A method for deacidifying vacuum distillate oil

Abstract

This invention relates to the field of distillate oil refining technology and discloses a method for deacidifying vacuum distillate oil. The method includes: S10, deacidifying the vacuum distillate oil and a deacidifying agent in a deacidification unit; S20, separating the obtained deacidifying agent and a back-extraction agent in a back-extraction mixing and coalescing unit; S30, conveying the separated upper layer liquid to a back-extraction agent regeneration unit for regeneration; and S40, sending the separated lower layer liquid into the deacidifying agent regeneration unit for regeneration. The deacidification unit includes one or more deacidification mixing and coalescing units, each including a shell. The shell has a premixing zone, a coalescence separation zone, and a sedimentation separation zone arranged from top to bottom. The premixing zone contains structured packing material, and the coalescence separation zone contains polar fiber bundles. The deacidifying agent contains organic amines, a co-solvent, and water. This method can be used for deacidifying high-viscosity and high-acid-value vacuum distillate oils and has a wide range of applications.

Description

Technical Field

[0001] This invention relates to the field of distillate oil refining technology, specifically to a method for deacidifying vacuum distillate oil. Background Technology

[0002] With increasing energy demand and the depletion of conventional low-acid-value crude oil, the demand for high-acid-value crude oil is increasing year by year due to its abundance and relatively low price. However, processing high-acid-value crude oil and its vacuum distillate fractions can cause serious corrosion problems to equipment, affecting the long-term safe operation of refining units. It also results in excessively high acid values ​​in the refined products, impacting their usability. Furthermore, naphthenic acids, the main acidic substances in distillate oils, are important fine chemical raw materials with high application value and wide range of uses. For example, naphthenic acids and their derivatives (metal esters and salts, naphthenates) can be used industrially as lubricants, emulsifiers, paint dryers, oxidation catalysts, and wood preservatives.

[0003] Traditional methods for processing high-acid-value vacuum distillate oils often involve alkali refining or blending with low-acid-value distillate oils to reduce the acid value. The former consumes large amounts of acid and alkali, leading to severe oil-water emulsification, generating significant amounts of waste liquid and alkali residue that pollute the environment and cause equipment corrosion. The latter, while lowering the oil's acid value, still leaves naphthenic acids in the distillate oil, which can still corrode equipment at higher temperatures, failing to address the root cause of the problem. Therefore, developing a clean, environmentally friendly, economical, efficient, simple, and universally applicable deacidification process for high-acid-value vacuum distillate oils is of paramount importance.

[0004] In recent years, various processes for removing naphthenic acids from distillate oils have been developed both domestically and internationally. For example, US5891325 discloses a method for thermal decomposition and deacidification at high temperatures, which can thermally decompose naphthenic acids into alkanes and carbon dioxide, thereby reducing the acid value of the oil. However, this method requires high temperatures, consumes a lot of energy, and is prone to causing the decomposition of other components in the distillate oil, resulting in a decrease in oil yield. In addition, the structure of naphthenic acids is destroyed, making them unrecoverable. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the prior art and provide a clean, environmentally friendly, economical, efficient and simple deacidification method for vacuum distillate oil. This method can not only achieve deacidification of oils with high acid value and high viscosity, but also avoid the loss of deacidifying agent and environmental pollution caused by the mutual entrainment or emulsification of deacidifying agent and vacuum distillate oil. In addition, it can recover naphthenic acids with high application value.

[0006] To achieve the above objectives, the present invention provides a method for deacidifying vacuum distillate oil, the method comprising the following steps:

[0007] S10. Deacidify the vacuum distillate oil and the deacidifying agent in the deacidification unit to obtain the deacidifying agent to be produced and the deacidified vacuum distillate oil after treatment, respectively.

[0008] S20. The deacidifying agent to be produced and the back-extraction agent are extracted and separated in a back-extraction mixing and coalescing device;

[0009] S30. The upper liquid separated from the back-extraction mixing coalescer is transported to the back-extractant regeneration device for regeneration treatment to obtain regenerated back-extractant;

[0010] S40. The lower layer liquid separated in the back-extraction mixing and coalescing device is transported to the deacidifying agent regeneration device for regeneration treatment to obtain naphthenic acid and regenerated deacidifying agent respectively.

[0011] The deacidification unit includes one or more deacidification mixing and coalescing units, and each of the deacidification mixing and coalescing units and the back-extraction mixing and coalescing unit includes a shell. The shell is provided with a premixing zone, a coalescing separation zone and a sedimentation separation zone from top to bottom. The premixing zone is provided with structured packing, the coalescing separation zone is provided with polar fiber bundles, the top of the premixing zone is provided with a liquid inlet, and the side and bottom of the sedimentation separation zone are respectively provided with an upper liquid outlet and a lower liquid outlet.

[0012] The deacidifying agent contains an organic amine, a co-solvent, and water. The organic amine is selected from at least one of diethylamine, triethylamine, ethylenediamine, n-propylamine, n-butylamine, and N,N-dimethylethanolamine. The co-solvent is selected from at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol.

[0013] Preferably, the deacidification unit includes three deacidification mixing and coalescing units, which are respectively a primary deacidification mixing and coalescing unit, a secondary deacidification mixing and coalescing unit, and a tertiary deacidification mixing and coalescing unit along the material flow direction of the vacuum distillate oil. The lower liquid outlet of the primary deacidification mixing and coalescing unit is connected to the liquid inlet of the secondary deacidification mixing and coalescing unit, and the lower liquid outlet of the secondary deacidification mixing and coalescing unit is connected to the liquid inlet of the tertiary deacidification mixing and coalescing unit.

[0014] Preferably, the deacidifying agent fed to the primary deacidification mixing and coalescing device contains diethylamine, isopropanol, and water.

[0015] The deacidifying agent supplied to the secondary deacidification mixing and coalescing unit contains diethylamine, isopropanol, and water.

[0016] The deacidifying agent supplied to the three-stage deacidification mixing and coalescing unit contains ethylenediamine, n-propanol and water.

[0017] Preferably, the total deacidifying agent added to the three deacidifying mixing coalescers has a volume ratio of 1:1 to 1:10 with the vacuum distillate oil.

[0018] Preferably, based on the total volume of the deacidifying agent, the volume fraction of the organic amine is 5%-25%, the volume fraction of the cosolvent is 50%-80%, and the volume fraction of the water is 5%-40%.

[0019] Preferably, in step S20, the back-extraction agent is selected from at least one of D30 solvent oil, D40 solvent oil, D60 solvent oil, D80 solvent oil and D100 solvent oil.

[0020] Preferably, in step S30, the temperature of the regeneration process is 150-250 °C.

[0021] Preferably, in step S40, the temperature of the regeneration process is 120-150 °C.

[0022] Preferably, the polar fiber bundle is made of at least one of hydrophilic modified polyacrylonitrile fiber, hydrophilic modified stainless steel fiber, and hydrophilic modified polylactic acid fiber.

[0023] Preferably, the water contact angle of the polar fiber bundle is 10°-65°.

[0024] Preferably, each polar fiber bundle has a length of 1000-3000 mm and a diameter of 1-200 micrometers.

[0025] Preferably, in the deacidification mixing coalescer and the back-extraction mixing coalescer, the structured packing is selected from at least one of structured packing 125Y, structured packing 250Y, structured packing 350Y, structured packing 450Y, structured packing 500Y and structured packing 700Y.

[0026] Preferably, in the deacidification mixing coalescer and the back-extraction mixing coalescer, the lower liquid outlet is connected to a bend, and the bend is located below the upper liquid outlet.

[0027] Preferably, the method further includes: returning the regenerated back-extractant to the back-extractant mixing coalescer for recycling.

[0028] Preferably, the method further includes: returning the regenerated deacidifying agent to the deacidification unit for recycling.

[0029] The technical solution provided by this invention achieves efficient deacidification through the design of the deacidifying agent's composition. By using a deacidification mixing and coalescing device filled with polar fiber bundles to deacidify vacuum distillate oil, the deacidification effect is further improved while avoiding deacidifying agent loss and environmental pollution caused by entrainment or emulsification between the deacidifying agent and the vacuum distillate oil. This results in high-quality vacuum distillate oil, high recovery rate and purity of the regenerated deacidifying agent, and eliminates the need for downstream settling or washing equipment, saving investment and floor space. Compared to conventional alkaline washing deacidification and settling tank separation, conventional... In the method described in this invention, the liquid flows rapidly (0.5-2 m / s) in the fiber bundle, resulting in advantages such as large processing capacity and high efficiency. The treated distillate oil and the deacidifying agent can be rapidly coalesced and separated in the mixing coalescer and continuously discharged. By using a back-extraction mixing coalescer to extract and separate the deacidifying agent (containing naphthenic acid amine salt and deacidifying agent), the separation effect is good, improving the purity of the recovered naphthenic acid and the quality of the regenerated back-extracting agent and deacidifying agent. This allows the back-extracting agent and deacidifying agent to be recovered and recycled with low energy consumption and high efficiency.

[0030] Therefore, the method described in this invention has a good deacidification effect and can achieve deacidification treatment of vacuum distillate oil with high viscosity and high acid value. It can be used for deacidification treatment of vacuum distillate oil with different viscosity and acid value, with a wide range of applications. Moreover, the whole process is simple to operate, mild, green and environmentally friendly. The back-extraction agent and deacidifying agent can be recycled, and naphthenic acid can be recovered and reused, showing broad application prospects. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of one embodiment of a vacuum distillate oil deacidification system for implementing the vacuum distillate oil deacidification method provided by the present invention.

[0032] Figure 2 yes Figure 1 A schematic diagram of the deacidification and mixing coalescing device.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1. Deacidifying agent supply device; 2. Feed pump; 3. Primary deacidifying agent mixing and coalescing device; 4. Secondary deacidifying agent mixing and coalescing device; 5. Tertiary deacidifying agent mixing and coalescing device; 6. Deacidifying agent storage device; 7. Back-extraction mixing and coalescing device; 8. First heat exchanger; 9. Back-extraction agent regeneration device; 10. First condenser; 11. Second heat exchanger; 12. Deacidifying agent regeneration device; 13. Second condenser;

[0035] 20. Shell; 201. Premixing zone; 202. Coagulation and separation zone; 203. Sedimentation and separation zone; 21. Structured packing; 22. Polar fiber bundle; 23. Mounting plate; 24. Bend; 25. Baffle. Detailed Implementation

[0036] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0037] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0038] This invention provides a method for deacidifying vacuum distillate oil, the method comprising the following steps:

[0039] S10. Deacidify the vacuum distillate oil and the deacidifying agent in the deacidification unit to obtain the deacidifying agent to be produced and the deacidified vacuum distillate oil after treatment, respectively.

[0040] S20. The deacidifying agent to be produced and the back-extraction agent are extracted and separated in the back-extraction mixing and coalescing device 7;

[0041] S30. The upper liquid separated in the back-extraction mixing and coalescing device 7 is transported to the back-extractant regeneration device 9 for regeneration treatment to obtain regenerated back-extractant.

[0042] S40. The lower liquid separated in the back-extraction mixing and coalescing device 7 is transported to the deacidifying agent regeneration device 12 for regeneration treatment to obtain naphthenic acid and regenerated deacidifying agent respectively.

[0043] The deacidification unit includes one or more deacidification mixing and coalescing devices, and each of the deacidification mixing and coalescing devices and the back-extraction mixing and coalescing device 7 includes a shell 20. The shell 20 is provided with a premixing zone 201, a coalescing separation zone 202 and a sedimentation separation zone 203 from top to bottom. The premixing zone 201 is provided with a structured packing 21, the coalescing separation zone 202 is provided with a polar fiber bundle 22, the top of the premixing zone 201 is provided with a liquid inlet, and the side and bottom of the sedimentation separation zone 203 are respectively provided with an upper liquid outlet and a lower liquid outlet.

[0044] The deacidifying agent contains an organic amine, a co-solvent, and water. The organic amine is selected from at least one of diethylamine, triethylamine, ethylenediamine, n-propylamine, n-butylamine, and N,N-dimethylethanolamine. The co-solvent is selected from at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol.

[0045] The method described in this invention is used to remove naphthenic acids from vacuum distillate oil. The vacuum distillate oil to be deacidified can be various distillate oils obtained by vacuum distillation, such as second-line vacuum distillate oil, third-line vacuum distillate oil, etc.

[0046] The higher the viscosity or acid value of the vacuum distillate oil to be treated, the more difficult it is to remove the acid. In the method described in this invention, the deacidifying agent is compounded with the aforementioned organic amine, co-solvent, and water, enabling the deacidifying agent to efficiently remove naphthenic acids from the vacuum distillate oil under mild conditions. Meanwhile, conventional oil deacidification methods involve mixing the deacidifying agent with the oil to be treated, followed by settling in a settling tank or separating funnel to allow for stratification. This method results in poor mixing of the deacidifying agent and the oil, and easy entrainment, leading to poor deacidification. However, in the method described in this invention, a structured packing material is used... The deacidifying mixing and coalescing device 21 and polar fiber bundles 22 are pre-mixed with the structured packing 21. The polar fiber bundles 22 increase the contact area between the deacidifying agent and the vacuum distillate oil, enhance coalescence separation, and achieve efficient deacidification. This avoids the loss of deacidifying agent and environmental pollution caused by mutual entrainment or emulsification between the deacidifying agent and the vacuum distillate oil, further improving the deacidification effect. In addition, by using the back-extraction mixing and coalescing device 7 to extract and separate the deacidifying agent to be produced, a small amount of vacuum distillate oil dissolved in the deacidifying agent to be produced is removed, improving the purity of the recovered naphthenic acid and the purity and recovery rate of the regenerated back-extractant and deacidifying agent. Therefore, the method described in this invention can achieve effective deacidification of high viscosity and high acid value vacuum distillate oil, and the back-extractant and deacidifying agent can be recovered and recycled with low energy consumption and high efficiency. Naphthenic acid can be recycled, showing broad application prospects.

[0047] In this invention, the vacuum distillate oil deacidification method is carried out in a vacuum distillate oil deacidification system. Please refer to the relevant documentation. Figure 1 and Figure 2 The system includes a deacidifying agent supply device 1, a deacidification unit, a back-extraction mixing and coalescing device 7, a back-extraction agent regeneration device 9, and a deacidifying agent regeneration device 12. Specifically, the deacidifying agent supply device 1 is connected to the inlet of the deacidification unit, the upper liquid outlet of the deacidification unit is connected to the inlet of the back-extraction mixing and coalescing device 7, the upper liquid outlet of the back-extraction mixing and coalescing device 7 is connected to the back-extraction agent regeneration device 9, and the lower liquid outlet of the back-extraction mixing and coalescing device 7 is connected to the deacidifying agent regeneration device 12.

[0048] In one specific embodiment, the back-extractant regeneration device 9 and the deacidifying agent regeneration device 12 have the same structure, both being conventional regeneration towers in the art.

[0049] In the method described in this invention, the deacidifying agent is obtained by compounding the above-mentioned specifically selected organic amine with low molecular weight alcohol and water. The deacidifying agent of the above components has the following advantages: 1. The synergistic effect of organic amine, low molecular weight alcohol and water enhances the deacidification effect of vacuum distillate oil, and the organic amine and low molecular weight alcohol are easy to recover and recycle; the organic amine undergoes a neutralization reaction with naphthenic acid to generate amine salt. This reaction process is mild, does not require harsh reaction conditions, and the reaction products are easy to separate. At the same time, the organic amine will not introduce other impurities or adversely affect other properties of the oil, thus ensuring the quality of the oil. 1. Quantity; 2. Compared with the traditional alkaline washing deacidification process, the synergistic deacidification of organic amines, low molecular weight alcohols and water does not use highly corrosive alkaline solutions, reducing equipment corrosion and lowering equipment maintenance costs; it is less likely to cause emulsification, avoiding oil loss and subsequent processing difficulties caused by emulsification; 3. The synergistic effect of organic amines, low molecular weight alcohols and water in removing naphthenic acids usually operates at temperatures ranging from room temperature to lower temperatures, reducing energy consumption compared with the traditional high temperature and high pressure deacidification process; 4. The raw materials for the synthesis of organic amines and low molecular weight alcohols are widely available and the synthesis process is mature.

[0050] In a preferred embodiment, based on the total volume of the deacidifying agent, the volume fraction of the organic amine is 5%-25%, the volume fraction of the co-solvent is 50%-80%, and the volume fraction of water is 5%-40%. By using the deacidifying agent with the above-mentioned proportions, its deacidification effect is better.

[0051] More preferably, based on the total volume of the deacidifying agent, the volume fraction of the organic amine is 5%-15%, the volume fraction of the co-solvent is 60%-80%, and the volume fraction of the water is 15%-25%.

[0052] This invention does not limit the number of deacidification mixing and coalescing devices in the deacidification unit; it can be one, two, three, four, etc. In a preferred embodiment, the deacidification unit includes three deacidification mixing and coalescing devices, which are respectively a primary deacidification mixing and coalescing device 3, a secondary deacidification mixing and coalescing device 4, and a tertiary deacidification mixing and coalescing device 5 along the material flow direction of the vacuum distillate oil. The lower liquid outlet of the primary deacidification mixing and coalescing device 3 is connected to the liquid inlet of the secondary deacidification mixing and coalescing device 4, and the lower liquid outlet of the secondary deacidification mixing and coalescing device 4 is connected to the liquid inlet of the tertiary deacidification mixing and coalescing device 5.

[0053] In practice, the deacidifying agent and vacuum distillate oil undergo reaction extraction and deacidification in the primary deacidification mixing and coalescing unit 3. The resulting lower liquid (deacidified distillate oil) is then sequentially passed through the secondary deacidification mixing and coalescing unit 4 and the tertiary deacidification mixing and coalescing unit 5, where it undergoes step-by-step reaction extraction and deacidification with added fresh deacidifying agent. Refined vacuum distillate oil is obtained in the lower layer of the tertiary deacidification mixing and coalescing unit 5. By subjecting the vacuum distillate oil to tertiary deacidification treatment, the deacidification effect of the vacuum distillate oil can be significantly improved, and the consumption of deacidifying agent is low. In this embodiment, the upper liquid (deacidifying agent to be produced) obtained from the primary deacidification mixing and coalescing unit 3, the secondary deacidification mixing and coalescing unit 4, and the tertiary deacidification mixing and coalescing unit 5 are all transported to the back-extraction mixing and coalescing unit 7 for further processing.

[0054] In some embodiments, the deacidifying agent components in the primary deacidification mixing and coalescing device 3, the secondary deacidification mixing and coalescing device 4, and the tertiary deacidification mixing and coalescing device 5 are the same, thus simplifying operation and reducing costs.

[0055] In this embodiment, the deacidifying agent supply device 1 is connected to the primary deacidifying mixing and coalescing device 3, the secondary deacidifying mixing and coalescing device 4, and the tertiary deacidifying mixing and coalescing device 5 via a feed pump 2, and is used to supply deacidifying agents of the same composition to the primary deacidifying mixing and coalescing device 3, the secondary deacidifying mixing and coalescing device 4, and the tertiary deacidifying mixing and coalescing device 5. In this embodiment, the deacidifying agents to be processed obtained from the primary deacidifying mixing and coalescing device 3, the secondary deacidifying mixing and coalescing device 4, and the tertiary deacidifying mixing and coalescing device 5 are first centrally transported to the deacidifying agent storage device 6, and then transported to the back-extraction mixing and coalescing device 7 for processing. Specifically, the upper liquid outlets of the primary deacidifying mixing and coalescing device 3, the secondary deacidifying mixing and coalescing device 4, and the tertiary deacidifying mixing and coalescing device 5 are all connected to the liquid inlet of the deacidifying agent storage device 6, and the outlet of the deacidifying agent storage device 6 is connected to the inlet of the back-extraction mixing and coalescing device 7.

[0056] In other embodiments, the deacidifying agents in the primary deacidification mixing and coalescing unit 3, the secondary deacidification mixing and coalescing unit 4, and the tertiary deacidification mixing and coalescing unit 5 have different compositions. Preferably, the deacidifying agent supplied to the primary deacidification mixing and coalescing unit 3 contains diethylamine, isopropanol, and water; the deacidifying agent supplied to the secondary deacidification mixing and coalescing unit 4 contains diethylamine, isopropanol, and water; and the deacidifying agent supplied to the tertiary deacidification mixing and coalescing unit 5 contains ethylenediamine, n-propanol, and water. By sequentially treating the vacuum distillate oil to be deacidified with the above-mentioned deacidifying agents, when the acid value of the distillate oil is high, the first two stages of the deacidification mixing and coalescing device use diethylamine and isopropanol, which have moderate polarity and relatively low boiling point, to remove most of the naphthenic acids in the distillate oil. The third stage of the deacidification mixing and coalescing device uses ethylenediamine and n-propanol, which have strong polarity and relatively high boiling point, to remove the remaining naphthenic acids in the distillate oil at a deeper level. This not only effectively deacidifies the distillate oil but also facilitates the centralized recovery and recycling of the deacidifying agents, and saves energy.

[0057] In this embodiment, there are two deacidifying agent supply devices 1. One deacidifying agent supply device 1 is connected to the first-stage deacidifying mixing and coalescing device 3 and the second-stage deacidifying mixing and coalescing device 4 respectively, so as to supply deacidifying agent of the same composition to the first-stage deacidifying mixing and coalescing device 3 and the second-stage deacidifying mixing and coalescing device 4. The other deacidifying agent supply device 1 is connected to the third-stage deacidifying mixing and coalescing device 5 respectively, so as to provide deacidifying agent of different composition to the third-stage deacidifying mixing and coalescing device 5.

[0058] Preferably, in this embodiment, the number of the deacidifying agent storage device 6, the back-extraction mixing and coalescing device 7, and the deacidifying agent regeneration device 12 is also two. Specifically, one of the two back-extraction mixing and coalescing devices 7 is connected to the primary deacidifying mixing and coalescing device 3 and the secondary deacidifying mixing and coalescing device 4, and the other is connected to the tertiary deacidifying mixing and coalescing device 5; one of the two deacidifying agent regeneration devices 12 is correspondingly connected to the primary deacidifying mixing and coalescing device 3 and the secondary deacidifying mixing and coalescing device 4, and the other is correspondingly connected to the tertiary deacidifying mixing and coalescing device 5; one of the two deacidifying agent storage devices 6 is connected to the primary deacidifying mixing and coalescing device 3 and the secondary deacidifying mixing and coalescing device 4, and the other is connected to the tertiary deacidifying mixing and coalescing device 5.

[0059] In one specific embodiment, the deacidifying agent supply device 1 and the deacidifying agent storage device 6 have the same structure, both being conventional storage tanks in the art.

[0060] In this invention, the amount of deacidifying agent used in the primary deacidification mixing and coalescing unit, the secondary deacidification mixing and coalescing unit, and the tertiary deacidification mixing and coalescing unit can be the same or different, and can be adjusted according to actual conditions. In a preferred embodiment, the total deacidifying agent added to the three deacidification mixing and coalescing units (primary deacidification mixing and coalescing unit 3, secondary deacidification mixing and coalescing unit 4, and tertiary deacidification mixing and coalescing unit 5) has a volume ratio of 1:1 to 1:10 of vacuum distillate oil. More preferably, the amount of deacidifying agent used in the primary deacidification mixing and coalescing unit 3, the secondary deacidification mixing and coalescing unit 4, and the tertiary deacidification mixing and coalescing unit 5 is the same.

[0061] In a preferred embodiment, in step S20, the back-extraction agent is selected from at least one of D30 solvent oil, D40 solvent oil, D60 solvent oil, D80 solvent oil, and D100 solvent oil.

[0062] In some embodiments, in step S30, the temperature of the regeneration process is 150-250 °C. By maintaining the back-extractant regeneration device 9 within the above temperature range, the upper liquid separated in the back-extraction mixing coalescer 7 is regenerated. The bottom of the back-extractant regeneration device 9 is obtained as refined vacuum distillate oil (i.e., deacidified vacuum distillate oil), and the top of the column is obtained as regenerated back-extractant. The back-extractant is of high quality and can be returned to the back-extraction mixing coalescer 7 for multiple cycles.

[0063] In some embodiments, the method further includes returning the regenerated back-extractant to the back-extraction mixing coalescer 7 for recycling.

[0064] In some embodiments, the upper liquid from the back-extraction mixing coalescer 7 is heated in the first heat exchanger 8 before entering the back-extractant regeneration device 9.

[0065] In one specific embodiment, step S30 includes: the upper liquid from the back-extraction mixing coalescer 7 enters the first heat exchanger 8 for heating treatment, and then enters the back-extraction agent regeneration device 9 for regeneration treatment. Refined vacuum distillate oil is obtained at the bottom of the column, and the vapor at the top of the column is condensed to obtain the regenerated back-extraction agent. The regenerated back-extraction agent is returned to the back-extraction mixing coalescer 7 for recycling.

[0066] In some embodiments, in step S40, the temperature of the regeneration process is 120-150 °C. The lower liquid separated in the back-extraction mixing and coalescing unit 7 is regenerated by maintaining the deacidifying agent regeneration device 12 at the above temperature range. The regenerated deacidifying agent is obtained at the top of the deacidifying agent regeneration device 12, and naphthenic acid is recovered at the bottom of the tower. The regenerated deacidifying agent has high purity and can be returned to the deacidification unit for multiple cycles of use.

[0067] In some embodiments, the method further includes returning the regenerated deacidifying agent to the deacidification unit for recycling.

[0068] In some embodiments, the lower layer liquid from the back-extraction mixing coalescer 7 is heated in the second heat exchanger 11 before entering the deacidifying agent regeneration device 12.

[0069] In one specific embodiment, step S40 includes: the lower layer liquid from the back-extraction mixing coalescer 7 enters the second heat exchanger 11 for heating, and then enters the deacidifying agent regeneration device 12 for regeneration treatment. Naphthenic acid is obtained at the bottom of the column, and the vapor at the top of the column is condensed to obtain the regenerated deacidifying agent. The regenerated deacidifying agent is returned to the deacidification unit for recycling.

[0070] In the method described in this invention, the regeneration processes in steps S30 and S40 can be carried out under normal pressure conditions.

[0071] In this invention, each of the deacidification mixing and coalescing devices includes a shell, which is provided with a premixing zone 201, a coalescing separation zone 202, and a settling separation zone 203 from top to bottom. In specific implementation, the vacuum distillate oil to be treated enters the deacidification mixing and coalescing device, first entering the premixing zone 201, where it is mixed with the deacidifying agent by the structured packing 21 and evenly distributed, and then enters the coalescing separation zone 202, where it contacts and reacts with the filled polar fiber bundles. Then, it separates into layers in the settling separation zone 203, resulting in the deacidifying agent in the upper layer and the deacidified vacuum distillate oil in the lower layer.

[0072] Specifically, the working principle and process of the coalescence separation zone 202 and the sedimentation separation zone 203 in each of the aforementioned deacidification mixing coalescers are as follows: The two immiscible liquids exhibit different surface tensions on the fiber bundle surface. When the vacuum distillate oil and the polar deacidifying agent flow downwards along the polar fiber bundle 22, the deacidifying agent adheres to the fiber surface and is stretched into an extremely thin film, thereby expanding small-volume droplets into a large-area liquid film. The vacuum distillate oil rubs against the deacidifying agent attached to the fiber bundle, causing the surface of the deacidifying agent liquid film attached to the fiber bundle surface to continuously form a wave-like pattern. The increased contact area and faster interface renewal rate result in a more complete reaction, significantly improving deacidification efficiency. Furthermore, after the deacidifying agent and vacuum distillate oil complete their contact reaction, a phase separation process occurs. At this point, the vacuum distillate oil separates from the bottom of the fiber bundle, while the deacidifying agent, due to strong surface tension, remains adsorbed on the fiber surface and continues to flow downwards to the settling separation zone 203, where it detaches and forms large particles that quickly settle. Moreover, the oil and water phases have different densities; therefore, the deacidified distillate oil and the deacidifying agent quickly form a two-liquid interface within the separation tank. This clean separation method ensures that the deacidified vacuum distillate oil and the deacidifying agent do not form or minimally form entrainment between them.

[0073] In this invention, the deacidification mixing coalescer and the extraction mixing coalescer have the same structure, only the processing objects are different. Therefore, the working principles of the extraction mixing coalescer and the deacidification mixing coalescer are basically the same, and will not be described in detail here.

[0074] In this invention, in the deacidification mixing and coalescing device and the extraction mixing and coalescing device, the upper liquid outlet of the sedimentation separation zone 203 is located on the side of the sedimentation separation zone 203, and the lower liquid outlet of the sedimentation separation zone 203 is located at the bottom of the sedimentation separation zone 203. Further, the lower liquid outlet is connected to a bend 24, which is located below the upper liquid outlet (i.e., the height of the bend is lower than the upper liquid outlet of the sedimentation separation zone 203). Through this design, when the liquid level in the sedimentation separation zone 203 reaches the upper liquid outlet, the upper liquid in the sedimentation separation zone 203 is automatically discharged through the upper liquid outlet; when the liquid level in the sedimentation separation zone 203 exceeds the height of the upper part of the bend, the lower liquid in the sedimentation separation zone 203 is automatically discharged through the lower liquid outlet, thereby achieving continuous discharge of the upper and lower liquids from the sedimentation separation zone 203.

[0075] In one specific embodiment, the bend is a U-shaped bend.

[0076] In some embodiments, the temperature of the deacidification treatment in step S10 is 20-50 °C. Specifically, the temperature of the deacidification mixing and coalescing device is maintained at 20-50 °C.

[0077] In the method described in this invention, in step S20, the extraction and separation can be carried out at room temperature (21-28°C).

[0078] In a preferred embodiment, in the deacidification mixing coalescer and the back-extraction mixing coalescer 7, the polar fiber bundle 22 is made of at least one of hydrophilic modified polyacrylonitrile fiber, hydrophilic modified stainless steel fiber, and hydrophilic modified polylactic acid fiber, more preferably hydrophilic modified stainless steel fiber. By selecting the above-mentioned materials for the polar fiber bundle 22, its deacidification effect on vacuum distillate oil is better. The hydrophilic modified fiber bundle can be purchased directly or prepared in-house. When prepared in-house, conventional hydrophilic modification methods in the art can be used, such as laser polishing, plasma treatment, ultraviolet radiation treatment, surface grafting treatment, and chemical etching.

[0079] In a preferred embodiment, in the deacidification mixing coalescer and the back-extraction mixing coalescer 7, each polar fiber bundle 22 has a length of 1000-3000 mm and a diameter of 1-200 micrometers, thus achieving good deacidification effect and low cost.

[0080] In a preferred embodiment, the water contact angle of the polar fiber bundle 22 is 10°-65°.

[0081] In some embodiments, the polar fiber bundle 22 extends into the sedimentation separation zone 203, and the lower end of the polar fiber bundle 22 is located above the upper edge of the upper liquid outlet.

[0082] In a preferred embodiment, the polar fiber bundle 22 is suspended below the structured packing 21, and the polar fiber bundle 22 completely fills the shell 20 (filling area is 95-100%). In this way, the vacuum distillate oil can better contact the polar fiber bundle 22, thereby improving the deacidification effect.

[0083] In a specific implementation, the lower surface of the premixed zone 201 is provided with a mounting plate 23, and the mounting plate 23 has several holes, and the polar fiber bundle 22 is suspended on the lower surface of the mounting plate.

[0084] In some embodiments, in the deacidification mixing coalescer and the back-extraction mixing coalescer 7, the longitudinal cross-sectional area of ​​the sedimentation separation zone 203 is greater than the longitudinal cross-sectional area of ​​the coalescence separation zone 202.

[0085] In some embodiments, in the deacidification mixing and coalescing device and the back-extraction mixing and coalescing device 7, a baffle 25 is suspended on the upper surface of the sedimentation separation zone 203, and the baffle 25 is close to the outlet of the upper liquid. The deacidification effect is improved by setting the baffle 25.

[0086] In this invention, the premixing zone 201 in the deacidification mixing and coalescing unit and the back-extraction mixing and coalescing unit 7 is filled with structured packing material 21, thereby making the mixing of materials more thorough. In some embodiments, the structured packing material 21 is selected from at least one of structured packing material 125Y, structured packing material 250Y, structured packing material 350Y, structured packing material 450Y, structured packing material 500Y, and structured packing material 700Y, preferably structured packing material 250Y.

[0087] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited thereto. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available products.

[0088] In the following examples, room temperature refers to 23±2℃.

[0089] In the following embodiments, the hydrophilic modified stainless steel fiber bundles used are modified by laser roughening, and the water contact angle of the hydrophilic modified stainless steel fiber bundles is 30-40°.

[0090] In the following embodiments, the testing methods involved include:

[0091] The acid value and basic nitrogen content of the oil sample were tested using a titrator.

[0092] The viscosity of the oil sample was tested using a fully automated viscometer.

[0093] The structure of cycloalkanoic acid was analyzed using Fourier transform infrared spectroscopy.

[0094] Example 1

[0095] The vacuum distillate oil to be processed originated from a refinery, with an initial acid value (based on KOH, the same below) of 4.52 mg / g and a viscosity (20℃) of 688.86 mm. 2 / s.

[0096] This embodiment refers to Figure 1 The system shown includes a deacidifying agent supply device 1, a deacidification unit, a deacidifying agent storage device 6, a back-extraction mixing and coalescing device 7, a first heat exchanger 8, a back-extraction agent regeneration device 9 (back-extraction agent regeneration tower), a first condenser 10, a second heat exchanger 11, a deacidifying agent regeneration device 12 (deacidifying agent regeneration tower), and a second condenser 13. The deacidification unit includes three deacidifying mixing and coalescing devices, which are a primary deacidifying mixing and coalescing device 3, a secondary deacidifying mixing and coalescing device 4, and a tertiary deacidifying mixing and coalescing device 5, respectively, along the material flow direction of the vacuum distillate oil.

[0097] The structure of each of the aforementioned deacidification mixing and coalescing devices (primary deacidification mixing and coalescing device 3, secondary deacidification mixing and coalescing device 4, and tertiary deacidification mixing and coalescing device 5) is as follows: Figure 2 As shown, it includes a shell 20, which, from top to bottom, is provided with a premixing zone 201, a coalescence separation zone 202, and a settling separation zone 203. The premixing zone 201 is filled with structured packing 21 (structured packing 250Y). The coalescence separation zone 202 is filled with polar fiber bundles 22, which extend into the settling separation zone 203. The polar fiber bundles 22 are made of hydrophilically modified stainless steel fibers. The length of the polar fiber bundles 22 is 2000 mm. The premixing zone 201 has a liquid inlet at the top and a diameter of 50 micrometers. The sedimentation separation zone 203 has an upper liquid outlet on its side and a lower liquid outlet at its bottom, with the upper liquid outlet being lower than the lower end of the polar fiber bundle 22. A baffle 25 is suspended on the upper surface of the sedimentation separation zone 203, and the baffle 25 is close to the upper liquid outlet. The lower liquid outlet is connected to a bend 24, and the height of the bend 24 is lower than that of the upper liquid outlet.

[0098] The structure of the back-extraction mixed coalescer 7 is the same as that of the deacidification mixed coalescer;

[0099] The deacidifying agent supply device 1 is connected to the primary deacidifying mixing and coalescing device 3, the secondary deacidifying mixing and coalescing device 4, and the tertiary deacidifying mixing and coalescing device 5 via the feed pump 2. The lower liquid outlet of the primary deacidifying mixing and coalescing device 3 is connected to the liquid inlet of the secondary deacidifying mixing and coalescing device 4, and the lower liquid outlet of the secondary deacidifying mixing and coalescing device 4 is connected to the liquid inlet of the tertiary deacidifying mixing and coalescing device 5. The upper liquid outlets of the primary deacidifying mixing and coalescing device 3, the secondary deacidifying mixing and coalescing device 4, and the tertiary deacidifying mixing and coalescing device 5 are connected to the deacidifying agent storage device 6, and the deacidifying agent storage device 6 is connected to the inlet of the back-extraction mixing and coalescing device 7.

[0100] The upper liquid outlet of the back-extraction mixing and coalescing unit 7 is connected in sequence to the first heat exchanger 8 and the back-extractant regeneration device 9. The top outlet of the back-extractant regeneration device 9 is connected to the first condenser 10. The lower liquid outlet of the back-extractant is connected in sequence to the second heat exchanger 11 and the deacidifying agent regeneration device 12. The top outlet of the deacidifying agent regeneration device 12 is connected to the second condenser 13.

[0101] The deacidifying agent used contains the following components by volume fraction: 10% diethylamine, 70% n-propanol and 20% water; D60 solvent oil is selected as the back-extraction agent.

[0102] The deacidification method for vacuum distillate oil includes the following steps:

[0103] (1) Fresh deacidifying agent from deacidifying agent supply device 1 and vacuum distillate oil to be treated are respectively fed into primary deacidifying mixing and coalescing unit 3 for mixing, reaction and separation. The volume of fresh deacidifying agent added to secondary deacidifying mixing and coalescing unit 4 and tertiary deacidifying mixing and coalescing unit 5 is the same as that added to primary deacidifying mixing and coalescing unit 3. The ratio of the total volume of deacidifying agent added to primary deacidifying mixing and coalescing unit 3, secondary deacidifying mixing and coalescing unit 4 and tertiary deacidifying mixing and coalescing unit 5 to the volume of vacuum distillate oil is 3:4. The reaction and separation temperature of each stage of deacidifying mixing and coalescing unit (primary deacidifying mixing and coalescing unit 3, secondary deacidifying mixing and coalescing unit 4 and tertiary deacidifying mixing and coalescing unit 5) is 30°C. ℃; The lower layer liquid of the first-stage deacidification mixing and coalescing unit 3 is processed sequentially by the second-stage deacidification mixing and coalescing unit 4 and the third-stage deacidification mixing and coalescing unit 5. Refined vacuum distillate oil is obtained at the lower layer liquid outlet of the third-stage deacidification mixer. The deacidifying agent to be generated at the upper layer liquid outlet of each stage deacidification mixing and coalescing unit is first collected into the deacidifying agent storage device 6.

[0104] (2) The back-extractant and the deacidifying agent from the deacidifying agent storage device 6 are respectively fed into the back-extraction mixing and coalescing device 7 for mixing and back-extraction separation at room temperature;

[0105] (3) The upper liquid of the back-extraction mixing coalescer 7 is heated by the first heat exchanger 8 and then sent to the back-extraction agent regeneration tower for regeneration at 180 °C. The top vapor of the tower is condensed by the first condenser 10 to obtain the regenerated back-extraction agent, and the bottom of the tower is refined vacuum distillate oil.

[0106] (4) The lower liquid of the back-extraction mixing coalescer 7 is heated by the second heat exchanger 11 and then sent to the deacidifying agent regeneration tower for regeneration at 140 °C. The top steam of the tower is condensed by the second condenser 13 to obtain the regenerated deacidifying agent, and the naphthenic acid is recovered at the bottom of the tower.

[0107] The results of the tests on the refined vacuum distillate oil at the outlet of the refined vacuum distillate oil, the naphthenic acid at the outlet of the naphthenic acid, and the regenerated deacidifying agent at the outlet of the second condenser 13 are as follows:

[0108] The refined vacuum distillate oil has an acid value of 0.012 mgKOH / g and a deacidification rate of 99.73%, meeting the standard of general lubricating oil base oil PCL 150SN; the organic amines entrained in the refined vacuum distillate oil are less than 5 ppm;

[0109] The recovered naphthenic acid has an acid value of 179.5 mgKOH / g and a purity of 99.5%, meeting the quality standard of grade 55 petroleum acid.

[0110] The regenerated deacidifying agent can be recycled, and the deacidification rate can still reach 99.2% of that of the fresh deacidifying agent.

[0111] Example 2

[0112] The method described in Example 1 was implemented, except that the vacuum distillate oil to be treated was a vacuum third-line distillate oil with a viscosity of 16214 mm (20°C). 2 / s, acid value 3.62 mgKOH / g.

[0113] The experimental results of this embodiment are as follows:

[0114] The experimental results are as follows: the acid value of the deacidified vacuum distillate oil is 0.031 mgKOH / g, and the deacidification rate is 99.14%, which meets the standards of general lubricating oil base oils PCL 400SN and PCL 150BS; the organic amines entrained in the refined vacuum distillate oil are less than 8 ppm;

[0115] The recovered naphthenic acid had an acid value of 157.3 mgKOH / g and a purity of 99.1%.

[0116] The regenerated deacidifying agent can be recycled, and the deacidification rate can still reach 99.4% of that of the fresh deacidifying agent.

[0117] Example 3

[0118] The method described in Example 1 was carried out, except that the vacuum distillate oil to be treated was: second-line vacuum distillate oil with a viscosity of 637.64 mm (at 20°C). 2 / s, acid value 8.01 mgKOH / g.

[0119] The experimental results are as follows: the acid value of the deacidified vacuum distillate oil is 0.019 mgKOH / g, and the deacidification rate is 99.76%; the organic amines entrained in the refined vacuum distillate oil are less than 3 ppm;

[0120] The recovered naphthenic acid has an acid value of 200.6 mgKOH / g and a purity of 99.2%, meeting the quality standard of grade 75 petroleum acid.

[0121] The regenerated deacidifying agent can be recycled, and the deacidification rate can still reach 99.1% of that of the fresh deacidifying agent.

[0122] Example 4

[0123] The method described in Example 1 differs from that described in that the vacuum distillate oil to be treated is a vacuum third-line distillate oil with a viscosity of 15418 mm (at 20°C). 2 / s, acid value 7.52 mgKOH / g.

[0124] The experimental results are as follows: the acid value of the deacidified vacuum distillate oil is 0.096 mgKOH / g, and the deacidification rate is 98.72%; the organic amines entrained in the refined vacuum distillate oil are less than 10 ppm;

[0125] The recovered naphthenic acid has an acid value of 180.8 mgKOH / g and a purity of 97.9%, meeting the quality standard of grade 55 petroleum acid.

[0126] The regenerated deacidifying agent can be recycled, and the deacidification rate can still reach 99.1% of that of the fresh deacidifying agent.

[0127] Example 5

[0128] The method described in Example 4 is implemented, except that there are two deacidifying agent supply devices 1. One device supplies deacidifying agent to the primary deacidifying mixing and coalescing device 3 and the secondary deacidifying mixing and coalescing device 4, and the other device supplies deacidifying agent to the tertiary deacidifying mixing and coalescing device 5. The deacidifying agent supplied to the primary deacidifying mixing and coalescing device 3 contains (by volume fraction): 10% diethylamine, 70% isopropanol and 20% water. The deacidifying agent supplied to the secondary deacidifying mixing and coalescing device 4 contains (by volume fraction): 10% diethylamine, 70% isopropanol and 20% water. The deacidifying agent supplied to the tertiary deacidifying mixing and coalescing device 5 contains (by volume fraction): 10% ethylenediamine, 70% n-propanol and 20% water. There are also two deacidifying agent storage devices 6, two back-extraction mixing and coalescing devices 7, two back-extraction agent regeneration devices 9 and two deacidifying agent regeneration devices 12.

[0129] Vacuum distillate oil to be processed (viscosity: 15418 mm at 20°C) 2 / s, acid value 7.52 mgKOH / g) After the above treatment, the experimental results are as follows:

[0130] The acid value of the deacidified vacuum distillate oil is 0.029 mgKOH / g, and the deacidification rate is 99.61%, meeting the standards of general lubricating oil base oils PCL 400SN and PCL 150BS; the organic amines entrained in the refined vacuum distillate oil are less than 5 ppm;

[0131] The recovered naphthenic acid has an acid value of 185.7 mgKOH / g and a purity of 98.56%, meeting the quality standard of grade 65 petroleum acid.

[0132] The regenerated deacidifying agent can be recycled, and the deacidification rate can still reach 99.4% of that of the fresh deacidifying agent.

[0133] Example 6

[0134] The method described in Example 4 was implemented, except that the deacidifying agent used contained the following components in volume fractions: 10% n-propylamine, 70% n-propanol and 20% water.

[0135] The experimental results are as follows: the acid value of the deacidified vacuum distillate oil is 0.21 mgKOH / g, and the deacidification rate is 97.21%; the organic amines entrained in the refined vacuum distillate oil are less than 30 ppm;

[0136] The recovered naphthenic acid had an acid value of 170.6 mgKOH / g and a purity of 96.3%.

[0137] The regenerated deacidifying agent can be recycled, and the deacidification rate can still reach 98.7% of that of the fresh deacidifying agent.

[0138] Comparative Example 1

[0139] The method described in Example 4 was implemented, except that the three deacidification mixing and coalescing devices (first-stage deacidification mixing and coalescing device 3, second-stage deacidification mixing and coalescing device 4 and third-stage deacidification mixing and coalescing device 5) were replaced with a stirrer and a separatory funnel, respectively, and the separatory funnel was allowed to stand and separate into layers.

[0140] Vacuum distillate oil to be processed (viscosity: 15418 mm at 20°C) 2 / s, acid value 7.52 mgKOH / g) After the above treatment, the experimental results are as follows:

[0141] The acid value of the deacidified vacuum distillate oil is 0.41 mgKOH / g, the deacidification rate is 94.5%, and the organic amines entrained in the refined vacuum distillate oil are greater than 1000 ppm.

[0142] The recovered naphthenic acid had an acid value of 146.8 mgKOH / g and a purity of 80.4%.

[0143] The deacidification effect of recycled deacidifying agent can reach 90.3% of that of fresh deacidifying agent.

[0144] Comparative Example 2

[0145] The method described in Example 4 was implemented, except that the deacidifying agent used contained the following components by volume fraction: 10% ammonia and 90% ethylene glycol.

[0146] Vacuum distillate oil to be processed (viscosity: 15418 mm at 20°C) 2 / s, acid value 7.52 mgKOH / g) After the above treatment, the experimental results are as follows:

[0147] The acid value of the deacidified vacuum distillate oil was 1.24 mgKOH / g, the deacidification rate was 83.51%, and the organic amines entrained in the refined vacuum distillate oil were less than 50 ppm.

[0148] The recovered naphthenic acid had an acid value of 143.6 mgKOH / g and a purity of 79.3%.

[0149] The regenerated deacidifying agent can be recycled, and the deacidification effect can reach 89.2% of that of the fresh deacidifying agent.

[0150] Comparative Example 3

[0151] The method described in Example 4 was implemented, except that the deacidifying agent used contained the following components in volume fractions: 10% cyclohexylamine and 90% glycerol.

[0152] Vacuum distillate oil to be processed (viscosity: 15418 mm at 20°C) 2 / s, acid value 7.52 mgKOH / g) After the above treatment, the experimental results are as follows:

[0153] The acid value of the deacidified vacuum distillate oil was 1.39 mgKOH / g, the deacidification rate was 81.52%, and the organic amines entrained in the refined vacuum distillate oil were less than 20 ppm.

[0154] The recovered naphthenic acid had an acid value of 139.3 mgKOH / g and a purity of 78.1%.

[0155] The regenerated deacidifying agent can be recycled, and the deacidification effect can reach 92.9% of that of the fresh deacidifying agent.

[0156] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for deacidifying vacuum distillate oil, characterized in that, The method includes the following steps: S10. Deacidify the vacuum distillate oil and the deacidifying agent in the deacidification unit to obtain the deacidifying agent to be produced and the deacidified vacuum distillate oil after treatment, respectively. S20. The deacidifying agent to be produced and the back-extraction agent are extracted and separated in a back-extraction mixing and coalescing device (7); S30. The upper liquid separated from the back-extraction mixing coalescer (7) is transported to the back-extractant regeneration device (9) for regeneration treatment to obtain regenerated back-extractant; S40. The lower liquid separated in the back-extraction mixing coalescer (7) is transported to the deacidifying agent regeneration device (12) for regeneration treatment and naphthenic acid and regenerated deacidifying agent are obtained respectively. The deacidification unit includes one or more deacidification mixing and coalescing units, and the deacidification mixing and coalescing unit and the back-extraction mixing and coalescing unit (7) each include a shell (20). The shell (20) is provided with a premixing zone (201), a coalescing separation zone (202), and a sedimentation separation zone (203) from top to bottom. The premixing zone (201) is provided with a structured packing (21), the coalescing separation zone (202) is provided with a polar fiber bundle (22), the top of the premixing zone (201) is provided with a liquid inlet, and the side and bottom of the sedimentation separation zone (203) are respectively provided with an upper liquid outlet and a lower liquid outlet. The deacidifying agent contains an organic amine, a co-solvent, and water. The organic amine is selected from at least one of diethylamine, triethylamine, ethylenediamine, n-propylamine, and n-butylamine. The co-solvent is selected from at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol. Based on the total volume of the deacidifying agent, the volume fraction of the organic amine is 5%-15%, the volume fraction of the co-solvent is 60%-80%, and the volume fraction of water is 15%-25%. The back-extraction agent is selected from at least one of D30 solvent oil, D40 solvent oil, D60 solvent oil, D80 solvent oil, and D100 solvent oil; The polar fiber bundle (22) is made of at least one of hydrophilic modified polyacrylonitrile fiber, hydrophilic modified stainless steel fiber and hydrophilic modified polylactic acid fiber, and the water contact angle of the polar fiber bundle (22) is 10°-65°. In the deacidification mixing coalescer and the back-extraction mixing coalescer (7), the lower liquid outlet is connected to a bend (24), and the bend (24) is located below the upper liquid outlet.

2. The method according to claim 1, characterized in that, The deacidification unit includes three deacidification mixing and coalescing units, which are respectively a primary deacidification mixing and coalescing unit (3), a secondary deacidification mixing and coalescing unit (4), and a tertiary deacidification mixing and coalescing unit (5) along the material flow direction of the vacuum distillate. The lower liquid outlet of the primary deacidification mixing and coalescing unit (3) is connected to the liquid inlet of the secondary deacidification mixing and coalescing unit (4), and the lower liquid outlet of the secondary deacidification mixing and coalescing unit (4) is connected to the liquid inlet of the tertiary deacidification mixing and coalescing unit (5).

3. The method according to claim 2, characterized in that, The deacidifying agent supplied to the primary deacidifying mixing and coalescing unit (3) contains diethylamine, isopropanol, and water. The deacidifying agent supplied to the secondary deacidification mixing and coalescing unit (4) contains diethylamine, isopropanol, and water. The deacidifying agent delivered to the three-stage deacidification mixing and coalescing unit (5) contains ethylenediamine, n-propanol and water.

4. The method according to claim 2 or 3, characterized in that, The total deacidifying agent added to the three deacidifying mixing coalescers has a volume ratio of 1:1 to 1:10 with the vacuum distillate oil.

5. The method according to claim 1, characterized in that, In step S30, the temperature of the regeneration process is 150-250 °C.

6. The method according to claim 1 or 5, characterized in that, In step S40, the temperature of the regeneration process is 120-150 °C.

7. The method according to claim 1, characterized in that, Each polar fiber bundle (22) has a length of 1000-3000 mm and a diameter of 1-200 micrometers.

8. The method according to claim 1, characterized in that, In the deacidification mixing coalescer and the back-extraction mixing coalescer (7), the structured packing is selected from at least one of structured packing 125Y, structured packing 250Y, structured packing 350Y, structured packing 450Y, structured packing 500Y and structured packing 700Y.

9. The method according to claim 1, characterized in that, The method further includes: returning the regenerated back-extractant to the back-extraction mixing coalescer (7) for recycling; The method further includes returning the regenerated deacidifying agent to the deacidification unit for recycling.

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