, ferrous sulfide scale easily forms in refining and chemical plants, particularly in distillation, catalysis, hydrogenation, gas separation, continuous reforming, wastewater stripping, sulfur recovery, heat exchangers, and desulfurization regeneration towers. However, the formation of ferrous sulfide scale in oil and gas field development is more complex. Besides corrosion caused by the quality of production water and acidic gases such as H2S and CO2 in associated gas, high sulfate content in injected water can also exacerbate corrosion through the biological metabolism of sulfate-reducing bacteria, leading to the formation of ferrous sulfide scale.

[0003] Ferrous sulfide scale differs from conventional calcium carbonate, calcium sulfate, and barium strontium sulfate scale found in oilfields. In the presence of water, ferrous sulfide scale causes more severe under-deposit corrosion, exhibiting various scaling forms with significantly different physicochemical properties, such as FeS, FeS2, Fe2S3, and Fe9S8, and often coexisting with scales such as ferric carbonate and ferric oxide. Furthermore, the large contact angle of ferrous sulfide scale makes it easily encapsulated by oil, affecting the dissolution efficiency of cleaning agents. Ferrous sulfide scale also possesses high flammability; upon contact with air, it rapidly undergoes an exothermic oxidation reaction, potentially leading to fires and explosions.

[0004] The conventional method for treating and cleaning ferrous sulfide scale is acid washing, with hydrochloric acid having the highest dissolving efficiency. However, ferrous sulfide scale reacts with acid to produce hydrogen sulfide gas. This hydrogen sulfide gas generated during acid washing not only has a foul odor and is toxic, but it is also flammable and explosive. Furthermore, the hydrogen sulfide gas forms an aqueous solution in the acid washing solution, which is extremely corrosive. Improper control can easily lead to serious acid washing corrosion accidents. In addition, corrosion control during the cleaning of ferrous sulfide scale is very difficult. On one hand, the pH value of the system gradually decreases during the cleaning process, causing acid corrosion. The slowly released hydrogen sulfide gas dissolves in water, not only exacerbating acid corrosion but also easily leading to stress cracking corrosion caused by sulfides. Simultaneously, the high-valence ferric ions removed during cleaning can form galvanic cells with the metal substrate, leading to electrochemical corrosion of the metal. Summary of the Invention

[0005] In order to solve the above-mentioned technical problems, the present invention provides an environmentally friendly descaling and cleaning agent for subsea pipelines, as well as its preparation and application methods.

[0006] In a first aspect, the present invention provides an environmentally friendly descaling and cleaning agent for subsea pipelines, which is achieved by the following technical solution.

[0007] An environmentally friendly descaling and cleaning agent for subsea pipelines comprises the following components by weight percentage:

[0008] Agent A: 50%–90% tetramethylphosphonic acid sulfate; the remainder is water;

[0009] Agent B: Disodium ethylenediaminetetraacetate 1%–12%; thiourea 1%–8%; ammonium chloride 1%–5%; alcohol ether carboxylates or alcohol ether sulfates 0.1%–8%; alkylphenol polyoxyethylene ethers 0.8%–11%; balance is water.

[0010] By adopting the above technical solution, during cleaning operations, the combined use of Agent A and Agent B of this application forms a composite chelating system that chelates and dissolves ferrous sulfide while slowly releasing hydrogen ions, further dissolving the carbonate scale mixed in the scale sample. The descaling cleaning agent of this application can react with ferrous sulfide to form a water-soluble complex, fully dissolving the target scale sample without secondary precipitation or significant hydrogen sulfide gas leakage. Simultaneously, it alters the surface characteristics of the scale sample, allowing the agent to rapidly diffuse and penetrate the scale surface.

[0011] Furthermore, an environmentally friendly subsea pipeline descaling and cleaning agent comprises the following components by weight percentage:

[0012] Agent A: 70% tetramethylphosphonic acid sulfate; the remainder is water;

[0013] Agent B: 2% disodium ethylenediaminetetraacetate; 1.7% thiourea; 1.8% ammonium chloride; 0.8% alcohol ether carboxylate or alcohol ether sulfate; 2% alkylphenol polyoxyethylene ether; balance is water.

[0014] Furthermore, the alcohol ether carboxylate is selected from sodium fatty alcohol polyoxyethylene ether carboxylate; the alcohol ether sulfate is selected from sodium fatty alcohol polyoxyethylene ether sulfate.

[0015] Furthermore, the alkylphenol polyoxyethylene ether is selected from polyoxyethylene octylphenol ether-9.

[0016] Furthermore, the pH value of the descaling cleaning agent is near neutral.

[0017] Furthermore, Agent A and Agent B need to be prepared and stored separately.

[0018] Secondly, the present invention provides a method for preparing an environmentally friendly descaling and cleaning agent for subsea pipelines, which is achieved by the following technical solution.

[0019] A method for preparing the above-mentioned environmentally friendly subsea pipeline descaling and cleaning agent includes the following steps:

[0020] S1. Heat the water according to the formula to 40-45℃, add tetramethylolphosphine sulfate according to the formula, and stir slowly until it is completely dissolved to obtain Agent A;

[0021] S2. Place alcohol ether carboxylates or alcohol ether sulfates and alkylphenol polyoxyethylene ethers at 30-50°C for 10-24 hours;

[0022] S3. Heat a certain amount of water to 40-45℃, add alcohol ether carboxylate or alcohol ether sulfate and disodium ethylenediaminetetraacetate according to the formula, and stir slowly until completely dissolved.

[0023] S4. Add a certain amount of water to the solution obtained in step S3, and at 40-45°C, add thiourea, ammonium chloride and alkylphenol polyoxyethylene ether according to the formula amount, and stir slowly until they are completely dissolved.

[0024] S5. Add a certain amount of water to the solution obtained in step S4 to reach the amount of water required for the formulation of agent B and stir thoroughly;

[0025] S6. Cool to below 30°C to obtain agent B.

[0026] Thirdly, the present invention provides a method for using an environmentally friendly descaling and cleaning agent for subsea pipelines, which is achieved by the following technical solution.

[0027] A method for using the above-mentioned environmentally friendly subsea pipeline descaling and cleaning agent, wherein the descaling and cleaning agent includes agent A and agent B, and agent A, agent B and water are prepared and used immediately before use in a mass ratio of 1:(4-5):(4-5).

[0028] Furthermore, on-site mixing involves either mixing the reagents thoroughly in a reagent tank before adding them to the system to be cleaned, or adding them directly to the system to be cleaned using a metering pump in proportion.

[0029] Furthermore, softened water or clean tap water should be used for mixing; if other water sources are used, compatibility tests should be conducted in advance.

[0030] This application has the following beneficial effects.

[0031] The descaling agent of this application can directly react with ferrous sulfide to form a water-soluble chelate, effectively controlling the generation of free hydrogen sulfide and iron ions. Simultaneously, a highly efficient corrosion inhibitor system has been developed, thereby achieving ideal corrosion control. Considering environmental protection, transportation, and construction safety, this application has determined a development route for an environmentally friendly descaling agent based on a highly efficient iron ion chelating agent, which can control the release of hydrogen sulfide gas while dissolving scale. Detailed Implementation

[0032] The present invention will be further described below with reference to embodiments.

[0033] The sodium fatty alcohol polyoxyethylene ether carboxylate in this embodiment was purchased from Nantong Chenrun Chemical Co., Ltd., and its model is AEC-9Na.

[0034] The polyoxyethylene octylphenol ether-9 in this embodiment was purchased from Nantong Chenrun Chemical Co., Ltd., and its model is OP-9.

[0035] Example 1

[0036] An environmentally friendly descaling and cleaning agent for subsea pipelines comprises the following components by weight percentage:

[0037] Agent A: 7 kg tetramethylphosphonic acid sulfate; 3 kg water. (This is an aqueous solution with an effective content of approximately 70%)

[0038] Agent B: 2 kg of disodium ethylenediaminetetraacetate; 1.7 kg of thiourea; 1.8 kg of ammonium chloride; 0.8 kg of sodium fatty alcohol polyoxyethylene ether carboxylate; 92 kg of polyoxyethylene octylphenol ether; 91.7 kg of water.

[0039] A method for preparing an environmentally friendly descaling and cleaning agent for subsea pipelines includes the following steps:

[0040] 1) Add 3 kg of water to the reactor and heat to 45°C, then add 7 kg of tetramethylolphosphine sulfate and stir slowly until completely dissolved to obtain Agent A;

[0041] 2) Place sodium fatty alcohol polyoxyethylene ether carboxylate and polyoxyethylene octylphenol ether-9 in a 45°C warm room for 12 hours.

[0042] 3) Add 15kg of water to the reactor and heat to 45℃. Add sodium fatty alcohol polyoxyethylene ether carboxylate and disodium ethylenediaminetetraacetate according to the formula and stir slowly until they are completely dissolved.

[0043] 4) Add 25kg of water to the reactor. When the temperature rises to 45℃, add thiourea, ammonium chloride and polyoxyethylene octylphenol ether-9 according to the formula, and stir slowly until they are completely dissolved.

[0044] 5) Add 51.7 kg of water to the reactor and stir thoroughly;

[0045] 6) Cool to below 30℃, take samples for testing, and discharge the material after passing the test to obtain agent B;

[0046] 7) Error range of feeding amount: ±0.5kg of feeding amount.

[0047] When using, mix agent A, agent B, and water in a volume ratio of 1:4.5:4.5 and use immediately.

[0048] Example 2

[0049] An environmentally friendly descaling and cleaning agent for subsea pipelines comprises the following components by weight percentage:

[0050] Agent A: 9 kg of tetramethylphosphonic acid; 1 kg of water.

[0051] Agent B: 2 kg of disodium ethylenediaminetetraacetate; 1.7 kg of thiourea; 1.8 kg of ammonium chloride; 0.8 kg of sodium fatty alcohol polyoxyethylene ether carboxylate; 92 kg of polyoxyethylene octylphenol ether; 91.7 kg of water.

[0052] The preparation method of the environmentally friendly subsea pipeline descaling and cleaning agent is the same as in Example 1.

[0053] When using, mix agent A, agent B, and water in a volume ratio of 1:4.5:4.5 and use immediately.

[0054] Example 3

[0055] An environmentally friendly descaling and cleaning agent for subsea pipelines comprises the following components by weight percentage:

[0056] Agent A: 5 kg of tetramethylphosphonic acid; 5 kg of water.

[0057] Agent B: 2 kg of disodium ethylenediaminetetraacetate; 1.7 kg of thiourea; 1.8 kg of ammonium chloride; 0.8 kg of sodium fatty alcohol polyoxyethylene ether carboxylate; 92 kg of polyoxyethylene octylphenol ether; 91.7 kg of water.

[0058] The preparation method of the environmentally friendly subsea pipeline descaling and cleaning agent is the same as in Example 1.

[0059] When using, mix agent A, agent B, and water in a volume ratio of 1:5:5 and use immediately.

[0060] Comparative Example 1

[0061] A descaling and cleaning agent for subsea pipelines comprises the following components by weight percentage:

[0062] 10 kg of aminosulfonic acid; 1 kg of HEDP; 89 kg of water.

[0063] Performance testing

[0064] 1. Physical performance testing

[0065] The physical properties of the descaling cleaning agents prepared in Examples 1-3 of this application are shown in Table 1.

[0066] Table 1

[0067] Descaling cleaning agents / projects Technical indicators Remark Solubility Easily soluble in water Original solution pH 7.0±1.5 Original solution Corrosion rate of chemical solution <![CDATA[≤0.35mm / a(0.3132g / m 2 / h)]]> Use concentration Flash point >60℃ Original solution Descaling rate ≥95％ Use concentration Safety / Environmental friendliness Free of ODS and VOCs Original solution

[0068] 2. Determination of descaling rate

[0069] Accurately weigh 2.00 g of the dried scale sample, add 200 g of cleaning agent sample, seal, and place in a 50℃ water bath for 24 hours. Remove, filter while hot, and thoroughly rinse the test bottle and scale sample with distilled water. Dry the remaining scale sample in a 100-105℃ constant temperature drying oven to constant weight. The descaling rate of the cleaning agent is expressed as the percentage of dissolved scale mass to the original scale mass. Experimental results are shown in Table 2.

[0070] Table 2

[0071]

[0072] 3. Determination of corrosion rate

[0073] At 50℃ for 6 hours, the corrosion rate on X65 metal is less than 0.35 mm / a (0.3132 g / m³). 2 / h), the metal surface is smooth and free of pitting corrosion, and the corrosion control is superior to the corrosion rate requirement for stainless steel in SH-T 3547-2011 "Specification for Chemical Cleaning Construction and Acceptance of Petrochemical Equipment and Pipelines" (≤2g / m). 2 / h) and the requirements for the corrosion rate of stainless steel materials in the GB-T 25146-2010 "Quality Acceptance Specification for Chemical Cleaning of Industrial Equipment" (≤1g / m) for laboratory verification. 2 / h). The experimental results are shown in Table 3.

[0074] Table 3

[0075] <![CDATA[Corrosion rate (g / m 2 / h)]]> Example 1 0.266 Example 2 0.267 Example 3 0.289 Comparative Example 1 0.875

[0076] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An environmentally friendly descaling and cleaning agent for subsea pipelines, characterized in that: Components including the following mass percentages: Agent A: Tetramethylphosphonic acid 50%~90%; the remainder is water; Agent B: Disodium ethylenediaminetetraacetate 1%~12%; thiourea 1%~8%; ammonium chloride 1%~5%; alcohol ether carboxylates or alcohol ether sulfates 0.1%~8%; alkylphenol polyoxyethylene ethers 0.8%~11%; balance is water; Before using the environmentally friendly subsea pipeline descaling and cleaning agent, prepare the mixture of agent A, agent B, and water in a mass ratio of 1:(4~5):(4~5) and use it immediately.

2. The environmentally friendly descaling and cleaning agent for subsea pipelines according to claim 1, characterized in that: Components including the following mass percentages: Agent A: 70% tetramethylphosphonic acid; the remainder is water; Agent B: Disodium ethylenediaminetetraacetate 2%; thiourea 1.7%; ammonium chloride 1.8%; alcohol ether carboxylates or alcohol ether sulfates 0.8%; alkylphenol polyoxyethylene ether 2%; balance is water.

3. The environmentally friendly descaling and cleaning agent for subsea pipelines according to claim 1 or 2, characterized in that: The alcohol ether carboxylate is selected from sodium fatty alcohol polyoxyethylene ether carboxylate; the alcohol ether sulfate is selected from sodium fatty alcohol polyoxyethylene ether sulfate.

4. The environmentally friendly descaling and cleaning agent for subsea pipelines according to claim 1 or 2, characterized in that: The alkylphenol polyoxyethylene ether is selected from polyoxyethylene octylphenol ether-9.

5. A method for preparing an environmentally friendly descaling and cleaning agent for subsea pipelines according to any one of claims 1-4, characterized in that: Includes the following steps: S1. Heat the water according to the formula to 40~45℃, add tetramethylolphosphine sulfate according to the formula, and stir slowly until it is completely dissolved to obtain agent A; S2. Place the alcohol ether carboxylate or alcohol ether sulfate and alkylphenol polyoxyethylene ether at 30-50°C for 10-24 hours; S3. Heat a certain amount of water to 40~45℃, add alcohol ether carboxylate or alcohol ether sulfate and disodium ethylenediaminetetraacetate according to the formula, and stir slowly until completely dissolved. S4. Add a certain amount of water to the solution obtained in step S3, and at 40~45℃, add alkylphenol polyoxyethylene ether, thiourea and ammonium chloride according to the formula amount, and stir slowly until they are completely dissolved. S5. Add a certain amount of water to the solution obtained in step S4 to reach the amount of water required for the formulation of agent B and stir thoroughly; S6. Cool to below 30°C to obtain agent B.

6. A method of using the environmentally friendly descaling and cleaning agent for subsea pipelines as described in any one of claims 1-4, characterized in that: The descaling cleaning agent includes Agent A and Agent B. Agent A, Agent B and water should be prepared and used immediately before use in a mass ratio of 1:(4~5):(4~5).

7. The method of using the environmentally friendly descaling and cleaning agent for subsea pipelines according to claim 6, characterized in that: On-site mixing involves either mixing the reagents thoroughly in a reagent tank before adding them to the system to be cleaned, or adding them directly to the system to be cleaned using a metering pump in proportion.

8. The method of using the environmentally friendly descaling and cleaning agent for subsea pipelines according to claim 6, characterized in that: Softened water or clean tap water should be used for mixing; if other water sources are used, a compatibility test should be conducted in advance.

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