Polythionate corrosion inhibitor and application thereof

Abstract

The invention discloses a polythionate corrosion inhibitor for sulfur-containing high-temperature equipment. The inhibitor is composed of a viscous agent and effective components, and a protective film is formed by coating the surface of equipment, so that the problem of polythionate corrosion during storage of high-temperature sulfur-containing equipment is solved.

Description

Technical Field

[0001] This invention belongs to the field of equipment corrosion protection technology, specifically relating to a polythionic acid corrosion inhibitor and its application. Background Technology

[0002] In high-temperature equipment containing sulfur, such as our company's cracking furnace tubes and dehydrogenation reactor screens, as well as hydrocracking units and atmospheric and vacuum distillation units in the industry, metal sulfides will form on the surface of the equipment under high-temperature conditions. The corrosion products of sulfides on the surface of metal equipment are prone to generating polythionic acid, which in turn leads to stress corrosion cracking of equipment made of materials such as austenitic stainless steel, posing a serious threat to the safety and service life of the equipment.

[0003] Currently, common protective measures include immediately flushing the equipment with alkaline solution after shutdown and nitrogen protection. However, these methods have certain limitations in actual operation. For example, alkaline flushing may result in incomplete flushing and difficulty in fully contacting complex internal parts of the equipment. Nitrogen protection requires a continuous gas supply and strict sealing conditions, which is cumbersome and costly.

[0004] Among existing patented technologies, few methods are directly applicable. CN115925438B discloses a method for preparing a high-temperature resistant and corrosion-resistant composite coating for RTOs, mainly used for protection of equipment exposed to corrosive media at high temperatures, but its effectiveness against polythionyl sulfuric acid corrosion is not clearly stated; furthermore, in reactor environments, if flaking or reaction with the reaction medium occurs, it will affect the operation of the equipment. CN107829094A discloses a sulfur-resistant and high-temperature corrosion inhibitor and its preparation method, mainly targeting the corrosion of metal equipment by acidic gases such as sulfur dioxide and carbon dioxide in highly acidic oil and gas fields, but its applicability to corrosion protection caused by polythionyl sulfuric acid is insufficient. CN117487411B discloses an alloy coating resistant to hot corrosion of high-sulfur coal ash, its preparation method, and its coating process. This coating addresses the issue of wear and hot corrosion on the heated surfaces of boiler tubes during operation, which are prone to occur in power plant boilers where high-sulfur coal is widely used. It is a surface protection measure for equipment and is primarily applied to high-temperature corrosive environments such as boilers where sulfur-containing coal particles cause erosion and wear. However, it is not highly suitable for polythionine corrosion in high-temperature sulfur-containing equipment and poses a risk of flaking or reaction with the reaction medium if used in reactors or similar environments, potentially affecting the operation of the equipment. Summary of the Invention

[0005] The purpose of this invention is to provide a polythionic acid corrosion inhibitor for sulfur-containing high-temperature equipment and its application, so as to solve the problems of complex operation and limited application scenarios in the prior art.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a polythionite corrosion inhibitor, comprising an adhesive and an active ingredient.

[0008] Preferably, the adhesive of the present invention comprises at least one of sodium carboxymethyl cellulose, glycerin, polyethylene glycol, and silicone oil mixed with water. The adhesive is capable of forming a viscous adhesion and retaining moisture, adhering to the surface of the equipment and providing a function of maintaining humidity.

[0009] As a preferred embodiment of the present invention, the adhesive is a mixture of sodium hydroxymethyl cellulose, glycerin, polyethylene glycol and water.

[0010] The molecular weight of polyethylene glycol is preferably 300-3000, more preferably 500-2500. Lower molecular weight polyethylene glycol can provide good water solubility and hygroscopicity, and has a certain viscosity.

[0011] The viscosity of the silicone oil is preferably 100-500 mPa·s, and more preferably 300-500 mPa·s.

[0012] Preferably, the active ingredient of the present invention includes one or more alkaline active ingredients such as ammonium bicarbonate, sodium bicarbonate, hexamethylenediamine, triethylamine, and ethanolamine, and is preferably at least one of ammonium bicarbonate and hexamethylenediamine. This active ingredient can form a weakly alkaline environment with water in the adhesive without causing equipment corrosion.

[0013] As a preferred embodiment of the present invention, the active ingredient is a mixture of ammonium bicarbonate and hexamethylenediamine.

[0014] As a preferred embodiment of the present invention, in the polythionite corrosion inhibitor of the present invention, based on the total mass of the polythionite corrosion inhibitor, the content of sodium carboxymethyl cellulose is 0.2-2.5%, the content of glycerol is 5-15%, the content of polyethylene glycol is 10-25%, the content of active ingredient is 10-30%, and the remainder is water.

[0015] Preferably, when the active ingredients are ammonium bicarbonate and hexamethylenediamine, the mass ratio of the two is 1-2:1-4.

[0016] Secondly, a method for preparing the above-mentioned polythionite corrosion inhibitor is provided, comprising the following steps: dissolving sodium carboxymethyl cellulose in water, adding glycerol and polyethylene glycol, and then mixing it evenly with the aqueous solution of the active ingredient to obtain the polythionite corrosion inhibitor.

[0017] In the preparation method described in this invention, the mixing process is always accompanied by stirring, which helps to achieve better compatibility.

[0018] In the preparation method of this invention, the aqueous solution of the active ingredient is an aqueous solution of ammonium bicarbonate and / or hexamethylenediamine, which is obtained by mixing ammonium bicarbonate and / or hexamethylenediamine with an appropriate amount of water. The concentration of the aqueous solution of the active ingredient is not particularly limited, as long as it achieves the purpose of dissolving the active ingredient and the final content of each component meets the aforementioned requirements.

[0019] Thirdly, the application of the aforementioned polythionine corrosion inhibitor is provided.

[0020] The present invention provides a method for using the above-mentioned polythionine corrosion inhibitor. Before storing sulfur-containing high-temperature equipment, the corrosion inhibitor is uniformly coated on the surface of the equipment to form a protective film to prevent polythionine corrosion.

[0021] In the present invention, the sulfur-containing high-temperature equipment can be specifically exemplified by reactor screens and expansion joints in propane dehydrogenation (PDH) units, reactors in hydrocracking units, and other equipment that operates in a high-temperature hydrogen sulfide environment for extended periods. After a single operating cycle, this sulfur-containing high-temperature equipment is disassembled for inspection and maintenance as needed for unit repairs, and may be stored for extended periods. Because of its operation in a high-temperature hydrogen sulfide environment, these devices develop a significant amount of ferrous sulfide and other metallic sulfides on their surfaces, which are prone to long-term polythionine corrosion.

[0022] Based on this background, the present invention provides a method for using polythionine corrosion inhibitor, that is, no special cleaning is required during long-term storage. The polythionine corrosion inhibitor described in the present invention is applied to the surface of the disassembled equipment before storage. After storage, no further post-treatment such as removal of corrosion products or repair of corrosion sites is required.

[0023] Preferably, the coating method can be brushing, dipping, or other methods, with the aim of uniformly covering the equipment surface with a layer of polythionyl sulfide corrosion inhibitor to form a protective film; preferably, the coating thickness of the corrosion inhibitor is based on the ability to uniformly cover the surface, and is recommended to be 1mm-5mm, in order to prevent polythionyl sulfide corrosion.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention provides a polythionyl sulfide corrosion inhibitor. This corrosion inhibitor is easy to use; simply apply it to the equipment surface to form a protective film, effectively preventing corrosion from polythionyl sulfide. The polythionyl sulfide corrosion inhibitor of this invention effectively retains moisture and maintains alkalinity, providing a longer-lasting anti-corrosion effect, while avoiding the problems of complex operation and limited application scenarios existing in prior art. Attached Figure Description

[0026] Figure 1 Here are macroscopic surface images of the sample from Example 1 after 30 days of storage;

[0027] Figure 2 These are microscopic surface images of the sample from Example 1 after 30 days of storage.

[0028] Figure 3 These are macroscopic surface images of the sample from Example 2 after 30 days of storage.

[0029] Figure 4 These are microscopic surface images of the sample from Example 2 after 30 days of storage.

[0030] Figure 5 Macroscopic surface images of Comparative Example 1 sample after 30 days of storage;

[0031] Figure 6 The image shows the microscopic surface of the sample from Comparative Example 1 after 30 days of storage. Detailed Implementation

[0032] Main testing methods and instruments

[0033] Sample source: 347H material equipment that has been in long-term service in a high-temperature hydrogen sulfide environment, cut into 1cm pieces. 2 The samples were used for example and comparative tests.

[0034] The equipment used is:

[0035] Camera, used for taking macroscopic photographs;

[0036] Metallurgical microscope (Zeiss Lab.a1) is used for microscopic surface observation.

[0037] Example 1

[0038] Add 1g of sodium carboxymethyl cellulose to 50g of deionized water under stirring, and stir until completely dissolved; add 10g of glycerol and 20g of polyethylene glycol (molecular weight approximately 1200), and continue stirring until homogeneous; dissolve 10g of ammonium bicarbonate and 10g of hexamethylenediamine in 30g of deionized water; mix the two parts thoroughly to obtain the corrosion inhibitor.

[0039] The obtained corrosion inhibitor was evenly coated onto the sample surface to a thickness of approximately 2 mm. After storing the sample in a constant temperature and humidity environment (25℃, 60% humidity) for 30 days, the surface corrosion inhibitor was peeled off, and the sample was observed. Figure 1 , Figure 2 As shown, no obvious corrosion products such as iron oxide formed by polythionite corrosion are visible on the macroscopic surface of the sample. Microscopic observation shows no rust spots on the sample surface, indicating that the sample has not undergone polythionite corrosion.

[0040] Example 2

[0041] Add 2.5g of sodium carboxymethyl cellulose to 50g of deionized water under stirring, and stir until completely dissolved; add 25g of glycerol and 40g of polyethylene glycol (molecular weight approximately 1500), and continue stirring until homogeneous; dissolve 15g of ammonium bicarbonate and 35g of hexamethylenediamine in 40g of deionized water; mix the two parts thoroughly to obtain the corrosion inhibitor.

[0042] The obtained corrosion inhibitor was evenly coated onto the sample surface to a thickness of approximately 3 mm. After storing the sample in a constant temperature and humidity environment (25℃, 60% humidity) for 30 days, the surface corrosion inhibitor was peeled off, and the sample was observed. Figure 2 , 3 As shown, no obvious corrosion products such as iron oxide formed by polythionite corrosion are visible on the macroscopic surface of the sample. Microscopic observation shows no rust spots on the sample surface, indicating that the sample has not undergone polythionite corrosion.

[0043] Comparative Example 1

[0044] After storing the sample in a constant temperature and humidity (25℃, 60% humidity) air environment for 30 days, observations were conducted. Figure 4 , 5 As shown, reddish-brown corrosion marks appeared on the surface, and a large number of rust spots could be seen under microscopic observation. These are corrosion byproducts such as iron oxide formed after polythionite corrosion, indicating that the sample underwent polythionite corrosion without protection.

Claims

1. A polythionite corrosion inhibitor, characterized in that, The inhibitor comprises an adhesive and an active ingredient. The adhesive comprises at least one of sodium carboxymethyl cellulose, glycerin, polyethylene glycol, and silicone oil mixed with water. The active ingredient comprises one or more of ammonium bicarbonate, sodium bicarbonate, hexamethylenediamine, triethylamine, and ethanolamine.

2. The corrosion inhibitor according to claim 1, characterized in that, The adhesive is a mixture of sodium carboxymethyl cellulose, glycerin, polyethylene glycol and water; and / or the active ingredient is a mixture of ammonium bicarbonate and hexamethylenediamine.

3. The corrosion inhibitor according to claim 1 or 2, characterized in that, The molecular weight of polyethylene glycol is 300-3000, preferably 500-2500; and / or the viscosity of silicone oil is 100-500 mPa·s, preferably 300-500 mPa·s.

4. The corrosion inhibitor according to claim 2, characterized in that, Based on the total mass of the polythionite corrosion inhibitor, the sodium carboxymethyl cellulose content is 0.2-2.5%, the glycerin content is 5-15%, the polyethylene glycol content is 10-25%, and the active ingredient content is 10-30%.

5. The method for preparing the corrosion inhibitor according to any one of claims 1-4, characterized in that, The process includes the following steps: dissolving sodium carboxymethyl cellulose in water, adding glycerin and polyethylene glycol, and then mixing it evenly with the aqueous solution of the active ingredient to obtain a polythionic acid corrosion inhibitor.

6. The application of the corrosion inhibitor according to any one of claims 1-4 in sulfur-containing high-temperature equipment, characterized in that, Before storing high-temperature sulfur-containing equipment, the corrosion inhibitor is uniformly coated on the surface of the equipment.

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