Slow-release crude oil deferrization agent and preparation method thereof

Abstract

The invention discloses a slow-release crude oil deferrization agent and a preparation method thereof, and relates to the technical field of petrochemical engineering, the deferrization agent is formed by compounding an acidic biological complexing agent, a slow-release complexing agent, an acidic surfactant and a precipitator according to a specific proportion; the preparation method comprises the steps of respective preparation and final compounding of the components, iron ions in crude oil are rapidly captured through the acidic biological complexing agent, long-acting deep iron removal is achieved through the slow-release complexing agent, dispersity is improved through the acidic surfactant, sedimentation of an iron complex is promoted through the precipitator, and all the components have a synergistic effect. The deferrization agent is high in deferrization rate, good in slow release effect, qualified in stability and low in corrosion to equipment, can effectively reduce the iron content of crude oil, is suitable for an industrial electro-desalting process, and solves the problems that an existing deferrization agent is not thorough in deferrization, poor in slow release property and high in corrosion.

Description

Technical Field

[0001] This invention relates to the field of petrochemical technology, and in particular to a slow-release crude oil deferrochemical agent and its preparation method. Background Technology

[0002] Iron ions in crude oil mainly originate from equipment corrosion during extraction, introduction of formation water, and rust in oil pipelines. These iron ions exist in the form of inorganic salts and organic iron compounds. During crude oil processing, iron ions catalyze the oxidation of sulfides in the crude oil, leading to scaling and corrosion of equipment. They also affect the activity and lifespan of catalysts in subsequent processes such as catalytic cracking and hydrorefining, reducing product quality. Therefore, developing efficient crude oil iron removal agents is of great significance to the petroleum refining industry.

[0003] Currently, commercially available crude oil iron removal agents mainly consist of strong acids, complexing agents, and precipitants. Their working principle primarily involves disrupting the acid-base balance of the crude oil, using complexing agents to complex iron salts, and then combining this with precipitation and electrostatic desalting to remove iron ions. However, these iron removal agents have significant limitations: when the iron concentration in the crude oil is high, the iron removal speed is fast and efficient; but when the iron concentration is below 10 μg / g, the iron removal speed slows down significantly, and the efficiency and precision decrease drastically, failing to meet the requirements for deep iron removal from crude oil.

[0004] Furthermore, existing iron removal agents suffer from poor stability and short shelf life, and most contain strongly acidic components, which can cause severe corrosion to refining equipment with long-term use. Simultaneously, existing iron removal agents are extremely ineffective at removing oil-soluble iron, especially the insoluble iron compounds formed by the combination of iron with calcium and magnesium ions under neutral or alkaline conditions. To address these issues, some iron removal agents attempt to improve iron removal efficiency through composite complexing agents, but they fail to consider the slow-release properties of the complexing agents, resulting in a concentrated release of complexing capacity and an inability to achieve continuous iron removal. Other iron removal agents focus on combining solidification and iron removal, but their iron removal precision is insufficient, and they do not offer effective solutions to the difficulty in removing oil-soluble iron, thus failing to meet the needs of deep iron removal in industrial production.

[0005] For example, patent document CN107384471B discloses a phosphorus-free crude oil metal removal agent, which is a uniform, transparent solution with a solid content of 20-40% prepared by mixing an organic complex with deionized water at room temperature. The organic complex is prepared by mixing the following components in the following mass ratio at room temperature: chelating agent accounting for 30-50% of the total mass of the organic complex, organic acid 5-20%, carbonate 3-20%, and organic amine 7-27%. The chelating agent is a terpolymer of sodium styrene sulfonate, acrylamide, and hydroxypropyl acrylate. This phosphorus-free crude oil metal removal agent can be used to remove metals such as nickel, vanadium, and iron from crude oil and wastewater, with low dosage and high removal efficiency. However, it lacks a slow-release system, resulting in concentrated release of complexing ability, making it unable to achieve continuous iron removal when the iron concentration of crude oil fluctuates. Furthermore, its removal effect on oil-soluble iron is limited, and its insufficient stability leads to a short shelf life, making it difficult to meet the actual needs of deep iron removal in industrial production. Summary of the Invention

[0006] In view of the above, the present invention aims to provide a slow-release crude oil deferroagent and its preparation method. By optimizing the formula, it can achieve continuous and efficient deferroagent when the iron concentration of crude oil fluctuates, improve the deferroagent accuracy, improve the stability of the deferroagent, extend the shelf life, and reduce equipment corrosion.

[0007] To achieve the above objectives, the technical solution adopted in this invention is: a slow-release crude oil iron removal agent, which is compounded from an acidic biological complexing agent, a slow-release complexing agent, an acidic surfactant, and a precipitant in a volume ratio of (20-40):(35-55):(5-15):(8-12); the preparation process of each component is as follows: (1) Acidic biological complexing agent: Based on deionized water, citric acid and sodium alginate, 0.5-1.0 g / L of ascorbic acid is added, along with Span-80 and diatomaceous earth; (2) Slow-release complexing agent: Sodium polyacrylate, tetrasodium ethylenediaminetetraacetate, benzenesulfonic acid, urea, diethyl oxalate, ethanol with a mass percentage concentration of 95%, and ethyl silicate are used as the basic raw materials, and modified montmorillonite is added, along with hydroxypropyl methylcellulose and guar gum. (3) Acidic surfactant solution: Deionized water, ethanol with a mass percentage concentration of 95%, acetic acid, and polyether modified silicone oil are used as the base raw materials, with sodium dodecylbenzene sulfonate added and hexamethylenetetramine added at the same time; (4) Precipitator: Deionized water and anionic polyacrylamide are used as the base materials, and polyaluminum chloride is added.

[0008] Preferably, the average particle size of the diatomaceous earth is 100-300 mesh.

[0009] Preferably, the sodium polyacrylate is graded NP-700.

[0010] Preferably, the modified montmorillonite is Fenghong DK2 polymer-grade organic clay.

[0011] Preferably, the number-average molecular weight of the hydroxypropyl methylcellulose is 90,000.

[0012] Preferably, the polyether-modified silicone oil is of type DY-ET204.

[0013] Preferably, the grade of the anionic polyacrylamide is FP3530S.

[0014] Preferably, the product number of the polyaluminum chloride is WH15928.

[0015] Another object of the present invention is to provide a method for preparing the aforementioned slow-release crude oil iron removal agent, comprising the following steps: Step S1, Preparation of acidic biological complexing agent: Take 900-1100 mL of deionized water, add 52-56 g of citric acid, stir to dissolve at a stirring speed of 28-32 rpm for 10-15 min to obtain solution 1; add 0.5-1.0 g of ascorbic acid to solution 1 and stir until completely dissolved; add 3-6 g of... Mix Span-80 and 4-8g of diatomaceous earth thoroughly, maintaining a stirring speed of 28-32 rpm for 10-15 minutes. Take 105-109g of sodium alginate and heat the above solution 1 containing ascorbic acid, Span-80, and diatomaceous earth to 78-82℃, keeping the temperature stable and maintaining a stirring speed of 30-40 rpm. Slowly pour the sodium alginate into solution 1, continue heating and stirring for 28-32 minutes, stop heating and let stand for 10-15 minutes. Filter using medium-speed filter paper to remove insoluble impurities, and obtain the acidic biological complexing agent. Seal and store for later use. Step S2, Preparation of the sustained-release complexing agent solution: Take 55.2-58.2g of sodium polyacrylate, 84.2-86.2g of tetrasodium ethylenediaminetetraacetate, and 20-20.6g of benzenesulfonic acid. Mix the three solid powders thoroughly and grind them in a grinder. After grinding, pass the mixture through an 80-120 mesh sieve to obtain a mixed powder. Add 5-8g of modified montmorillonite, 14-16g of urea, and 19-21mL of diethyl oxalate to the mixed powder. Simultaneously add 3-6g of hydroxypropyl methylcellulose and 1.5-3g of guar gum. Stir well and place the mixture into a reaction vessel. Add 680-720mL of the solution to the reaction vessel. 95% ethanol, 290-310 mL of ethyl silicate, seal the reaction vessel, turn on the stirring device, stir at a speed of 40-45 rpm, heat to 73-78℃, and react at a constant temperature for 5-7 hours. After the reaction is completed, cool naturally to room temperature to obtain a slow-release complexing agent solution, which is then sealed and stored for later use. Step S3: Preparation of acidic surfactant solution: Take 740-760 mL of deionized water, add 240-260 mL of 95% ethanol, mix well, then add 290-310 g of acetic acid, stir to dissolve at a speed of 30-35 rpm for 14-16 min to obtain solution 3; add 3-5 g of sodium dodecylbenzenesulfonate and 1-2 g of hexamethylenetetramine to solution 3, and stir until completely dissolved; place solution 3 containing sodium dodecylbenzenesulfonate and hexamethylenetetramine in a refrigerator at 9-11℃ for 30-35 min, then slowly pour in 148-152 g of polyether modified silicone oil, stir thoroughly for 10-15 min at a speed of 50-55 rpm to obtain acidic surfactant solution, and seal and store for later use; Step S4, Preparation of precipitant: Take 900-1100 mL of deionized water, add 2.8-3.2 g of anionic polyacrylamide, heat to 38-42℃, stir at 20-25 rpm for 58-62 min until the anionic polyacrylamide is completely dissolved; add 5-10 g of polyaluminum chloride to the above solution, continue stirring for 20-25 min while maintaining the stirring speed at 20-25 rpm, and allow to cool naturally to room temperature to obtain the precipitant, which should be sealed and stored for later use. Step S5, Iron removal agent compounding: Measure the acidic biological complexing agent, slow-release complexing agent solution, acidic surfactant solution, and precipitant according to the volume ratio and put them into a stirred tank; heat the material in the stirred tank to 38-42℃, adjust the stirring speed to 60-65 rpm, and continue stirring for 14-16 minutes. After stirring, let it stand and cool naturally to room temperature to obtain the slow-release crude oil iron removal agent; put the prepared iron removal agent into a sealed container and store it in a cool and dry place.

[0016] Due to the application of the above technical solution, the present invention has the following beneficial effects: (1) The slow-release crude oil de-ironizing agent and its preparation method disclosed in this invention achieve synergistic effect of the four components by compounding acidic biological complexing agent, slow-release complexing agent, acidic surfactant and precipitant in a specific ratio and preparing each component precisely. Compared with existing crude oil de-ironizing agents, it produces unexpected de-ironization effect and application advantages, and completely solves the technical pain points of the existing technology such as incomplete de-ironization, low de-ironization efficiency, fast consumption of reagents and easy generation of secondary pollution. The acidic biological complexing agent, composed of citric acid, sodium alginate, ascorbic acid, Span-80, and diatomaceous earth, forms a synergistic system that can rapidly complex free iron ions in crude oil. The porous structure of diatomaceous earth can also adsorb the complexing products, while ascorbic acid can prevent secondary oxidation of iron ions. The slow-release complexing agent, composed of sodium polyacrylate, tetrasodium EDTA, modified montmorillonite, hydroxypropyl methylcellulose, and other components, achieves a long-term slow-release of the complexing effect, breaking the limitation of existing iron removal agents that are "instantaneous complexing and rapid failure". This extends the action period of the iron removal agent and reduces the frequency of agent addition.

[0017] (2) The slow-release crude oil de-ironizing agent and its preparation method disclosed in this invention significantly improve the de-ironizing efficiency and precision through the synergistic effect of each component, forming a complete de-ironizing system of "rapid complexation - long-term slow release - high-efficiency precipitation - deep purification". Compared with single complexing agents or simple compound de-ironizing agents, the de-ironizing rate is significantly improved, and it can effectively remove bound iron (such as iron sulfides and iron oxides) that are difficult to complex in crude oil, solving the technical bottleneck of difficult removal of bound iron in the prior art. Among them, the polyether-modified silicone oil, sodium dodecylbenzene sulfonate and hexamethylenetetramine in the acidic surfactant solution work synergistically to not only reduce the interfacial tension between crude oil and de-ironizing agent and promote the uniform dispersion of de-ironizing agent in crude oil, but also inhibit the redissolution of complexing products. The anionic polyacrylamide and polyaluminum chloride in the precipitant work synergistically to quickly flocculate and precipitate complexing products, preventing complexed iron ions from re-entering the crude oil system, realizing a closed loop in the de-ironizing process and significantly improving the quality of crude oil purification.

[0018] (3) The slow-release crude oil deferroagent and its preparation method disclosed in this invention, through the synergistic combination of components and preparation process, unexpectedly achieve a dual improvement in agent stability and environmental friendliness. Compared with existing deferroagents, it effectively solves the problems of agent easy stratification, poor storage stability, and strong corrosivity. The acidic biological complexing agent is compounded with natural raw materials and mild additives, which reduces the corrosivity of the agent to equipment. The synergistic effect of hydroxypropyl methylcellulose, guar gum, and modified montmorillonite in the slow-release complexing agent improves the viscosity and stability of the deferroagent, extending the storage period to more than 6 months without stratification. At the same time, the dosage of each component has been precisely optimized, with no excess harmful components. The precipitated products are easy to separate and treat, and will not cause secondary pollution to the environment. This not only reduces the environmental protection cost of crude oil treatment, but also avoids the impact on crude oil quality caused by redundant components in existing deferroagents, achieving a synergistic improvement in deferroagent effect, usage cost, and environmental performance.

[0019] (4) The slow-release crude oil deferroagent and its preparation method disclosed in this invention, through the synergistic effect of the preparation process and component compounding, unexpectedly reduce the application cost of the deferroagent and improve its industrial applicability. The preparation process of each component does not require harsh conditions such as high temperature and high pressure, the operation is simple and energy consumption is low, and the synergistic effect of each component reduces the amount of a single component. Compared with existing deferroagents, the amount of reagent can be significantly reduced. At the same time, no additional auxiliary reagents are required in the deferroagent process, which simplifies the crude oil deferroagent process. This deferroagent is suitable for crude oils with different iron contents, especially high iron content and high viscosity crude oils. After deferroagent, the viscosity, acid value and other indicators of the crude oil meet the requirements of subsequent processing. It solves the problem of the narrow applicability of existing deferroagents and the poor deferroagent effect on high viscosity crude oils. It provides an efficient, long-lasting, environmentally friendly and economical technical solution for deep deferroagent of crude oil and has significant industrial application value. Detailed Implementation

[0020] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. Example 1

[0021] A slow-release crude oil deferroabilizing agent is formulated from 400 mL of acidic biological complexing agent, 350 mL of slow-release complexing agent, 150 mL of acidic surfactant, and 100 mL of precipitant.

[0022] The preparation method of the slow-release crude oil iron removal agent includes the following steps: Step S1: Preparation of acidic bio-complexing agent: Take 1000mL of deionized water, add 52g of citric acid, stir to dissolve at a speed of 28 rpm for 10 min to obtain solution 1; add 0.5g of ascorbic acid to solution 1 and stir until completely dissolved; add 3g of Span-80 and 4g of diatomaceous earth to the above solution, stir evenly, and maintain a stirring speed of 28 rpm for 10 min; take 105g of sodium alginate, heat the above solution 1 containing ascorbic acid, Span-80 and diatomaceous earth to 78℃, keep the temperature stable, maintain a stirring speed of 30 rpm, slowly pour sodium alginate into solution 1, continue heating and stirring for 28 min, stop heating and let stand for 10 min, filter with medium-speed filter paper to remove insoluble impurities, and obtain acidic bio-complexing agent, which is sealed and stored for later use; Step S2, Preparation of the sustained-release complexing agent solution: Take 55.2g of sodium polyacrylate, 84.2g of tetrasodium ethylenediaminetetraacetate, and 20g of benzenesulfonic acid. Mix the three solid powders thoroughly and grind them in a grinder. After grinding, pass the mixture through a 100-mesh sieve to obtain a mixed powder. Add 5g of modified montmorillonite, 15g of urea, and 20mL of diethyl oxalate to the mixed powder. At the same time, add 3g of hydroxypropyl methylcellulose and 1.5g of guar gum. Stir evenly and then put the mixture into a reaction vessel. Add 700mL of 95% ethanol and 300mL of ethyl silicate to the reaction vessel. Seal the reaction vessel, turn on the stirring device, and stir at a speed of 40 rpm. Heat to 75℃ and react at a constant temperature for 6 hours. After the reaction is completed, allow it to cool naturally to room temperature to obtain the sustained-release complexing agent solution. Seal and store for later use. Step S3, Preparation of acidic surfactant solution: Take 750 mL of deionized water, add 250 mL of 95% ethanol, mix well, add 300 g of acetic acid, stir to dissolve at 33 rpm for 15 min to obtain solution 3; add 4 g of sodium dodecylbenzenesulfonate and 1.5 g of hexamethylenetetramine to solution 3, stir until completely dissolved; place solution 3 containing sodium dodecylbenzenesulfonate and hexamethylenetetramine in a 10°C refrigerator for 33 min, remove and slowly pour in 150 g of polyether modified silicone oil, stir thoroughly for 13 min at 50 rpm to obtain acidic surfactant solution, seal and store for later use; Step S4, Preparation of precipitant: Take 1000 mL of deionized water, add 3 g of anionic polyacrylamide, heat to 40 °C, stir at 20 rpm for 60 min until the anionic polyacrylamide is completely dissolved; add 5 g of polyaluminum chloride to the above solution, continue stirring for 20 min at 20 rpm, and allow to cool naturally to room temperature to obtain the precipitant, which should be sealed and stored for later use. Step S5, Iron removal agent compounding: Measure the acidic biological complexing agent, slow-release complexing agent solution, acidic surfactant solution, and precipitant according to the volume ratio and put them into a stirring tank; heat the material in the stirring tank to 40℃, adjust the stirring speed to 60 rpm, and stir continuously for 15 minutes. After stirring, let it stand and cool naturally to room temperature to obtain the slow-release crude oil iron removal agent; put the prepared iron removal agent into a sealed container and store it in a cool and dry place.

[0023] The diatomaceous earth has an average particle size of 100 mesh; the sodium polyacrylate is grade NP-700; the modified montmorillonite is Fenghong DK2 polymer-grade organic clay; the hydroxypropyl methylcellulose has a number-average molecular weight of 90,000; the polyether-modified silicone oil is grade DY-ET204; the anionic polyacrylamide is grade FP3530S; and the polyaluminum chloride has a product number of WH15928. Example 2

[0024] A slow-release crude oil deferroafer agent is basically the same as that in Example 1, except that it is composed of 300 mL of acidic biological complexing agent, 450 mL of slow-release complexing agent, 150 mL of acidic surfactant, and 100 mL of precipitant. Example 3

[0025] A slow-release crude oil deferroafer agent is basically the same as that in Example 1, except that it is composed of 350 mL of acidic biological complexing agent, 500 mL of slow-release complexing agent, 50 mL of acidic surfactant, and 100 mL of precipitant. Example 4

[0026] A slow-release crude oil deferroafer agent is basically the same as that in Example 1, except that it is composed of 200 mL of acidic biological complexing agent, 550 mL of slow-release complexing agent, 150 mL of acidic surfactant, and 100 mL of precipitant.

[0027] Comparative Example 1 A slow-release crude oil deferroplatin agent is basically the same as in Example 2, except that an equal amount of hydroxypropyl methylcellulose is used instead of guar gum.

[0028] Comparative Example 2 A slow-release crude oil deferroplating agent is basically the same as that in Example 2, except that an equal amount of guar gum is used instead of hydroxypropyl methylcellulose.

[0029] Comparative Example 3 A slow-release crude oil deferroplating agent is basically the same as in Example 2, except that urotropine is not added.

[0030] Comparative Example 4 A slow-release crude oil deferroplating agent is basically the same as that in Example 2, except that an equal amount of acidic biological complexing agent is used instead of the slow-release complexing agent.

[0031] Comparative Example 5 A slow-release crude oil deferroplating agent is basically the same as that in Example 2, except that an equal amount of slow-release complexing agent is used instead of the acidic biological complexing agent.

[0032] The slow-release crude oil iron removal agents of Example 2 and Comparative Examples 1-5 were subjected to relevant performance tests using the following experimental methods. The test results are shown in Table 1: (1) Iron removal effect test: An electro-desalting instrument was used to simulate the industrial electro-desalting process. The experimental parameters were set according to the actual industrial settings: temperature 125℃, water injection 5% / level, strong electric field strength 750V / cm, weak electric field strength 400V / cm, and settling time 10-30min. 120μg / g of iron removal agent was injected into the crude oil samples. Samples were taken at different settling time points (10min, 15min, 20min, 30min), and the iron content in the crude oil was determined by atomic absorption spectrophotometer. The iron removal rate was calculated as follows: iron removal rate = (initial iron content of crude oil - minimum iron content after iron removal) / initial iron content of crude oil × 100%. The iron content of the crude oil in each test was 26.4μg / g. (2) Stability test: Each product was placed in a sealed container and stored in a constant temperature and humidity storage box (temperature 25℃, humidity 60%). Samples were taken after 12 months of storage and the appearance of the iron removal agent was observed (whether it was layered or cloudy). If no layering or cloudiness was observed, the stability was qualified; otherwise, it was unqualified.

[0033] (3) Corrosion test: A corrosion tester was used and the test was performed in accordance with the national standard GB / T 10124-2021 "Metallic Materials Laboratory Uniform Corrosion Full Immersion Test Method". Carbon steel test pieces (material Q235) were immersed in the iron removal agent of each sample at a temperature of 40℃ for 72h. The corrosion rate of the test pieces was measured. Corrosion rate = (mass of test piece before immersion - mass of test piece after immersion) / (surface area of ​​test piece × immersion time), unit: mm / a.

[0034] Table 1. Performance test results of slow-release crude oil iron remover As can be seen from the data in Table 1, the slow-release crude oil deferrometallurgical agent described in this embodiment of the invention has a higher deferrometallurgical rate and efficiency, lower corrosiveness, and better slow-release effect (it can continuously release complexing active ingredients to achieve "gradual deferrometallurgy and continuous enhancement" rather than rapid failure after instantaneous complexation) compared with the comparative product, and also has good stability. The combined use of guar gum, hydroxypropyl methylcellulose, hexamethylenetetramine, slow-release complexing agent and acidic biological complexing agent has a positive promoting effect on improving the above-mentioned performance.

[0035] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A slow-release crude oil iron removal agent, characterized in that it is compounded from an acidic biological complexing agent, a slow-release complexing agent, an acidic surfactant, and a precipitant in a volume ratio of (20-40):(35-55):(5-15):(8-12); the preparation process of each component is as follows: (1) Acidic biological complexing agent: Based on deionized water, citric acid and sodium alginate, 0.5-1.0 g / L of ascorbic acid is added, along with Span-80 and diatomaceous earth; (2) Slow-release complexing agent: Sodium polyacrylate, tetrasodium ethylenediaminetetraacetate, benzenesulfonic acid, urea, diethyl oxalate, ethanol with a mass percentage concentration of 95%, and ethyl silicate are used as the basic raw materials, and modified montmorillonite is added, along with hydroxypropyl methylcellulose and guar gum. (3) Acidic surfactant solution: Deionized water, ethanol with a mass percentage concentration of 95%, acetic acid, and polyether modified silicone oil are used as the base raw materials, with sodium dodecylbenzene sulfonate added and hexamethylenetetramine added at the same time; (4) Precipitator: Deionized water and anionic polyacrylamide are used as the base raw materials, and polyaluminum chloride is added.

2. The slow-release crude oil deferroplatin agent according to claim 1, characterized in that, The average particle size of the diatomite is 100-300 mesh.

3. The slow-release crude oil deferroplatin agent according to claim 1, characterized in that, The sodium polyacrylate is designated as NP-700.

4. The slow-release crude oil deferroplating agent according to claim 1, characterized in that, The modified montmorillonite is Fenghong DK2 polymer-grade organic clay.

5. The slow-release crude oil deferroplatin agent according to claim 1, characterized in that, The number-average molecular weight of the hydroxypropyl methylcellulose is 90,000.

6. The slow-release crude oil deferroplatin agent according to claim 1, characterized in that, The polyether-modified silicone oil is designated as DY-ET204.

7. The slow-release crude oil deferroplatin agent according to claim 1, characterized in that, The grade of the anionic polyacrylamide is FP3530S.

8. The slow-release crude oil deferroplatin agent according to claim 1, characterized in that, The product number of the polyaluminum chloride is WH15928.

9. A method for preparing a slow-release crude oil deferroplating agent according to any one of claims 1-8, characterized in that, Includes the following steps: Step S1, Preparation of acidic biological complexing agent: Take 900-1100 mL of deionized water, add 52-56 g of citric acid, stir to dissolve at a stirring speed of 28-32 rpm for 10-15 min to obtain solution 1; add 0.5-1.0 g of ascorbic acid to solution 1 and stir until completely dissolved; add 3-6 g of... Mix Span-80 and 4-8g of diatomaceous earth thoroughly, maintaining a stirring speed of 28-32 rpm for 10-15 minutes. Take 105-109g of sodium alginate and heat the above solution 1 containing ascorbic acid, Span-80, and diatomaceous earth to 78-82℃, keeping the temperature stable and maintaining a stirring speed of 30-40 rpm. Slowly pour the sodium alginate into solution 1, continue heating and stirring for 28-32 minutes, stop heating and let stand for 10-15 minutes. Filter using medium-speed filter paper to remove insoluble impurities, and obtain the acidic biological complexing agent. Seal and store for later use. Step S2, Preparation of the sustained-release complexing agent solution: Take 55.2-58.2g of sodium polyacrylate, 84.2-86.2g of tetrasodium ethylenediaminetetraacetate, and 20-20.6g of benzenesulfonic acid. Mix the three solid powders thoroughly and grind them in a grinder. After grinding, pass the mixture through an 80-120 mesh sieve to obtain a mixed powder. Add 5-8g of modified montmorillonite, 14-16g of urea, and 19-21mL of diethyl oxalate to the mixed powder. Simultaneously add 3-6g of hydroxypropyl methylcellulose and 1.5-3g of guar gum. Stir well and place the mixture into a reaction vessel. Add 680-720mL of the solution to the reaction vessel. 95% ethanol, 290-310 mL of ethyl silicate, seal the reaction vessel, turn on the stirring device, stir at a speed of 40-45 rpm, heat to 73-78℃, and react at a constant temperature for 5-7 hours. After the reaction is completed, cool naturally to room temperature to obtain a slow-release complexing agent solution, which is then sealed and stored for later use. Step S3: Preparation of acidic surfactant solution: Take 740-760 mL of deionized water, add 240-260 mL of 95% ethanol, mix well, then add 290-310 g of acetic acid, stir to dissolve at a speed of 30-35 rpm for 14-16 min to obtain solution 3; add 3-5 g of sodium dodecylbenzenesulfonate and 1-2 g of hexamethylenetetramine to solution 3, and stir until completely dissolved; place solution 3 containing sodium dodecylbenzenesulfonate and hexamethylenetetramine in a refrigerator at 9-11℃ for 30-35 min, then slowly pour in 148-152 g of polyether modified silicone oil, stir thoroughly for 10-15 min at a speed of 50-55 rpm to obtain acidic surfactant solution, and seal and store for later use; Step S4, Preparation of precipitant: Take 900-1100 mL of deionized water, add 2.8-3.2 g of anionic polyacrylamide, heat to 38-42℃, stir at 20-25 rpm for 58-62 min until the anionic polyacrylamide is completely dissolved; add 5-10 g of polyaluminum chloride to the above solution, continue stirring for 20-25 min while maintaining the stirring speed at 20-25 rpm, and allow to cool naturally to room temperature to obtain the precipitant, which should be sealed and stored for later use. Step S5, Iron removal agent compounding: Measure the acidic biological complexing agent, slow-release complexing agent solution, acidic surfactant solution, and precipitant according to the volume ratio and put them into a stirred tank; heat the material in the stirred tank to 38-42℃, adjust the stirring speed to 60-65 rpm, and continue stirring for 14-16 minutes. After stirring, let it stand and cool naturally to room temperature to obtain the slow-release crude oil iron removal agent; put the prepared iron removal agent into a sealed container and store it in a cool and dry place.

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