A method and system for treating oil sludge

Abstract

The present disclosure relates to a method and system for treating oil sludge, the method comprising the following steps: S1, mixing and stirring the oil sludge, poor-quality hydrocarbon oil and cleaning agent for extraction treatment to obtain a solid-liquid mixture; S2, performing solid-liquid separation treatment on the solid-liquid mixture to obtain a solid phase and a liquid phase; S3, mixing the liquid phase with a pH regulator and a demulsifier, and performing oil-water separation treatment on the obtained mixed liquid to obtain a water phase and an oil phase; wherein the cleaning agent is a water-soluble cleaning agent. By using a water-soluble cleaning agent to mix with the oil sludge and the poor-quality hydrocarbon oil, and adjusting the pH, the cleaning agent can be regenerated and recycled, the treatment cost is reduced, and the separation efficiency is improved.

Description

Technical Field

[0001] This disclosure relates to the field of sludge treatment, and more specifically, to a method and system for treating sludge. Background Technology

[0002] Oily sludge is an oily sludge formed in petrochemical enterprises during the extraction, storage, transportation, and refining of crude oil, resulting from contact between crude oil or other oil products and sediment. Its main components are oil, water, and mud, and these three phases easily form a stable system that is difficult to treat. In addition to oil, oily sludge also contains heavy metal ions (such as iron, copper, and nickel) and has a high salt content. Oily sludge in production systems increases system operating pressure and causes additional energy consumption. Furthermore, the cleaned-up oily sludge contains toxic and harmful substances such as sulfides, benzene compounds, and phenols; improper treatment can pollute water bodies and soil, causing water quality deterioration and excessive levels of petroleum compounds in the soil, thus impacting the ecological environment.

[0003] Currently, oil sludge has been classified as hazardous solid waste by the state and is managed accordingly. With increasingly stringent national environmental protection requirements, the reduction, harmlessness, and resource utilization of oil sludge will become an inevitable trend in the development of its treatment technologies. Therefore, the economical and effective treatment and utilization of oil sludge is of significant practical importance to the development of the petrochemical industry.

[0004] Currently, the main technologies for treating oily sludge include incineration, pyrolysis, biological treatment, and solvent extraction, each with its own advantages, disadvantages, and applicable scope. Incineration is costly, may cause secondary pollution, and the oil content in the sludge is not effectively utilized. Pyrolysis requires specific reaction conditions, involves high equipment investment, and is complex to operate. Biological treatment has a long cycle, requires a large equipment footprint, and is greatly affected by environmental climate. Solvent extraction is considered a better method for treating oily sludge, with advantages such as a simple process and the ability to recover and reuse the oil content. However, existing solvent extraction methods use expensive extractants, and the recovery process is complex, resulting in high costs for oily sludge treatment. Summary of the Invention

[0005] The purpose of this disclosure is to provide a method and system for treating oil sludge. After appropriate treatment of the oil sludge, the recovered oil is passed through an electro-desalting device to meet the conditions for refining. The cleaning agent is recyclable, the cost is low, and it is suitable for industrial applications.

[0006] To achieve the above objectives, the first aspect of this disclosure provides a method for treating oil sludge, the method comprising the following steps:

[0007] S1. Mix oil sludge, inferior hydrocarbon oil and cleaning agent and perform stirring and extraction to obtain a solid-liquid mixture;

[0008] S2. Perform solid-liquid separation treatment on the solid-liquid mixture to obtain a solid phase and a liquid phase;

[0009] S3. Mix the liquid phase with a pH adjuster and a demulsifier, and perform oil-water separation treatment on the resulting mixture to obtain an aqueous phase and an oil phase;

[0010] The cleaning agent is a water-soluble cleaning agent.

[0011] Optionally, the method further includes: returning the aqueous phase from step S3 as the cleaning agent to step S1 for continued use.

[0012] Optionally, in step S1, the stirring extraction process includes: first mixing the inferior hydrocarbon oil and the sludge and stirring for 5-30 minutes, then adding the cleaning agent and continuing to stir.

[0013] Optionally, in step S1, the mass ratio of the sludge to the inferior hydrocarbon oil is 1:(1-6); the amount of cleaning agent added relative to the total mass of the sludge is 500-3000 mg / kg.

[0014] Optionally, in step S1, the stirring extraction process is carried out in a stirring extractor, and the conditions of the stirring extraction process include: mechanical stirring, temperature of 50-90℃, rotation speed of 100-600 rpm, and time of 20-90 min.

[0015] Optionally, in step S2, the solid-liquid separation process includes: pumping the solid-liquid mixture sequentially into a primary centrifuge and a secondary centrifuge for centrifugal separation.

[0016] Optionally, the speed of the primary centrifuge is 2000-3000 rpm, and the speed of the secondary centrifuge is 3000-4000 rpm;

[0017] Optionally, the rotational speed of the primary centrifuge is lower than that of the secondary centrifuge.

[0018] Optionally, step S1 further includes: diluting the cleaning agent with deionized water to a mass fraction of 2-10%, wherein the cleaning agent includes one or more of sodium carboxylate, ammonium carboxylate, sodium alkyl sulfonate, sodium benzenesulfonate, and polyetheramine; wherein the weight average molecular weight of the polyetheramine is 200-2000;

[0019] The inferior hydrocarbon oil includes one or more of the following: catalytic diesel oil, catalytic slurry oil, catalytic light cycle oil, catalytic heavy cycle oil, recovered light waste oil, and recovered heavy waste oil.

[0020] Optionally, in step S3, the mass fraction of the pH adjuster is 10-20%, the mass ratio of the pH adjuster to the liquid phase is (0.01-0.03):1, and the pH adjuster includes one or more of hydrochloric acid, sulfuric acid, nitric acid, formic acid, acetic acid, propionic acid, butyric acid, malic acid, and citric acid.

[0021] The amount of demulsifier added relative to the total volume of the liquid phase is 100-500 mg / L. The demulsifier is selected from one or more of RP-01 type demulsifier, RP-02 type demulsifier and RP-03 type demulsifier, preferably RP-02 type demulsifier.

[0022] Optionally, in step S3, the oil-water separation process includes: mixing the mixture in a static mixer, and then separating the aqueous phase and the oil phase in a cleaning agent regeneration device. The operating conditions of the cleaning agent regeneration device include: a temperature of 50-90°C and a time of 30-120 min.

[0023] Optionally, the method further includes: sending the oil phase obtained in step S3 into an electric desalting unit for desalting, and then reprocessing it.

[0024] A second aspect of this disclosure provides a system for treating sludge using the method described in the first aspect of this disclosure, the system comprising:

[0025] A stirred extractor, comprising a low-quality hydrocarbon oil inlet, a cleaning agent inlet, an oil sludge inlet, and a solid-liquid mixture outlet;

[0026] A solid-liquid separation device includes a solid-liquid mixture inlet, a solid phase outlet, and a liquid phase outlet; wherein the solid-liquid mixture inlet is connected to the solid-liquid mixture outlet.

[0027] An oil-water separation unit includes a liquid phase inlet, a pH adjuster inlet, a demulsifier inlet, an aqueous phase outlet, and an oil phase outlet; wherein the liquid phase inlet is connected to the liquid phase outlet, and the aqueous phase outlet is connected to the cleaning agent inlet.

[0028] Optionally, the oil-water separation unit includes a static mixer and a cleaning agent regeneration device;

[0029] The static mixer includes a liquid phase inlet, a mixture outlet, a pH adjuster inlet, and a demulsifier inlet;

[0030] The cleaning agent regeneration device includes a mixture inlet, an aqueous phase outlet, and an oil phase outlet;

[0031] The mixture outlet is connected to the mixture inlet.

[0032] Optionally, the system further includes an electro-desalination device, which includes an oil phase inlet and an oil separation outlet; wherein the oil phase inlet is connected to the oil phase outlet of the cleaning agent regeneration device.

[0033] Through the above technical solution, the method disclosed herein uses water-soluble cleaning agent and inferior hydrocarbon oil to treat oil sludge. The oil sludge is mixed with water-soluble cleaning agent and inferior hydrocarbon oil and the pH is adjusted, which allows the cleaning agent to be regenerated and recycled in a simple way, reducing the treatment cost, improving the separation efficiency and the recovery rate of oil products, and is suitable for industrial applications.

[0034] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0035] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0036] Figure 1 This is a schematic diagram of the sludge treatment system disclosed herein.

[0037] Explanation of reference numerals in the attached figures

[0038] 1. Oil sludge 2. Inferior hydrocarbon oil 3. Cleaning agent

[0039] 4. Aqueous phase; 5. pH adjuster and demulsifier; 6. Solid phase

[0040] 7. Liquid phase; 8. Oil phase; 9. Stirred extractor

[0041] 10. Cleaning agent regeneration unit; 11. Static mixer; 12. Electro-desalination unit.

[0042] 13. Atmospheric pressure reducing device; 14. Primary centrifuge; 15. Secondary centrifuge.

[0043] 16. Pump Detailed Implementation

[0044] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0045] The first aspect of this disclosure provides a method for treating sludge, the method comprising the following steps:

[0046] S1. Mix oil sludge, inferior hydrocarbon oil and cleaning agent and perform stirring and extraction to obtain a solid-liquid mixture;

[0047] S2. Perform solid-liquid separation treatment on the solid-liquid mixture to obtain a solid phase and a liquid phase;

[0048] S3. Mix the liquid phase with a pH adjuster and a demulsifier, and perform oil-water separation treatment on the resulting mixture to obtain an aqueous phase and an oil phase;

[0049] The cleaning agent is a water-based cleaning agent.

[0050] In this disclosure, the oil sludge needs to be pretreated before processing, and the pretreatment involves removing impurities from the oil sludge. The cleaning agent acts as a surfactant, disrupting the stable three-phase system of oil, water, and solid in the oil sludge under stirring conditions, thereby enhancing the extraction process.

[0051] The method disclosed herein can achieve good treatment results for oil sludge of various sources and properties. In one embodiment, the oil sludge used can be at least one of the following: oil sludge from the bottom of storage tanks, oil separator bottom sludge, and oilfield landfill sludge. The weight ratio of water, mud and oil in the oil sludge can be 1:(1-8):(1-8).

[0052] According to a specific embodiment of this disclosure, in order to obtain better separation effect and reduce the amount of cleaning agent used, step S1, the stirring extraction process includes: first mixing the inferior hydrocarbon oil and sludge and stirring for 5-30 minutes, then adding the cleaning agent and continuing stirring. The stirring extraction process is carried out in a stirred extractor, and the conditions for the stirring extraction process include: mechanical stirring, a temperature of 50-90℃, a rotation speed of 100-600 rpm, and a time of 20-90 minutes; preferably, a temperature of 70-80℃, a rotation speed of 200-400 rpm, and a time of 30-60 minutes.

[0053] According to a specific embodiment of this disclosure, in step S1, the mass ratio of sludge to inferior hydrocarbon oil is 1:(1-6), preferably 1:(2-3); relative to the total mass of sludge, the amount of cleaning agent added is 500-3000 mg / kg, preferably 1000-2000 mg / kg. The inferior hydrocarbon oil is mainly used for conditioning the sludge and improving its fluidity, while the cleaning agent is mainly used for removing oil from the surface of solid particles.

[0054] According to this disclosure, step S1 further includes: diluting the cleaning agent with deionized water to a mass fraction of 2-10%, preferably 3-5%. This operation improves the flowability of the cleaning agent, reduces the dosage, and lowers processing costs. The cleaning agent is a water-soluble cleaning agent, including one or more of sodium carboxylate, ammonium carboxylate, sodium alkyl sulfonate, sodium benzenesulfonate, and polyetheramine; preferably one or more of sodium carboxylate, sodium alkyl sulfonate, and polyetheramine. The polyetheramine has a weight-average molecular weight of 200-2000; preferably 400-600. Sodium carboxylate can be, for example, one or more of sodium stearate, sodium palmitate, and sodium oleate; sodium alkyl sulfonate can be, for example, one or more of sodium dodecyl sulfonate, sodium hexadecyl sulfonate, and sodium octadecyl sulfonate; and ammonium carboxylate can be, for example, one or more of ammonium stearate, ammonium palmitate, and ammonium oleate. The cleaning agent used in this invention can control its surface activity, acting as a surfactant during use and reducing its surface activity when regeneration is required, thus facilitating demulsification and oil-water separation.

[0055] According to a specific embodiment of this disclosure, the inferior hydrocarbon oil includes one or more of catalytic diesel, catalytic slurry oil, catalytic light cycle oil, catalytic heavy cycle oil, recovered light sludge oil, and recovered heavy sludge oil, preferably one or more of catalytic diesel, catalytic light cycle oil, and catalytic heavy cycle oil; this is conventional in the art, and will not be elaborated further in this invention.

[0056] According to a specific embodiment of this disclosure, step S2, the solid-liquid separation process includes: sequentially pumping the solid-liquid mixture into a primary centrifuge and a secondary centrifuge for centrifugal separation. The primary centrifuge operates at a speed of 2000-3000 rpm, preferably 3000 rpm; the secondary centrifuge operates at a speed of 3000-4000 rpm, preferably 4000 rpm. In one embodiment, the speed of the primary centrifuge is lower than that of the secondary centrifuge. This operation allows for more thorough separation of the solid and liquid, reducing the content of mechanical impurities in the liquid. The solid residue obtained after centrifugal separation can be used as fuel.

[0057] According to a specific embodiment of this disclosure, in step S3, the mass fraction of the pH adjuster is 10-20%. The mass ratio of the pH adjuster to the liquid phase is (0.01-0.03):1; the pH adjuster includes one or more of hydrochloric acid, sulfuric acid, nitric acid, formic acid, acetic acid, propionic acid, butyric acid, malic acid, and citric acid; preferably one or more of citric acid, acetic acid, and malic acid; the amount of demulsifier added relative to the total volume of the liquid phase is 100-500 mg / L, preferably 200-300 mg / L; the demulsifier is selected from one or more of RP-01 type demulsifier, RP-02 type demulsifier, and RP-03 type demulsifier, preferably RP-02 type demulsifier, whose component is glycerol polyoxyethylene polyoxypropylene ether. The pH adjuster is used to adjust the pH value of the liquid phase, inhibit the surface activity of the cleaning agent, enable the cleaning agent to undergo subsequent cleaning agent regeneration processes, and reduce processing costs; the demulsifier is used for demulsification of the liquid phase.

[0058] According to one specific embodiment of this disclosure, the method further includes: returning the aqueous phase from step S3 as a cleaning agent to step S1 for continued use. This operation can improve the utilization rate of the cleaning agent and reduce processing costs.

[0059] According to a specific embodiment of this disclosure, in step S3, the oil-water separation process includes: mixing the mixture in a static mixer, and then separating the aqueous phase and the oil phase in a cleaning agent regeneration device; furthermore, the aqueous phase can be returned to step S1 as a cleaning agent for continued use, and optionally, the oil phase can be sent to a refining unit for reprocessing.

[0060] In the above embodiments, the operating conditions of the cleaning agent regeneration device further include: a temperature of 50-90°C, preferably 70-80°C; and a time of 30-120 min, preferably 60-90 min.

[0061] According to this disclosure, the method further includes: sending the oil phase obtained in step S3 into an electric desalting unit for desalting, and then reprocessing the desalted oil phase, for example, by sending it into an atmospheric and vacuum distillation unit for fractionation.

[0062] A second aspect of this disclosure provides a system for treating sludge using the method described in the first aspect of this disclosure, the system comprising:

[0063] A stirred extractor, comprising a low-quality hydrocarbon oil inlet, a cleaning agent inlet, an oil sludge inlet, and a solid-liquid mixture outlet;

[0064] A solid-liquid separation device includes a solid-liquid mixture inlet, a solid phase outlet, and a liquid phase outlet; wherein the solid-liquid mixture inlet is connected to the solid-liquid mixture outlet.

[0065] An oil-water separation unit includes a liquid phase inlet, a pH adjuster inlet, a demulsifier inlet, an aqueous phase outlet, and an oil phase outlet; wherein the liquid phase inlet is connected to the liquid phase outlet, and the aqueous phase outlet is connected to the cleaning agent inlet.

[0066] According to a specific embodiment of this disclosure, the oil-water separation unit includes a static mixer and a cleaning agent regeneration device. The static mixer includes a liquid phase inlet, a mixed liquid outlet, a pH adjuster inlet, and a demulsifier inlet. The cleaning agent regeneration device includes a mixed liquid inlet, an aqueous phase outlet, and an oil phase outlet. The mixed liquid outlet is connected to the mixed liquid inlet.

[0067] According to one specific embodiment of this disclosure, the system further includes: an electro-desalting device, which includes an oil phase inlet and an oil separation outlet; wherein the oil phase inlet is connected to the oil phase outlet of the cleaning agent regeneration device. In a further embodiment, the oil separation outlet of the electro-desalting device can be connected to the feed inlet of a refining unit, for example, the oil separation outlet can be connected to the feed inlet of an atmospheric and vacuum distillation unit.

[0068] In this disclosure, the electro-desalination device also includes a water inlet and a wastewater outlet.

[0069] In this disclosure, “connection” includes both direct connection and indirect connection.

[0070] Unless otherwise specified, all reagents used in the embodiments and comparative examples of this application are commercially available.

[0071] Examples 1-6 illustrate the methods and systems for treating oil sludge according to this disclosure.

[0072] Example 1

[0073] Adopting such Figure 1 The sludge treatment system shown is used to treat sludge. The specific steps are as follows:

[0074] Inferior hydrocarbon oil 2, cleaning agent 3, and sludge 1 (water, sludge, and oil in a weight ratio of 1:2:7) were added to an extraction stirrer 9 for stirring and extraction. The mass ratio of sludge to inferior hydrocarbon oil was 1:3. The amount of cleaning agent added was 1500 mg / kg relative to the total mass of the sludge. The temperature of the stirring extractor 9 was 80℃, the rotation speed was 300 rpm, and the time was 60 min. The inferior hydrocarbon oil was catalytic diesel (Changling Refining & Chemical), the cleaning agent was sodium stearate (3% by mass), and the sludge was bottom sludge from the storage tank. The amount of cleaning agent added was based on the weight of sodium stearate.

[0075] After extraction, the solid-liquid mixture in the stirred extractor 9 is sequentially pumped into a primary centrifuge 14 and a secondary centrifuge 15 for solid-liquid separation, yielding a liquid phase 7 and a solid phase 6. The primary centrifuge 14 operates at 3000 rpm, and the secondary centrifuge 15 operates at 4000 rpm. A demulsifier and a pH adjuster 5 are added to the separated liquid phase 7 to obtain a mixture. The demulsifier is RP-02 type demulsifier (200 mg / L relative to the total volume of the liquid phase), manufactured by Linhua Water Stabilizer Factory. The pH adjuster is 10% citric acid, with a pH adjuster-to-liquid phase 7 mass ratio of 0.01:1. The mass of the pH adjuster is based on the mass of citric acid.

[0076] The mixture is fed into a static mixer 11 for mixing, and then into a cleaning agent regeneration unit 10. The operating conditions are: temperature 80℃, time 120 min. The separated aqueous phase 4 is led out of the system. The separated oil phase 8 is fed into an electrostatic desalting unit 12 for desalting, and then into an atmospheric and vacuum distillation unit 13 for fractionation. The processed oil products are tested, and the results are shown in Table 1.

[0077] Example 2

[0078] The method described in Example 1 was used to treat the bottom sludge of the storage tank, except that the cleaning agent used was the regenerated cleaning agent from Example 1. The resulting oil products were tested, and the results are shown in Table 1. The separated aqueous phase was then extracted through a system.

[0079] Example 3

[0080] The method in Example 1 was used to treat the bottom sludge of the storage tank. The only difference was that the cleaning agent used was the regenerated cleaning agent in Example 2. The oil products obtained after treatment were tested, and the results are shown in Table 1.

[0081] Example 4

[0082] The method described in Example 1 was used to treat the bottom sludge of the storage tank. The only difference was that the sludge and catalytic diesel were first added to a stirred extractor and mixed and stirred for 10 minutes. Then, sodium stearate was added, and stirring was continued for 50 minutes. The resulting oil products were tested, and the results are shown in Table 1. The separated aqueous phase was extracted using a system.

[0083] Example 5

[0084] The method in Example 4 was used to treat the bottom sludge of the storage tank. The only difference was that the cleaning agent used was the regenerated cleaning agent in Example 4. The oil products obtained after treatment were tested, and the results are shown in Table 1.

[0085] Example 6

[0086] The method in Example 1 was used to treat the bottom sludge of the storage tank. The only difference was that the inferior hydrocarbon oil used was recycled light sludge oil. The oil products obtained after treatment were tested, and the results are shown in Table 1.

[0087] Comparative Example 1

[0088] The method described in Example 1 was used to treat the bottom sludge of the storage tank, except that an equal mass of deionized water was used instead of catalytic diesel. The resulting oil products were tested, and the results are shown in Table 1.

[0089] Comparative Example 2

[0090] The method described in Example 1 was used to treat the bottom sludge of the storage tank, except that the cleaning agent was calcium naphthenate. The oil products obtained after the treatment were tested, and the results are shown in Table 1.

[0091] Table 1

[0092]

[0093]

[0094] According to the data in Table 1, the method and system for treating oil sludge disclosed herein enable the recycling of cleaning agents, reducing treatment costs, and achieving high oil separation efficiency. Through a comparison of Examples 1-6 and Comparative Examples 1-2 of this application, it is evident that adding inferior hydrocarbon oil and water-based cleaning agents can achieve better oil separation results. Furthermore, through a comparison of Examples 1-3 and 4-5, it is clear that the method of first adding oil sludge and inferior hydrocarbon oil, stirring and mixing, and then adding the cleaning agent can further improve the recovery rate and separation efficiency of oil products.

[0095] The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0096] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0097] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for treating oil sludge, characterized in that, The method includes the following steps: S1. Mix oil sludge, inferior hydrocarbon oil and cleaning agent and perform stirring and extraction to obtain a solid-liquid mixture; In step S1, the stirring extraction process includes: first mixing the inferior hydrocarbon oil and the sludge and stirring for 5-30 minutes, then adding the cleaning agent and continuing to stir; S2. Perform solid-liquid separation treatment on the solid-liquid mixture to obtain a solid phase and a liquid phase; S3. Mix the liquid phase with the pH adjuster and the demulsifier, and perform oil-water separation treatment on the resulting mixture to obtain an aqueous phase and an oil phase; The cleaning agent is a water-soluble cleaning agent; The cleaning agent includes one or more of sodium carboxylate, ammonium carboxylate, and polyetheramine; The weight ratio of water, mud, and oil in the sludge is 1:(1-8):(1-8). The pH adjuster has a mass fraction of 10-20%, and the mass ratio of the pH adjuster to the liquid phase is (0.01-0.03):

1. The pH adjuster includes one or more of hydrochloric acid, sulfuric acid, nitric acid, formic acid, acetic acid, propionic acid, butyric acid, malic acid, and citric acid. The method further includes: returning the aqueous phase obtained in step S3 as the cleaning agent to step S1 for continued use; sending the oil phase obtained in step S3 into an electro-desalting device for desalting, and then reprocessing it; In step S1, the mass ratio of the sludge to the inferior hydrocarbon oil is 1:(1-6); the amount of cleaning agent added relative to the total mass of the sludge is 500-3000 mg / kg.

2. The method according to claim 1, wherein, In step S1, the stirring extraction process is carried out in a stirring extractor. The conditions for the stirring extraction process include: mechanical stirring, temperature of 50-90℃, rotation speed of 100-600 rpm, and time of 20-90 min.

3. The method according to claim 1, wherein, In step S2, the solid-liquid separation process includes: pumping the solid-liquid mixture sequentially into a primary centrifuge and a secondary centrifuge for centrifugal separation.

4. The method according to claim 3, wherein, The speed of the first-stage centrifuge is 2000-3000 rpm, and the speed of the second-stage centrifuge is 3000-4000 rpm.

5. The method according to claim 3, wherein, The rotational speed of the primary centrifuge is lower than that of the secondary centrifuge.

6. The method according to claim 1, wherein, Step S1 further includes: diluting the cleaning agent with deionized water to a mass fraction of 2-10%; The weight-average molecular weight of the polyether amine is 200-2000; The inferior hydrocarbon oil includes one or more of the following: catalytic diesel oil, catalytic slurry oil, catalytic light cycle oil, catalytic heavy cycle oil, recovered light waste oil, and recovered heavy waste oil.

7. The method according to claim 1, wherein, In step S3, the amount of demulsifier added relative to the total volume of the liquid phase is 100-500 mg / L, and the demulsifier is selected from one or more of RP-01 type demulsifier, RP-02 type demulsifier and RP-03 type demulsifier.

8. The method according to claim 7, wherein, The demulsifier is RP-02 type demulsifier.

9. The method according to claim 1, wherein, In step S3, the oil-water separation process includes: mixing the mixture in a static mixer, and then separating the water phase and the oil phase in a cleaning agent regeneration device. The operating conditions of the cleaning agent regeneration device include: a temperature of 50-90℃ and a time of 30-120 min.

10. A system for treating oil sludge using the method described in any one of claims 1-9, characterized in that, The system includes: A stirred extractor, comprising a low-quality hydrocarbon oil inlet, a cleaning agent inlet, an oil sludge inlet, and a solid-liquid mixture outlet; A solid-liquid separation device includes a solid-liquid mixture inlet, a solid phase outlet, and a liquid phase outlet; wherein the solid-liquid mixture inlet is connected to the solid-liquid mixture outlet. An oil-water separation unit includes a liquid phase inlet, a pH adjuster inlet, a demulsifier inlet, an aqueous phase outlet, and an oil phase outlet; wherein the liquid phase inlet is connected to the liquid phase outlet, and the aqueous phase outlet is connected to the cleaning agent inlet.

11. The system according to claim 10, wherein, The oil-water separation unit includes a static mixer and a cleaning agent regeneration device; The static mixer includes a liquid phase inlet, a mixture outlet, a pH adjuster inlet, and a demulsifier inlet; The cleaning agent regeneration device includes a mixture inlet, an aqueous phase outlet, and an oil phase outlet; The mixture outlet is connected to the mixture inlet.

12. The system according to claim 10, wherein, The system also includes an electro-desalination device, which includes an oil phase inlet and an oil separation outlet; wherein the oil phase inlet is connected to the oil phase outlet of the cleaning agent regeneration device.

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