Crude oil demetallization agent for removing oil-soluble metal elements in crude oil as well as preparation method and application of crude oil demetallization agent

Abstract

The invention relates to the technical field of crude oil deep pretreatment and demetallization, in particular to a crude oil demetallization agent for removing oil-soluble metal elements in crude oil and a preparation method and application of the crude oil demetallization agent. The crude oil demetalization agent is prepared from a carboxylic acid compound, an alcohol amine compound, an amide compound, a corrosion inhibitor, a surfactant and a solvent. The corrosion inhibitor comprises the following components in parts by weight: 5-50 parts of carboxylic acid compound, 1-30 parts of alcohol amine compound, 3-25 parts of amide compound, 0.05-5 parts of corrosion inhibitor, 0.1-2 parts of surfactant and 10-90 parts of solvent. The product provided by the invention has remarkable environmental protection advantage and low corrosivity, and the lowest freezing point of the product can reach-30 DEG C. The crude oil demetallization agent adopted by the invention can efficiently remove various oil-soluble metal element impurities in crude oil at the same time, the metal element removal rate can reach 99%, and the content index requirements of the oil refining industry on the metal element impurities in the crude oil can be completely met.

Description

Technical Field

[0001] This invention relates to the field of crude oil deep pretreatment demetallization technology, specifically to a crude oil demetallizing agent for removing oil-soluble metal elements from crude oil, its preparation method, and its application. Background Technology

[0002] Existing research results indicate that up to 45 metallic elements have been detected in crude oil. Although the content of metallic elements in crude oil is usually below 100 μg / g, the content of metallic elements in some heavy or low-quality crude oils may significantly exceed this range. For example, the V content in Venezuelan 380 crude oil is 154.71 μg / g, the total content of seven metallic elements (Ca, Ni, Fe, Na, Mn, V, and Cu) in Liaohe extra-heavy crude oil reaches 584.93 μg / g, and the calcium content in Sudanese crude oil is as high as 1200 μg / g, with some individual crude oils even reaching 1900 μg / g.

[0003] Different types of metal elements exist in crude oil in different states. Existing literature indicates that the existence of metal elements in crude oil can be divided into two categories: one is water-soluble metal elements existing in the form of water-soluble inorganic salts; the other is oil-soluble organometallic compounds, such as carboxylates, naphthenates, and macromolecular organometallic complexes of porphyrins or porphyrins. Water-soluble metal elements exist in the form of chlorides, carbonates, and sulfates; while oil-soluble metal elements mostly exist in the form of naphthenates, fatty acid salts, and phenolates. Calcium, magnesium, and iron, existing in the form of petroleum esters, account for a relatively high proportion, typically ranging from 30% to 85%. Sodium, nickel, and vanadium, existing in the form of petroleum esters, account for a relatively low proportion, generally not exceeding 10% of the total amount of the corresponding metal elements in crude oil. The metalloporphyrin compounds analyzed from crude oil include three types: primary porphyrin, deoxy-yew red primary porphyrin, and rose red porphyrin. Porphyrins are conjugated macrocyclic structures formed by four pyrrole rings linked by carbon chains. When the hydrogen atoms on the pyrrole nitrogen atoms in the porphyrin ring are replaced by metal ions, metalloporphyrin complexes are formed.

[0004] Metallic impurities in crude oil pose numerous hazards to the refining process: In atmospheric and vacuum distillation, metal salts precipitate and form scale deposits on the surfaces of heat exchangers and furnace tubes, reducing heat transfer efficiency and causing pipeline blockage and under-deposit corrosion; in catalytic cracking, metals such as iron, calcium, nickel, and vanadium can poison the catalyst, significantly reducing the yield and quality of light oil products; in heavy oil hydrotreating, metal components react with H2S to form metal sulfides, causing gradual deactivation of catalyst active sites; in catalytic reforming, metals such as lead and copper can also cause permanent poisoning and deactivation of precious metal catalysts. Furthermore, metallic impurities can affect key quality indicators of products such as petroleum asphalt, for example, causing the elongation of asphalt prepared from vacuum residue to fail to meet standards. These hazards not only shorten the operating cycle of crude oil processing units but also seriously affect the added value of products and the economic benefits of refineries. Therefore, it is essential to employ efficient demetallization technology in the crude oil pretreatment stage to ensure the safe and stable operation of the entire crude oil processing process.

[0005] For a long time, refineries both domestically and internationally have widely adopted electro-desalting pretreatment technology to remove water-soluble inorganic salts from crude oil, thereby simultaneously removing water-soluble metal elements existing in the form of water-soluble inorganic salts. This process is based on a high-voltage electric field synergistic with thermochemical demulsification. In crude oil with the injection of a certain amount of water and demulsifier, the oil-water emulsion demulsifies and the oil-water phase separates, ultimately removing metal elements existing in the form of water-soluble inorganic salts through oil-water separation. While electro-desalting pretreatment technology can remove most water-soluble metal elements existing in the form of water-soluble inorganic salts from crude oil, it is not effective in removing organometallic elements existing in the form of oil-soluble petroleum salts.

[0006] Comparative document 1CN 116536076 B, "Mixed Acid Decalcifying Agent and Method for Removing Calcium Content from Petrochemicals," relates to a mixed acid decalcifying agent and a method for removing calcium content from petrochemicals. The mixed acid decalcifying agent comprises a water-soluble organic acid, an additive, and polymaleic acid; the water-soluble organic acid is selected from one or more mixtures of acetic acid, glycolic acid, citric acid, oxalic acid, and lactic acid. Because it uses small-molecule organic acids such as acetic acid and glycolic acid, the decalcifying agent is strongly acidic. Although adding ammonia can adjust the pH of the solution to around 5.5, it will still cause severe corrosion to the electro-desalination unit and pipelines.

[0007] Prior art document 2CN1267707 discloses a method for decalcifying hydrocarbon oils, using aminosulfonic acid or sulfuric acid as a demetallizing agent and sodium chloride, ammonium chloride, or sodium nitrate and ammonium nitrate as excipients. Prior art document 3CN1657596A uses a mixture of chelating agents (carboxylic acids, polyphosphoric acid, organophosphonic acids, hydroxyquinoline, amino acids and their derivatives, etc.), precipitating agents (sulfuric acid, carbonic acid, silicic acid, etc.), phase transfer agents (quaternary ammonium salts, polyethylene glycol, etc.), and demulsifiers for demetallizing hydrocarbon oils, showing good removal efficiency for Ca. The demetallizing agents in the aforementioned comparative documents all contain chlorine (Cl), phosphorus (P), and sulfur (S). Using demetallizing agents containing these elements in crude oil deep pretreatment demetallization poses multiple hazards: First, chlorine readily forms hydrochloric acid (HCl) under high temperature or acidic conditions, which not only severely corrodes refining equipment but may also lead to catalyst poisoning. Second, sulfur may be converted into hydrogen sulfide (H2S), which not only exacerbates equipment corrosion and catalyst deactivation but also increases the sulfur content of crude oil products. Furthermore, phosphorus compounds entering the desalting water from electro-desalination processes can easily cause eutrophication, increasing the difficulty of treating phosphorus-containing wastewater. All of these factors will have serious negative impacts on the stable operation of the crude oil processing process and environmental protection.

[0008] In summary, conventional crude oil demetallizing agents suffer from the following technical problems: 1) They are mostly water-based formulations, which can lead to increased solution viscosity, reduced fluidity, precipitation of active ingredients, and even freezing under low-temperature conditions; they also cannot effectively remove oil-soluble organometallic compounds, such as carboxylates, naphthenates, and porphyrin or porphyrin-like macromolecular organometallic complexes. 2) They are mostly moderately to strongly acidic, causing severe corrosion to electro-desalting units and pipelines. 3) The sulfur present may be converted into hydrogen sulfide (H2S), which will not only exacerbate equipment corrosion and catalyst deactivation but also increase the sulfur content of crude oil products. 4) Phosphorus compounds entering the desalted water can easily cause eutrophication, increasing the difficulty of treating phosphorus-containing wastewater; all of these factors will have serious negative impacts on the stable operation of the crude oil processing process and environmental protection. Summary of the Invention

[0009] To overcome the deficiencies of the prior art described above, this invention provides a crude oil demetallizing agent for removing oil-soluble metal elements from crude oil.

[0010] Another objective of this invention is to provide a method for preparing a crude oil demetallizing agent for removing oil-soluble metal elements from crude oil.

[0011] Another object of the present invention is to provide an application of a crude oil demetallizing agent for removing oil-soluble metal elements from crude oil.

[0012] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0013] A crude oil demetallizing agent for removing oil-soluble metal elements from crude oil is prepared from carboxylic acid compounds, alkanolamine compounds, amide compounds, corrosion inhibitors, surfactants, and solvents; wherein, the carboxylic acid compounds are 5-50 parts by weight, the alkanolamine compounds are 1-30 parts by weight, the amide compounds are 3-25 parts by weight, the corrosion inhibitors are 0.05-5 parts by weight, the surfactants are 0.1-2 parts by weight, and the solvents are 10-90 parts by weight.

[0014] Preferably, the mass ratio of carboxylic acid compounds to amide compounds in the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil is 1:0.8 to 1.2.

[0015] Preferably, the mass ratio of carboxylic acid compounds to amide compounds in the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil is 1:0.9 to 1.1.

[0016] Preferably, the mass ratio of carboxylic acid compounds to amide compounds in the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil is 1:1.

[0017] Preferably, the carboxylic acid compound comprises any one or more monocarboxylic acids or polycarboxylic acids.

[0018] More preferably, the carboxylic acid compound is lactic acid, adipic acid, benzoic acid, succinic acid, or phenylpropionic acid.

[0019] More preferably, the carboxylic acid compound is adipic acid.

[0020] Preferably, the alkanolamine compound comprises any one or more of ethanolamine (monoethanolamine), propanolamine, diethanolamine, diisopropanolamine, triethanolamine, and butanolamine.

[0021] More preferably, the alcoholamine compound is propanolamine.

[0022] Preferably, the amide compound comprises any one or more of aliphatic monoamides and aromatic monoamides.

[0023] Preferably, the amide compound comprises any one or more of formamide, acetamide, propionamide, and benzamide.

[0024] More preferably, the amide compound is formamide or acetamide.

[0025] Preferably, the corrosion inhibitor comprises any one or more of amino acid compounds, aniline aldehyde condensates, and imidazole compounds.

[0026] More preferably, the corrosion inhibitor is asparagine, asparagine polymer, dimethylimidazole, trimethylimidazole, or aniline formaldehyde polymer.

[0027] More preferably, the corrosion inhibitor is asparagine.

[0028] Preferably, the surfactant comprises one or more of nonionic surfactants and cationic surfactants.

[0029] More preferably, the surfactant is nonylphenol polyoxyethylene ether, alkyl alcohol polyoxyethylene ether, or EO / PO grafted polyoxyethylene ether.

[0030] More preferably, the surfactant is nonylphenol polyoxyethylene ether.

[0031] Preferably, the solvent is an alcohol;

[0032] Preferably, the solvent is any one or more of methanol, ethanol, ethylene glycol, n-propanol, and isopropanol.

[0033] More preferably, the solvent is ethanol.

[0034] Preferably, the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil is prepared from the following components in parts by weight: 35-45 parts by weight of solvent, 1-2 parts by weight of surfactant, 3-4 parts by weight of corrosion inhibitor, 18-22 parts by weight of amide compound, 18-22 parts by weight of carboxylic acid compound, and 10-20 parts by weight of alkanolamine compound.

[0035] In this invention, when the solvent, surfactant, corrosion inhibitor, amide compound, carboxylic acid compound, and alkanolamine compound in the crude oil demetallizer for removing oil-soluble metal elements meet the above proportions, the metal element removal performance, antifreeze performance, and environmental performance of the crude oil demetallizer are better.

[0036] Preferably, the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil is prepared from the following components in parts by weight: 35-45 parts by weight of ethanol, 1-2 parts by weight of nonylphenol polyoxyethylene ether, 3-4 parts by weight of dimethylimidazole, 18-22 parts by weight of acetamide, 18-22 parts by weight of lactic acid, and 10-20 parts by weight of monoethanolamine.

[0037] Preferably, the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil is prepared from the following components in parts by weight: 35-45 parts by weight of methanol, 1-2 parts by weight of nonylphenol polyoxyethylene ether, 3-4 parts by weight of asparagine, 18-22 parts by weight of formamide, 18-22 parts by weight of adipic acid, and 10-20 parts by weight of propanolamine.

[0038] Preferably, the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil is prepared from the following components in parts by weight: 35-45 parts by weight of ethylene glycol, 1-2 parts by weight of alkyl alcohol polyoxyethylene ether, 3-4 parts by weight of aniline formaldehyde polymer, 18-22 parts by weight of acetamide, 18-22 parts by weight of benzoic acid, and 10-20 parts by weight of diethanolamine.

[0039] Preferably, the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil is prepared from the following components in parts by weight: 35-45 parts by weight of methanol, 1-2 parts by weight of EO / PO grafted polyoxyethylene ether, 3-4 parts by weight of asparagine polymer, 18-22 parts by weight of acetamide, 18-22 parts by weight of benzoic acid, and 10-20 parts by weight of diisopropanolamine.

[0040] Preferably, the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil is prepared from the following components in parts by weight: 35-45 parts by weight of ethylene glycol, 1-2 parts by weight of nonylphenol polyoxyethylene ether, 3-4 parts by weight of dimethylimidazole, 18-22 parts by weight of acetamide, 18-22 parts by weight of succinic acid, and 10-20 parts by weight of monoethanolamine.

[0041] Preferably, the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil is prepared from the following components in parts by weight: 35-45 parts by weight of isopropanol, 1-2 parts by weight of nonylphenol polyoxyethylene ether, 3-4 parts by weight of trimethylimidazole, 18-22 parts by weight of acetamide, 18-22 parts by weight of phenylpropionic acid, and 10-20 parts by weight of triethanolamine.

[0042] More preferably, the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil is prepared from the following components in parts by weight: 35-45 parts by weight of ethanol, 1-2 parts by weight of nonylphenol polyoxyethylene ether, 2-4 parts by weight of asparagine, 18-22 parts by weight of acetamide, 18-22 parts by weight of adipic acid, and 13-17 parts by weight of propanolamine.

[0043] Furthermore, the preparation method of the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil includes the following steps:

[0044] The solvent is preheated, and under normal pressure and stirring speed of 50-300 rpm, carboxylic acid compounds, alkanolamine compounds, amide compounds, corrosion inhibitors and surfactants are added according to the weight ratio of the formula. By stirring, the components are mixed and reacted until a homogeneous solution is formed, thus preparing the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil.

[0045] In this invention, carboxylic acid compounds react with alcohol amine compounds to generate new compounds and reduce the acidity of the carboxylic acid mixture.

[0046] Preferably, the solvent preheating temperature is 20–50°C.

[0047] Preferably, the mixing reaction time in the preparation method of the crude oil demetallizing agent is 0.5 to 2.0 hours.

[0048] Preferably, the mixing reaction time in the preparation method of the crude oil demetallizing agent is 0.5 to 1.0 hours.

[0049] Preferably, the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil has a pH value of 5.0 to 6.0 and a freezing point of -30°C, as determined by GB / T 510-2018 "Determination of Pour Point of Petroleum Products".

[0050] Application of a crude oil demetallizing agent for removing oil-soluble metal elements from crude oil, used for deep pretreatment demetallization of crude oil.

[0051] Furthermore, the crude oil deep pretreatment demetallization method includes the following steps:

[0052] S1. Preheat the crude oil, then add crude oil demetallizing agent (to remove oil-soluble metal elements from the crude oil), water and demulsifier, mix thoroughly and react to obtain an oil-water emulsion;

[0053] S2. The oil-water emulsion obtained in step S1 is injected into an electro-desalting device for conventional electro-desalting and demetallization treatment to obtain crude oil with metal elements removed.

[0054] The electro-desalination device includes a primary electro-desalination tank and a secondary electro-desalination tank.

[0055] Preferably, the crude oil preheating temperature in step S1 is 100–165°C.

[0056] More preferably, the crude oil preheating temperature in step S1 is 100-155°C.

[0057] Preferably, the amount of water used in step S1 is 3 to 7 wt.% (meaning 3 to 7 grams of water are added to every 100 grams of crude oil).

[0058] Preferably, the amount of crude oil demetallizing agent used in step S1 is 50-1500 μg / g (meaning 50-1500 micrograms of demetallizing agent are added per gram of crude oil).

[0059] More preferably, the crude oil density in step S1 is less than 0.95 g / cm³. 3 At that time, the amount of the crude oil demetallizing agent used was 50-300 μg / g.

[0060] More preferably, the crude oil density in step S1 is greater than 0.95 g / cm³. 3At that time, the amount of the crude oil demetallizing agent used was 800-1500 μg / g.

[0061] Preferably, the demulsifier in step S1 comprises an oil-soluble demulsifier or a water-soluble demulsifier.

[0062] Preferably, the demulsifier in step S1 includes HG-952 type water-soluble demulsifier.

[0063] Preferably, the amount of demulsifier used in step S1 is 10-50 μg / g (meaning 10-50 micrograms of demulsifier are added per gram of crude oil).

[0064] Preferably, the thorough mixing in step S1 includes using a static mixer and / or a mixing valve.

[0065] In this invention, crude oil is preheated and then mixed with crude oil demetallizing agent, water and demulsifier to obtain an oil-water emulsion, which facilitates the transfer of oil-soluble metal elements in crude oil to the aqueous phase.

[0066] Preferably, the operating pressure of the electro-desalination tank in step S2 is 0.4 to 0.9 MPa.

[0067] Preferably, the operating conditions of the electro-desalination device in step S2 are as follows: the inlet temperature of the primary electro-desalination tank is 100-160°C, the outlet temperature of the primary electro-desalination tank is 100-160°C, the inlet temperature of the secondary electro-desalination tank is 100-160°C, and the outlet temperature of the secondary electro-desalination tank is 100-150°C.

[0068] Preferably, after the electro-desalination device reaches stable operation again in step S2, the current of the first-stage electro-desalination tank drops to 120A, and the current of the second-stage electro-desalination tank drops to 90A.

[0069] In this invention, the oil-water emulsion is demulsified and dehydrated in an electro-desalting device through the synergistic effect of an electric field, a demulsifier, and temperature, and then separated into oil and water under gravity to obtain crude oil with metal elements removed.

[0070] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0071] This invention provides a crude oil demetallizing agent for removing oil-soluble metal elements from crude oil. Its formulation is free of harmful heteroatoms such as fluorine, chlorine, sulfur, and phosphorus, offering significant environmental advantages. The demetallizing agent of this invention has a pH value controlled within a weakly acidic range of 5-6, exhibiting low corrosivity to metal equipment and pipelines. The corrosion rate on 20# carbon steel at 50℃ is 0.0970 mm / a, with a corrosion grade of 5, classifying it as corrosion-resistant. It can be stored in ordinary carbon steel storage tanks, significantly reducing the investment in equipment modification and minimizing corrosion of existing equipment. Through innovative formulation design, the demetallizing agent of this invention possesses excellent low-temperature flow properties, with a freezing point significantly lower than existing commercial products, reaching -30℃, meeting the normal pumping requirements under the harsh winter conditions of northern my country.

[0072] The solvent system used in the demetallizing agent of this invention not only lowers the freezing point of the demetallizing agent but also significantly enhances its miscibility with crude oil. Simultaneously, through the synergistic effect of multiple effective components, it can efficiently remove various oil-soluble metal element impurities from crude oil. In practical applications, the removal rate of calcium and sodium elements can reach over 99%. The dosage of the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil depends on the content of metal elements in the crude oil and the depth of removal, and the dosage is generally in the range of 50–1500 μg / g.

[0073] The crude oil demetallizing agent of this invention can reduce the electric field current of the electrostatic desalting tank by 30-80A, effectively reducing the energy consumption of the electrostatic desalting unit. Laboratory studies and industrial-scale tests show that using this environmentally friendly, economical, and highly efficient crude oil demetallizing agent, after deep pretreatment to remove oil-soluble metal elements from crude oil, significantly reduces the viscosity and the content of major metal elements, and also lowers the density. This not only improves the storage and transportation performance of crude oil but also achieves partial upgrading and improves its quality, providing strong technical support for the processing and utilization of crude oil, especially heavy and low-quality crude oil resources. Detailed Implementation

[0074] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0075] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0076] The testing method used in this application is:

[0077] The content of metal elements in crude oil was determined according to GB / T 37160-2019 "Determination of trace metal elements in heavy distillate oil, residue oil and crude oil by inductively coupled plasma atomic emission spectrometry".

[0078] The dynamic viscosity of extra-heavy oil was determined according to SY / T 0520-2008 "Determination of Crude Oil Viscosity - Rotational Viscometer Equilibrium Method".

[0079] The ash content of petroleum coke products was determined according to SH / T 0029-1990 "Determination of Ash Content in Petroleum Coke".

[0080] The quality of petroleum coke was evaluated in accordance with SH / T 0527-2019 "Quality Indicators of Delayed Petroleum Coke".

[0081] Example 1

[0082] (1) A crude oil demetallizing agent for removing oil-soluble metal elements from crude oil, the specific preparation method of which is as follows:

[0083] Preheat 40g of ethanol to 40-45℃. Add 1g of nonylphenol polyoxyethylene ether surfactant, 3g of dimethylimidazolium corrosion inhibitor, 20g of acetamide, 21g of lactic acid, and 15g of monoethanolamine to a 250ml glass container. Stir for 30 minutes at 150rpm within the temperature range of 40-45℃ until the mixture is homogeneous and reacted to obtain the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil as described in this invention, named MPT01 type crude oil demetallizing agent.

[0084] (2) The crude oil deep pretreatment demetallization process consists of the following steps:

[0085] The density is 0.9283 g / cm³ 3Imported crude oil is preheated to 142℃, then 250μg / g of MPT01 crude oil demetallizing agent, 5wt.% softened water, and 50μg / g of HG-952 water-soluble demulsifier are added. After thorough mixing via a static mixer and mixing valve, an oil-water emulsion is obtained. This emulsion is injected into an electrostatic desalting unit where oil and water are separated under the synergistic effects of an electric field, demulsifier, temperature, and gravity to obtain crude oil with demetallic elements removed. The operating conditions of the electrostatic desalting unit are: desalting tank operating pressure 0.58~0.60MPa, first-stage electrostatic desalting tank inlet temperature 135~142℃, and first-stage electrostatic desalting... The salt tank outlet temperature is 133–141℃, the secondary electric desalting tank inlet temperature is 132–140℃, the secondary electric desalting tank outlet temperature is 132–137℃, the primary electric desalting tank current is 115–180A, the secondary electric desalting tank current is 90–130A, the primary electric desalting tank water injection rate is 4.5–6.0 t / h, the secondary electric desalting tank water injection rate is 3.7–5.0 t / h, the primary electric desalting tank static mixer and mixing valve differential pressure is 101.0–106.0 kPa, the secondary electric desalting tank static mixer and mixing valve differential pressure is 85.0–88 kPa, and the crude oil processing rate is 60–63 t / h. When MPT01 type crude oil demetallizing agent is added and the electric desalting unit operates stably, the electric field currents of the primary and secondary electric desalting tanks drop to approximately 120A and 90A, respectively.

[0086] The metal content of the crude oil was determined. After adding MPT01 crude oil demetallizing agent for deep metal pretreatment, the removal rates of calcium, sodium, iron, copper, and nickel in the crude oil were 99.1%, 94.6%, 82.9%, 44.4%, and 23.2%, achieving excellent demetallization results.

[0087] Example 2

[0088] (1) A crude oil demetallizing agent for removing oil-soluble metal elements from crude oil, the specific preparation method of which is as follows:

[0089] Preheat 40g of methanol to 40-45℃, then add 2g of nonylphenol polyoxyethylene ether surfactant, 3g of asparagine corrosion inhibitor, 20g of formamide, 20g of adipic acid, and 15g of propanolamine into a 250ml glass container. Stir for 40 minutes at 40-45℃ and a stirring speed of 200rpm to ensure that all components are mixed evenly. This yields the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil as described in this invention, named MTP02 type crude oil demetallizing agent.

[0090] (2) The crude oil deep pretreatment demetallization process consists of the following steps:

[0091] With a density of 0.9120 g / cm³ 3The crude oil transported via pipeline is preheated to 130℃, then 200μg / g of MPT02 crude oil demetallizing agent, 5wt.% softened water, and 20μg / g of HG-952 water-soluble demulsifier are added. After thorough mixing via a static mixer and mixing valve, an oil-water emulsion is obtained. This emulsion is injected into an electrostatic desalting unit where oil and water are separated under the synergistic effects of an electric field, demulsifier, temperature, and gravity to obtain crude oil with demetallic elements removed. The operating conditions of the electrostatic desalting unit are: desalting tank operating pressure 0.50~0.56MPa, and inlet temperature of the first-stage electrostatic desalting tank... The temperature ranges as follows: 130–135℃ for the primary electrostatic precipitator, 128–133℃ for the outlet of the primary electrostatic precipitator, 127–130℃ for the inlet of the secondary electrostatic precipitator, and 125–128℃ for the outlet of the secondary electrostatic precipitator. The water injection rate for the primary electrostatic precipitator is 31.0–32.0 t / h, and for the secondary electrostatic precipitator it is 30.0–31.5 t / h. The pressure difference between the static mixer and mixing valve in the primary electrostatic precipitator is 95.0–102.0 kPa, and for the secondary electrostatic precipitator it is 85.0–90.0 kPa. The crude oil processing capacity is 620–630 t / h. The metal element content of the obtained crude oil is determined. After adding MPT02 crude oil demetallizing agent for deep metal pretreatment, the removal rates of calcium, sodium, iron, aluminum, nickel, and vanadium in the crude oil were 93.2%, 94.7%, 55.5%, 78.6%, 8.0%, and 10.9%, respectively.

[0092] Example 3

[0093] (1) A crude oil demetallizing agent for removing oil-soluble metal elements from crude oil, the specific preparation method of which is as follows:

[0094] Preheat 45g of ethylene glycol to 45-50℃. Add 2g of alkyl alcohol polyoxyethylene ether surfactant, 3g of aniline formaldehyde polymer corrosion inhibitor, 20g of acetamide, 20g of benzoic acid, and 10g of diethanolamine to a 250ml glass container. Stir for 50 minutes at 45-50℃ and a stirring speed of 250rpm to obtain the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil as described in this invention, named MTP03 type crude oil demetallizing agent.

[0095] (2) The crude oil deep pretreatment demetallization process consists of the following steps:

[0096] With a density of 0.8362 g / cm³ 3The crude oil mixture of North China crude oil and imported Russian crude oil is preheated to 135℃, then 150μg / g of MPT03 crude oil demetallizing agent, 5wt.% purified water, and 50μg / g of HG-952 water-soluble demulsifier are added. After thorough mixing through a static mixer and mixing valve, an oil-water emulsion is obtained. The oil-water emulsion is injected into an electrostatic desalting unit where oil and water are separated under the synergistic effects of an electric field, demulsifier, temperature, and gravity to obtain crude oil with demetallic elements removed. The operating conditions of the electrostatic desalting unit are: desalting tank operating pressure 0.52~0.58MPa, first-stage electrostatic desalting tank inlet temperature 132~137℃, and first-stage electrostatic desalting tank outlet temperature 130~135℃. The inlet temperature of the secondary electrostatic desalting tank is 128–133℃, and the outlet temperature is 126–131℃. The water injection rate of the primary electrostatic desalting tank is 25.0–25.6 t / h, and that of the secondary electrostatic desalting tank is 24.5–25.0 t / h. The pressure difference between the static mixer and mixing valve in the primary electrostatic desalting tank is 93.0–98.0 kPa, and that of the static mixer and mixing valve in the secondary electrostatic desalting tank is 80.0–85.0 kPa. The crude oil processing capacity is 500–510 t / h. The metal element content of the obtained crude oil was determined. After deep metal pretreatment of the crude oil with MPT03 crude oil demetallizing agent, the removal rates of calcium, iron, sodium, nickel, and vanadium were 94.4%, 94.1%, 99.6%, 9.2%, and 5.0%, respectively, with a total removal rate of 66.7% for the five metal elements.

[0097] Example 4

[0098] (1) A crude oil demetallizing agent for removing oil-soluble metal elements from crude oil, the specific preparation method of which is as follows:

[0099] Preheat 35g of methanol to 40-45℃, add 2g of EO / PO grafted polyoxyethylene ether surfactant, 3g of asparagine polymer corrosion inhibitor, 20g of acetamide, 20g of benzoic acid, and 20g of diisopropanolamine to a 250ml glass container, and stir at 250rpm for 30min within the temperature range of 40-45℃ until homogeneous to obtain the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil as described in this invention, named MTP04 type crude oil demetallizing agent.

[0100] (2) The crude oil deep pretreatment demetallization process consists of the following steps:

[0101] With a density of 0.8551 g / cm³ 3The crude oil mixture of Golmud pipeline crude oil and Lenghu crude oil is preheated to 131℃, then 150μg / g of MPT04 crude oil demetallizing agent, 5wt.% purified water, and 50μg / g of HG-952 water-soluble demulsifier are added. After thorough mixing through a static mixer and mixing valve, an oil-water emulsion is obtained. This emulsion is injected into an electrostatic desalting unit where oil and water are separated under the synergistic effects of an electric field, demulsifier, temperature, and gravity to obtain crude oil with demetallic elements removed. The operating conditions of the electrostatic desalting unit are: desalting tank operating pressure 0.47~0.50MPa... The inlet temperature of the first-stage electrostatic desalting tank is 131–135℃, the outlet temperature is 129–133℃, the inlet temperature of the second-stage electrostatic desalting tank is 127–131℃, and the outlet temperature is 125–129℃. The water injection rate of the first-stage electrostatic desalting tank is 4.8–5.2 t / h, and the water injection rate of the second-stage electrostatic desalting tank is 4.5–5.0 t / h. The pressure difference between the static mixer and mixing valve in the first-stage electrostatic desalting tank is 45.0–48.0 kPa, and the pressure difference between the static mixer and mixing valve in the second-stage electrostatic desalting tank is 40.0–45.0 kPa. The crude oil processing capacity is 130–140 t / h. The metal element content of the obtained crude oil is determined. After adding MPT04 type crude oil demetallizing agent for deep metal pretreatment, the removal rates of calcium, iron, sodium, and nickel in the crude oil are 48.4%, 54.1%, 91.6%, and 35.0%, respectively.

[0102] Example 5

[0103] (1) A crude oil demetallizing agent for removing oil-soluble metal elements from crude oil, the specific preparation method of which is as follows:

[0104] Preheat 45g of ethylene glycol to 40-45℃. Add 1g of nonylphenol polyoxyethylene ether surfactant, 4g of dimethyl imidazole corrosion inhibitor, 20g of acetamide, 20g of succinic acid, and 10g of monoethanolamine to a 250ml glass container. Stir at 250rpm for 60 minutes within the temperature range of 40-45℃ until homogeneous to obtain the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil as described in this invention, named MTP05 type crude oil demetallizing agent.

[0105] (2) The crude oil deep pretreatment demetallization process consists of the following steps:

[0106] With a density of 0.8736 g / cm³ 3The crude oil mixture of Daqing pipeline crude oil and Jidong crude oil is preheated to 105–110℃, then 60 μg / g of MPT05 crude oil demetallizing agent, 3.5–4.5 wt.% purified water, and 50 μg / g of HG-952 water-soluble demulsifier are added. After thorough mixing via a static mixer and mixing valve, an oil-water emulsion is obtained. This emulsion is injected into an electrostatic desalting unit where oil and water are separated under the synergistic effects of an electric field, demulsifier, temperature, and gravity to obtain crude oil with demetallic elements removed. The operating conditions of the electrostatic desalting unit are: desalting tank operating pressure 0.7–0.8 MPa. The inlet temperature of the primary electrostatic desalting tank is 105–110℃, and the outlet temperature is 103–108℃. The inlet temperature of the secondary electrostatic desalting tank is 101–105℃, and the outlet temperature is 100–103℃. The water injection rate of the primary electrostatic desalting tank is 14.5–17.7 t / h, and that of the secondary electrostatic desalting tank is 14.0–17.0 t / h. The pressure difference between the static mixer and mixing valve in the primary electrostatic desalting tank is 50.0–78.0 kPa, and that of the secondary electrostatic desalting tank is 50.0–70.0 kPa. The crude oil processing capacity is 292–356 t / h. The metal element content of the obtained crude oil was determined. After pretreatment with MPT05 crude oil demetallizing agent, the removal rates of calcium, iron, sodium, and nickel were 82.2%, 54.4%, 100.0%, and 8.8%, respectively.

[0107] Example 6

[0108] (1) A crude oil demetallizing agent for removing oil-soluble metal elements from crude oil, the specific preparation method of which is as follows:

[0109] Preheat 40g of isopropanol to 40-45℃, then add 2g of nonylphenol polyoxyethylene ether surfactant, 3g of trimethylimidazolium corrosion inhibitor, 20g of acetamide, 20g of phenylpropionic acid, and 15g of triethanolamine to a 250ml glass container. Stir at 300rpm for 45 minutes within the temperature range of 40-45℃ until homogeneous to obtain the crude oil demetallizing agent for removing oil-soluble metal elements from crude oil as described in this invention, named MTP06 type crude oil demetallizing agent.

[0110] (2) The crude oil deep pretreatment demetallization process consists of the following steps:

[0111] With a density of 0.9983 g / cm³ 3The Liaohe extra-heavy crude oil is preheated to 145–155°C, then 1500 μg / g of MPT06 crude oil demetallizing agent, 6.0 wt.% purified water, and 50 μg / g of HG-952 water-soluble demulsifier are added. After thorough mixing via a static mixer and mixing valve, an oil-water emulsion is obtained. The oil-water emulsion is injected into an electrostatic desalting unit where oil and water are separated under the synergistic effects of an electric field, demulsifier, temperature, and gravity to obtain crude oil with demetallic elements removed. The operating conditions of the electrostatic desalting unit are: desalting tank operating pressure 0.7–0. The pressure is 8 MPa. The inlet temperature of the first-stage electric desalting tank is 145–155℃, and the outlet temperature is 143–153℃. The inlet temperature of the second-stage electric desalting tank is 141–150℃, and the outlet temperature is 140–148℃. The water injection rate of the first-stage electric desalting tank is 6.0 t / h, and the water injection rate of the second-stage electric desalting tank is 4.0 t / h. The pressure difference between the static mixer and mixing valve in the first-stage electric desalting tank is approximately 60.0 kPa, and the pressure difference between the static mixer and mixing valve in the second-stage electric desalting tank is approximately 50.0 kPa. The crude oil processing capacity is 100 t / h. The metal element content of the obtained crude oil is determined. After adding MPT06 crude oil demetallizing agent for deep metal pretreatment, the removal rates of calcium, iron, and manganese in the crude oil are 97.7%, 97.7%, and 98.6%, respectively. Furthermore, the dynamic viscosity of the demetallized extra-heavy oil was measured, and the ash content of the petroleum coke product produced using the demetallized extra-heavy oil obtained in this embodiment as raw material was also measured.

[0112] Comparative Example 1

[0113] This comparative example demonstrates the energy-saving and consumption-reducing effects of using an electrostatic desalting unit to remove metal elements from crude oil under conditions of adding and not adding the demetallizing agent MPT01. The difference between this comparative example and Example 1 is that no crude oil demetallizing agent MPT01 is added during the deep pretreatment demetallization of crude oil. Without MPT01, the electric field current in the primary electrostatic desalting tank exceeds 200A, and the electric field current in the secondary electrostatic desalting tank is as high as 170-180A. However, after adding MPT01 and once the electrostatic desalting unit reaches stable operation again, the electric field currents in the primary and secondary electrostatic desalting tanks are 120A and 90A, respectively. Compared with the electric field currents in the primary and secondary electrostatic desalting tanks without the demetallizing agent, the current reduction is within the range of 40-50%, demonstrating a significant energy-saving and consumption-reducing effect.

[0114] Comparative Example 2

[0115] This comparative example is similar to Example 2, except that the crude oil demetallizing agent MPT02 is not added during the crude oil deep pretreatment demetallization.

[0116] Analysis of the metal element occurrence states in the crude oil transported through the Yichang pipeline revealed the following: 60.8% of calcium exists as water-soluble inorganic salts, and 20.5% exists as petroleum salts; sodium mainly exists as water-soluble inorganic salts, accounting for 81.5%; nickel mainly exists as porphyrin and non-porphyrin compounds, with porphyrin nickel accounting for 13.9% and non-porphyrin nickel accounting for 79.9%; 62.0% of iron exists as inorganic salts and petroleum salts, and 38.0% exists as porphyrin and non-porphyrin compounds; 8.3% of vanadium exists as water-soluble salts, and 91.7% exists as porphyrin and non-porphyrin compounds. These results indicate that, except for calcium and sodium, over 50% of other elements exist in the pipeline crude oil as oil-soluble metal compounds.

[0117] Analysis of the content of five major metallic elements in crude oil showed that the contents of Ca, Fe, Ni, Na, and V were 38.3, 33.0, 17.5, 7.6, and 4.6 μg / g, respectively. When the crude oil demetallizing agent MPT02 was not added, after electro-desalting using an electro-desalting unit, the contents of Ca, Fe, Ni, Na, and V were 26.6, 24.6, 16.9, 1.2, and 4.5 μg / g, respectively. The removal rates of Ca, Fe, Ni, Na, and V were 30.5%, 25.5%, 3.4%, 84.2%, and 2.2%, respectively. Except for sodium, the removal rates were all lower than those of water-soluble inorganic salts. The proportions of metals present in the form of water-soluble inorganic salts were measured. When 125 μg / g of crude oil demetallizing agent MPT02 was added, after crude oil was desalted using an electro-desalting device, the contents of Ca, Fe, Ni, Na, and V decreased to 2.6, 14.7, 16.1, 0.4, and 4.1 μg / g, respectively. The corresponding removal rates of metal elements were 93.2%, 55.5%, 8.0%, 94.7%, and 10.9%, respectively, all of which were much higher than the proportions of the relevant metal elements present in the form of water-soluble inorganic salts. This indicates that the added crude oil demetallizing agent MPT02 can effectively remove metal elements present in pipeline crude oil in the form of oil-soluble organometallic compounds.

[0118] Comparative Example 3

[0119] This comparative example is similar to Example 3, except that the crude oil demetallizing agent MPT03 is not added during the crude oil deep pretreatment demetallization.

[0120] Under the same operating conditions of the electrostatic desalting unit without using MPT03 crude oil demetallizing agent, the removal rates of calcium, iron, sodium, nickel, and vanadium in crude oil were 47.5%, 42.2%, 89.2%, 0.0%, and 0.0%, respectively. However, after adding 150 μg / g of MPT03 crude oil demetallizing agent for deep metal pretreatment, the removal rates of calcium, iron, sodium, nickel, and vanadium in the crude oil were 94.4%, 94.1%, 99.6%, 9.2%, and 5.0%, with a total removal rate of 66.7% for the five metal elements.

[0121] The comparison shows that the MPT03 crude oil demetallizer effectively removes oil-soluble metal elements from crude oil.

[0122] Comparative Example 4

[0123] This comparative example is similar to Example 4, except that the crude oil demetallizing agent MPT04 is not added during the crude oil deep pretreatment demetallization.

[0124] Under the same operating conditions of the electrostatic desalting unit without using MPT04 crude oil demetallizing agent, the removal rates of calcium, iron, sodium, and nickel in crude oil were 21.5%, 24.2%, 89.2%, and 0.0%, respectively. However, after adding 150 μg / g of MPT04 crude oil demetallizing agent for deep metal pretreatment, the removal rates of calcium, iron, sodium, and nickel in the crude oil were 48.4%, 54.1%, 91.6%, and 35.0%, respectively. This comparison shows that MPT04 crude oil demetallizing agent can effectively remove oil-soluble metal elements from crude oil, especially nickel, which mainly exists in the form of oil-soluble porphyrins.

[0125] Comparative Example 5

[0126] This comparative example is similar to Example 5, except that the crude oil demetallizing agent MPT05 is not added during the crude oil deep pretreatment demetallization.

[0127] Under the same operating conditions of the electro-desalting unit without using MPT05 crude oil demetallizer, the removal rates of calcium, iron, sodium, and nickel in crude oil were 36.8%, 21.4%, 89.2%, and 0.0%, respectively. However, after adding 60 μg / g of MPT05 crude oil demetallizer for deep metal pretreatment, the removal rates of calcium, iron, sodium, and nickel in the crude oil were 82.2%, 54.4%, 100.0%, and 8.8%, respectively. This comparison shows that MPT05 crude oil demetallizer can effectively remove oil-soluble metal elements from crude oil.

[0128] Comparative Example 6

[0129] This comparative example provides a control experiment using only an electro-desalting device for demetallization without the addition of the demetallizing agent MPT06. This experiment verifies the effect of the MPT06 crude oil demetallizing agent used in Example 6 on reducing crude oil viscosity and lowering petroleum coke ash content and quality. The difference between this comparative example and Example 6 is that MPT06 was not added during the demetallization of the extra-heavy oil. The dynamic viscosity of the extra-heavy oil before and after demetallization was measured at 50°C using a HADV-II+ rotational viscometer manufactured by Brookfield Laboratories, USA. The results show that the dynamic viscosity of the extra-heavy oil decreased from 1316 mPa·s before demetallization to 878 mPa·s, a reduction rate of 33.3%. However, after adding MPT06, the dynamic viscosity of the extra-heavy oil sample at 50°C decreased from 1316 mPa·s before demetallization to 632 mPa·s, a reduction rate of 52.0%. The above results indicate that the dynamic viscosity of the extra-heavy oil sample after demetallization is significantly lower than that before demetallization. This suggests that the demetallization process of extra-heavy oil is essentially a process of partial modification of the oil. The reduction in the metal content of the extra-heavy oil leads to a decrease in its dynamic viscosity, making it easier to transport and reducing the power consumption of transporting extra-heavy oil.

[0130] The ash content of petroleum coke obtained from the coking of demetallized extra-heavy oil was determined, showing a value of 1.02 wt.%, classifying it as grade 3B petroleum coke. However, after adding the crude oil demetallizing agent MPT06, the ash content of the petroleum coke obtained from the coking of demetallized extra-heavy oil was measured, showing a value of 0.46 wt.%, lower than 0.50 wt.%, classifying it as grade 1B petroleum coke. These results indicate that the ash content of petroleum coke obtained from coking using demetallized extra-heavy oil as raw material is significantly reduced after demetallization treatment. This demonstrates that demetallization treatment of extra-heavy oil has a significant effect on reducing the ash content of subsequent petroleum coke products, improving the quality of petroleum coke products, enhancing the market competitiveness of petroleum coke products, and improving the economic benefits of enterprises.

[0131] Comparative Example 7

[0132] This comparative example is similar to Example 3, except that ethylene glycol solvent is not added during the preparation of the crude oil demetallizing agent, and water is used as the solvent instead.

[0133] When the demetallizing agent solution prepared using water as a solvent is cooled to 0°C, a large amount of solid precipitates out within 12 hours. After the temperature is restored to room temperature and allowed to stand, a large amount of solid material still remains in the solution.

[0134] The crude oil demetallizing agent MPT03 solution, prepared using ethylene glycol solvent, did not freeze or precipitate any solids during a 6-day experiment when the temperature was maintained at -30℃. Subsequent observation at room temperature showed no further solid precipitation. This solution meets the requirements for use in the harsh winter climates of northern and even northeastern regions.

[0135] Comparative Example 8

[0136] This comparative example is similar to Example 4, except that dimethylimidazole corrosion inhibitor is not added during the preparation of the crude oil demetallizing agent.

[0137] Corrosion tests were conducted according to ASTM G31-995 standard. At 50℃, the corrosion of 20# carbon steel by crude oil demetallizer without dimethylimidazole corrosion inhibitor was investigated. The results showed that after 72 hours of constant-temperature simulated corrosion testing, the corrosion rate of this demetallizer on 20# carbon steel was 1.4458 mm / a, with a corrosion grade of 8, indicating it was not corrosion-resistant. Under the same experimental conditions, the corrosion rate of the crude oil demetallizer MPT04 on 20# carbon steel was 0.0970 mm / a, with a corrosion grade of 5, indicating it was corrosion-resistant.

[0138] Therefore, adding dimethylimidazole corrosion inhibitor during the preparation of crude oil demetallizer can significantly reduce the corrosion rate of crude oil demetallizer on storage tanks and demetallizer injection pipelines, and improve their corrosion level from non-corrosion resistant to corrosion resistant.

[0139] Comparative Example 9

[0140] This comparative example is similar to Example 5, except that monoethanolamine is not added during the preparation of the crude oil demetallizing agent.

[0141] For crude oil demetallizers without added monoethanolamine, the pH value measured using precision pH test paper is 2–3; while for crude oil demetallizer MPT05 with added monoethanolamine, the pH value measured using precision pH test paper is 5–6.

[0142] Therefore, adding monoethanolamine during the preparation of crude oil demetallizer can significantly increase the pH value of the crude oil demetallizer, thereby reducing its corrosion rate on storage tanks and demetallizer injection pipelines.

[0143] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. 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 claims of the present invention.

Claims

1. A crude oil demetallizing agent for removing oil-soluble metal elements from crude oil, characterized in that, It is prepared from carboxylic acid compounds, alkanolamine compounds, amide compounds, corrosion inhibitors, surfactants, and solvents; wherein, the carboxylic acid compounds are 5-50 parts by weight, the alkanolamine compounds are 1-30 parts by weight, the amide compounds are 3-25 parts by weight, the corrosion inhibitors are 0.05-5 parts by weight, the surfactants are 0.1-2 parts by weight, and the solvents are 10-90 parts by weight.

2. The crude oil demetallizing agent for removing oil-soluble metal elements from crude oil according to claim 1, characterized in that, The carboxylic acid compounds include any one or more monocarboxylic acids or polycarboxylic acids.

3. The crude oil demetallizing agent for removing oil-soluble metal elements from crude oil according to claim 1, characterized in that, The alkanolamine compounds include any one or more of ethanolamine, propanolamine, diethanolamine, diisopropanolamine, triethanolamine, and butanolamine.

4. The crude oil demetallizing agent for removing oil-soluble metal elements from crude oil according to claim 1, characterized in that, The corrosion inhibitor comprises any one or more of amino acid compounds, aniline aldehyde condensates, and imidazole compounds.

5. The crude oil demetallizing agent for removing oil-soluble metal elements from crude oil according to claim 1, characterized in that, The solvent is any one or more of methanol, ethanol, ethylene glycol, n-propanol, and isopropanol.

6. The crude oil demetallizing agent for removing oil-soluble metal elements from crude oil according to claim 1, characterized in that, The amide compounds include any one or more of formamide, acetamide, propionamide, and benzamide.

7. The crude oil demetallizing agent for removing oil-soluble metal elements from crude oil according to claim 1, characterized in that, The mass ratio of the carboxylic acid compound to the amide compound is 1:0.8 to 1.

2.

8. The application of a crude oil demetallizing agent for removing oil-soluble metal elements from crude oil as described in any one of claims 1 to 7, characterized in that, Used for deep pretreatment and demetallization of crude oil.

9. A method for deep pretreatment and demetallization of crude oil, characterized in that, Includes the following steps: S1. Preheat the crude oil, then add the crude oil demetallizing agent for removing oil-soluble metal elements from the crude oil as described in any one of claims 1-7, water and demulsifier, and after thorough mixing and reaction, obtain an oil-water emulsion; S2. The oil-water emulsion obtained in step S1 is injected into an electro-desalting device for conventional electro-desalting and demetallization treatment to obtain crude oil with metal elements removed. The electro-desalination device includes a primary electro-desalination tank and a secondary electro-desalination tank.

10. The crude oil deep pretreatment demetallization method according to claim 9, characterized in that, The crude oil preheating temperature in step S1 is 100-165℃; the amount of water used in step S1 is 3-7 wt.%; and the amount of crude oil demetallizing agent used in step S1 is 50-1500 μg / g.