Deacidification method for vacuum distillate oil

Abstract

The invention relates to the technical field of distillate oil refining, and discloses a vacuum distillate oil deacidification method which comprises the following steps: S10, performing deacidification treatment on vacuum distillate oil and a deacidification agent in a deacidification unit; s20, carrying out extraction separation on the obtained deacidification agent to be generated and a back extraction agent in a back extraction mixing coalescer; s30, the separated supernatant liquid is conveyed to a back extractant regeneration device for regeneration treatment; s40, the separated lower-layer liquid enters a deacidification agent regeneration device to be subjected to regeneration treatment; the deacidification unit comprises one or more deacidification mixing coalescers, each of the deacidification mixing coalescers and the back extraction mixing coalescers comprises a shell, each shell is provided with a premixing area, a coalescence separation area and a settling separation area from top to bottom, structured packing is arranged in the premixing areas, and polar fiber bundles are arranged in the coalescence separation areas; the deacidification agent contains organic amine, a cosolvent and water. The method can be used for deacidification treatment of vacuum distillate oil with high viscosity and high acid value, and is wide in application range.

Description

Technical Field

[0001] The present invention relates to the technical field of fraction oil refining, and particularly relates to a method for removing acid from vacuum gas oil. Background Art

[0002] With the increase in energy demand and the depletion of conventional low-acid crude oils, the demand for high-acid crude oils is increasing year by year due to their abundance and relatively low price. However, the processing of high-acid crude oils and their vacuum gas oils can cause serious corrosion problems to equipment, affecting the long-term safe operation of refinery units. At the same time, it also makes the acid value of the refined products too high, affecting their use. In addition, naphthenic acid, the main acidic substance in fraction oil, is an important fine chemical raw material with high application value and wide uses. For example, naphthenic acid and its derivatives (metal esters and salts, naphthenates) can be used as lubricants, emulsifiers, paint driers, oxidation catalysts, wood preservatives, etc. in industry.

[0003] Traditional processing of high-acid vacuum gas oil often uses caustic refining or mixing with low-acid fraction oil to reduce the acid value of the fraction oil. The former consumes a large amount of acid and alkali, has serious oil-water emulsification, produces a large amount of waste liquid and alkali slag, pollutes the environment, and also causes equipment corrosion; the latter, although reducing the acid value of the oil product, still has naphthenic acid in the fraction oil, which will still corrode the equipment at higher temperatures and cannot fundamentally solve the problem. Therefore, it is of great significance to develop a clean, environmentally friendly, economical, efficient, simple and universal process for removing acid from high-acid vacuum gas oil.

[0004] In recent years, there have been various processes for removing naphthenic acid from fraction oil at home and abroad. For example, US5891325 discloses a method for thermal decomposition and acid removal at high temperature, which can thermally decompose naphthenic acid into alkanes and carbon dioxide, thereby reducing the acid value of the oil product. However, this method requires a relatively high temperature, has high energy consumption, and is prone to decomposition of other components in the fraction oil, resulting in a reduction in the oil product yield; in addition, the structure of naphthenic acid is damaged and it cannot be recycled. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems existing in the prior art, and provide a method for removing acid from vacuum gas oil that is clean, environmentally friendly, economical, efficient, and simple. This method can not only achieve acid removal for high-acid value and high-viscosity oil products, but also avoid the loss of the acid remover and environmental pollution caused by the mutual entrainment or emulsification of the acid remover and the vacuum gas oil, and can recycle naphthenic acid with high application value.

[0006] To achieve the above purpose, the present invention provides a method for removing acid from vacuum gas oil, which includes the following steps: S10. Perform acid removal treatment on the vacuum gas oil and the acid remover in an acid removal unit to obtain the spent acid remover and the treated vacuum gas oil respectively; S20. Extract and separate the spent deacidifying agent and the stripping agent in a stripping mixing coalescer; S30. Transport the upper-layer liquid separated from the stripping mixing coalescer to a stripping agent regeneration device for regeneration treatment to obtain a regenerated stripping agent; S40. Transport the lower-layer liquid separated from the stripping mixing coalescer to a deacidifying agent regeneration device for regeneration treatment to obtain naphthenic acid and a regenerated deacidifying agent respectively; Wherein, the deacidifying unit includes one or more deacidifying mixing coalescers, and each of the deacidifying mixing coalescer and the stripping mixing coalescer includes a housing, and a premixing zone, a coalescing separation zone and a settling separation zone are sequentially arranged in the housing from top to bottom. Structured packing is arranged in the premixing zone, and polar fiber bundles are arranged in the coalescing separation zone. A liquid inlet is arranged at the top of the premixing zone, and an upper-layer liquid outlet and a lower-layer liquid outlet are respectively arranged at the side and bottom of the settling separation zone; The deacidifying agent contains organic amine, cosolvent and water. The organic amine is selected from at least one of diethylamine, triethylamine, ethylenediamine, n-propylamine, n-butylamine and N,N-dimethylethanolamine, and the cosolvent is selected from at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol.

[0007] Preferably, the deacidifying unit includes three deacidifying mixing coalescers, which are a primary deacidifying mixing coalescer, a secondary deacidifying mixing coalescer and a tertiary deacidifying mixing coalescer respectively along the material flow direction of the vacuum gas oil. The lower-layer liquid outlet of the primary deacidifying mixing coalescer is connected to the liquid inlet of the secondary deacidifying mixing coalescer, and the lower-layer liquid outlet of the secondary deacidifying mixing coalescer is connected to the liquid inlet of the tertiary deacidifying mixing coalescer.

[0008] Preferably, the deacidifying agent transported to the primary deacidifying mixing coalescer contains diethylamine, isopropanol and water. The deacidifying agent transported to the secondary deacidifying mixing coalescer contains diethylamine, isopropanol and water. The deacidifying agent transported to the tertiary deacidifying mixing coalescer contains ethylenediamine, n-propanol and water.

[0009] Preferably, the volume ratio of the total deacidifying agent added to the three deacidifying mixing coalescers to the vacuum gas oil is 1:1 - 1:1,0.

[0010] 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%.

[0011] Preferably, in step S20, the stripping agent is selected from at least one of solvent oil D30, solvent oil D40, solvent oil D60, solvent oil D80, and solvent oil D100.

[0012] Preferably, in step S30, the temperature of the regeneration treatment is 150 - 250 °C.

[0013] Preferably, in step S40, the temperature of the regeneration treatment is 120 - 150 °C.

[0014] Preferably, the material of the polar fiber bundle is selected from at least one of hydrophilically modified polyacrylonitrile fiber, hydrophilically modified stainless steel fiber, and hydrophilically modified polylactic acid fiber.

[0015] Preferably, the water contact angle of the polar fiber bundle is 10° - 65°.

[0016] Preferably, the length of each polar fiber bundle is 1000 - 3000 mm, and the diameter is 1 - 200 microns.

[0017] Preferably, in the deacidification mixing coalescer and the stripping 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.

[0018] Preferably, in the deacidification mixing coalescer and the stripping mixing coalescer, the lower liquid outlet is connected with an elbow pipe, and the elbow pipe is located below the upper liquid outlet.

[0019] Preferably, the method further includes: returning the regenerated stripping agent to the stripping mixing coalescer for recycling.

[0020] Preferably, the method further includes: returning the regenerated deacidifying agent to the deacidification unit for recycling.

[0021] In the technical solution provided by the present invention, through the design of the components of the deacidifying agent, it can efficiently remove acid; by using a deacidifying mixed coalescer filled with polar fiber bundles to remove acid from the vacuum distillate oil, while further improving the deacidification effect, it avoids the loss of the deacidifying agent and environmental pollution caused by the entrainment or emulsification of the deacidifying agent and the vacuum distillate oil, making the treated vacuum distillate oil of high quality, and the recovery rate and purity of the regenerated deacidifying agent are high, and downstream sedimentation or water washing equipment is not required, saving investment and floor area; compared with conventional alkali washing deacidification, sedimentation tank separation, conventional coalescer deacidification and other technologies, in the method of the present invention, the flow rate of the liquid in the fiber bundle is fast (0.5 - 2 m / s), having advantages such as large processing capacity and high efficiency, and the treated distillate oil and the spent deacidifying agent can quickly coalesce and separate in the mixed coalescer and be continuously discharged; by using a back-extraction mixed coalescer to extract and separate the spent deacidifying agent (containing naphthenic acid amide salt and deacidifying agent), the separation effect is good, improving the purity of the recovered naphthenic acid and the quality of the regenerated back-extraction agent and deacidifying agent, enabling the back-extraction agent and deacidifying agent to be recovered and recycled with low energy consumption and high efficiency.

[0022] Therefore, the method of the present invention has a good deacidification effect, can realize the deacidification treatment of vacuum distillate oil with high viscosity and high acid value, and thus can be used for the deacidification treatment of vacuum distillate oil with different viscosities and acid values, with a wide range of applications, and the entire process is simple to operate, mild in conditions, and environmentally friendly; the back-extraction agent and deacidifying agent can be recycled, and naphthenic acid can be recycled, with broad application prospects. Description of the Drawings

[0023] Figure 1 is a schematic structural diagram of an embodiment of a vacuum distillate oil deacidification system for implementing the vacuum distillate oil deacidification method provided by the present invention; Figure 2 is Figure 1 a schematic structural diagram of the deacidifying mixed coalescer in

[0024] Description of the Reference Numerals in the Drawings: 1. Deacidifying Agent Supply Device; 2. Feed Pump; 3. Primary Deacidifying Mixed Coalescer; 4. Secondary Deacidifying Mixed Coalescer; 5. Tertiary Deacidifying Mixed Coalescer; 6. Spent Deacidifying Agent Storage Device; 7. Back-Extraction Mixed Coalescer; 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; 20. Shell; 201. Premixing Zone; 202. Coalescing and Separating Zone; 203. Sedimentation and Separating Zone; 21. Structured Packing; 22. Polar Fiber Bundle; 23. Mounting Plate; 24. Elbow; 25. Baffle. Detailed Embodiments

[0025] The following provides a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for explaining and illustrating the present invention and are not used to limit the present invention.

[0026] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0027] The present invention provides a method for removing acid from vacuum gas oil, and the method includes the following steps: S10: Subject the vacuum gas oil to acid removal treatment with an acid removal agent in an acid removal unit to obtain a spent acid removal agent and the treated vacuum gas oil respectively; S20: Perform extraction separation on the spent acid removal agent and an anti-extraction agent in an anti-extraction mixing coalescer 7; S30: Transport the upper layer liquid separated in the anti-extraction mixing coalescer 7 to an anti-extraction agent regeneration device 9 for regeneration treatment to obtain a regenerated anti-extraction agent; S40: Transport the lower layer liquid separated in the anti-extraction mixing coalescer 7 to the acid removal agent regeneration device 12 for regeneration treatment to obtain naphthenic acid and a regenerated acid removal agent respectively; Wherein, the acid removal unit includes one or more acid removal mixing coalescers, and each of the acid removal mixing coalescer and the anti-extraction mixing coalescer 7 includes a housing 20. The housing 20 is sequentially provided with a premixing zone 201, a coalescence separation zone 202, and a sedimentation separation zone 203 from top to bottom. A structured packing 21 is arranged in the premixing zone 201, a polar fiber bundle 22 is arranged in the coalescence separation zone 202. An inlet for liquid is arranged at the top of the premixing zone 201, and an upper layer liquid outlet and a lower layer liquid outlet are respectively arranged at the side and bottom of the sedimentation separation zone 203; The acid removal 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, and the co-solvent is selected from at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol.

[0028] The method of the present invention is used to remove naphthenic acid from vacuum gas oil. Among them, the vacuum gas oil to be subjected to acid removal treatment can be various gas oils obtained by vacuum distillation, such as the second reduced line gas oil, the third reduced line gas oil, etc.

[0029] When the viscosity or acid value of the vacuum gas oil to be treated is higher, it is more difficult to remove the acid therein. In the method described in the present invention, the deacidifying agent is compounded by using the above-mentioned organic amine, cosolvent and water, so that the obtained deacidifying agent can efficiently remove naphthenic acid in the vacuum gas oil under mild conditions; at the same time, the current conventional oil deacidification method is: stirring and mixing the deacidifying agent with the oil to be treated, and then standing and separating by using a settling tank or a separating funnel. In this way, the mixing effect of the deacidifying agent and the oil is poor, and they are easily entrained with each other, resulting in poor deacidification effect. However, in the method described in the present invention, a deacidification mixing coalescer filled with structured packing 21 and polar fiber bundles 22 is used for pre-mixing of the structured packing 21. The polar fiber bundles 22 increase the contact area between the deacidifying agent and the vacuum gas oil, strengthen coalescence separation and efficient deacidification, avoiding the loss of the deacidifying agent and environmental pollution caused by the mutual entrainment or emulsification of the deacidifying agent and the vacuum gas oil, and further improving the deacidification effect; in addition, by using a back-extraction mixing coalescer 7 to extract and separate the spent deacidifying agent, a small amount of dissolved vacuum gas oil in the spent deacidifying agent is removed, improving the purity of the recovered naphthenic acid and the purity and recovery rate of the regenerated back-extraction agent and deacidifying agent. Therefore, the method described in the present invention can effectively deacidify high-viscosity and high-acid-value vacuum gas oil, and the back-extraction agent and deacidifying agent can be recovered and recycled with low energy consumption and high efficiency, and the naphthenic acid can be recycled, with broad application prospects.

[0030] In the present invention, the vacuum gas oil deacidification method is carried out in a vacuum gas oil deacidification system. Please refer to Figure 1 and Figure 2 , this system includes a deacidifying agent supply device 1, a deacidification unit, a back-extraction mixing coalescer 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 liquid inlet of the deacidification unit, the upper liquid outlet of the deacidification unit is communicated with the inlet of the back-extraction mixing coalescer 7, the upper liquid outlet of the back-extraction mixing coalescer 7 is connected to the back-extraction agent regeneration device 9, and the lower liquid outlet of the back-extraction mixing coalescer 7 is connected to the deacidifying agent regeneration device 12.

[0031] In a specific embodiment, the structures of the back-extraction agent regeneration device 9 and the deacidifying agent regeneration device 12 are the same, and both are conventional regeneration towers in the art.

[0032] In the method of the present invention, the deacidifier is prepared by compounding the specifically selected organic amine with low molecular weight alcohol and water. The deacidifier composed of the above components has the following advantages: 1. The synergistic effect of the organic amine, low molecular weight alcohol and water enhances the deacidification effect of the vacuum distillate oil, and the organic amine and low molecular weight alcohol are easy to recycle subsequently; the organic amine reacts with naphthenic acid to form an amine salt. This reaction process is mild, without harsh reaction conditions, and the reaction products are easy to separate. At the same time, the organic amine does not introduce other impurities or have an adverse effect on other properties of the oil product, ensuring the quality of the oil product; 2. Compared with the traditional alkali washing deacidification process, the synergistic deacidification of the organic amine, low molecular weight alcohol and water does not use strongly corrosive alkali solution, reducing the corrosion of equipment and the equipment maintenance cost; it is not easy to cause emulsification phenomenon, avoiding oil product loss and subsequent treatment difficulties caused by emulsification; 3. The operation temperature for removing naphthenic acid by the synergistic effect of the organic amine, low molecular weight alcohol and water is usually carried out in the range of normal temperature to low temperature. Compared with the traditional high-temperature and high-pressure deacidification process, the energy consumption is reduced; 4. The synthesis raw materials of the organic amine and low molecular weight alcohol are widely available and the synthesis process is mature.

[0033] In a preferred embodiment, based on the total volume of the deacidifier, 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 the water is 5%-40%. By using the deacidifier with the above ratio, the deacidification effect is better.

[0034] Further preferably, based on the total volume of the deacidifier, 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%.

[0035] The present invention does not limit the number of deacidification mixing coalescers in the deacidification unit, which can be 1, 2, 3, 4, etc. In a preferred embodiment, the deacidification unit includes three deacidification mixing coalescers, namely the primary deacidification mixing coalescer 3, the secondary deacidification mixing coalescer 4 and the tertiary deacidification mixing coalescer 5 along the material flow direction of the vacuum distillate oil. The lower liquid outlet of the primary deacidification mixing coalescer 3 is connected to the liquid inlet of the secondary deacidification mixing coalescer 4, and the lower liquid outlet of the secondary deacidification mixing coalescer 4 is connected to the liquid inlet of the tertiary deacidification mixing coalescer 5.

[0036] In specific implementation, the deacidifier reacts with the vacuum gas oil in the first-stage deacidification mixing coalescer 3 for reactive extraction deacidification. The obtained lower-layer liquid (deacidified vacuum gas oil) successively passes through the second-stage deacidification mixing coalescer 4 and the third-stage deacidification mixing coalescer 5 to react and extract deacidification step by step with the added fresh deacidifier. The refined vacuum gas oil is obtained at the lower layer of the third-stage deacidification mixing coalescer 5. By subjecting the vacuum gas oil to three-stage deacidification treatment, the deacidification effect of the vacuum gas oil can be significantly improved, and the consumption of the deacidifier is low. In this embodiment, the upper-layer liquids (spent deacidifiers) obtained from the first-stage deacidification mixing coalescer 3, the second-stage deacidification mixing coalescer 4, and the third-stage deacidification mixing coalescer 5 are all transported to the back-extraction mixing coalescer 7 for treatment.

[0037] In some embodiments, the deacidifiers in the first-stage deacidification mixing coalescer 3, the second-stage deacidification mixing coalescer 4, and the third-stage deacidification mixing coalescer 5 have the same composition. In this way, the operation is simple and the cost is low.

[0038] In this embodiment, the deacidifier supply device 1 is respectively connected to the first-stage deacidification mixing coalescer 3, the second-stage deacidification mixing coalescer 4, and the third-stage deacidification mixing coalescer 5 through the feed pump 2, and is used to provide deacidifiers with the same composition to the first-stage deacidification mixing coalescer 3, the second-stage deacidification mixing coalescer 4, and the third-stage deacidification mixing coalescer 5. In this embodiment, the spent deacidifiers obtained from the first-stage deacidification mixing coalescer 3, the second-stage deacidification mixing coalescer 4, and the third-stage deacidification mixing coalescer 5 are first centrally transported to the spent deacidifier storage device 6, and then transported to the back-extraction mixing coalescer 7 for treatment. In specific implementation, the upper-layer liquid outlets of the first-stage deacidification mixing coalescer 3, the second-stage deacidification mixing coalescer 4, and the third-stage deacidification mixing coalescer 5 are all connected to the liquid inlet of the spent deacidifier storage device 6, and the outlet of the spent deacidifier storage device 6 is connected to the inlet of the back-extraction mixing coalescer 7.

[0039] In other embodiments, the deacidifiers in the first-stage deacidification mixing coalescer 3, the second-stage deacidification mixing coalescer 4, and the third-stage deacidification mixing coalescer 5 have different compositions. Preferably, the deacidifier transported to the first-stage deacidification mixing coalescer 3 contains diethylamine, isopropanol, and water, the deacidifier transported to the second-stage deacidification mixing coalescer 4 contains diethylamine, isopropanol, and water, and the deacidifier transported to the third-stage deacidification mixing coalescer 5 contains ethylenediamine, n-propanol, and water. By successively treating the vacuum gas oil to be deacidified with the deacidifiers of the above components, when the acid value of the gas oil is relatively high, the deacidifiers of the first two-stage deacidification mixing coalescers use diethylamine and isopropanol with moderate polarity and relatively low boiling points to remove most of the naphthenic acids in the gas oil, and the deacidifier of the third-stage deacidification mixing coalescer uses ethylenediamine and n-propanol with relatively strong polarity and relatively high boiling points to remove the remaining naphthenic acids in the gas oil at a deeper level. In this way, not only can effective deacidification be achieved while facilitating the centralized recovery and recycling of the deacidifier, but also energy consumption can be saved.

[0040] In this embodiment, the number of the deacidifying agent supply devices 1 is two. One of the deacidifying agent supply devices 1 is respectively connected to the primary deacidification mixing coalescer 3 and the secondary deacidification mixing coalescer 4, so as to transport deacidifying agents with the same composition into the primary deacidification mixing coalescer 3 and the secondary deacidification mixing coalescer 4. The other deacidifying agent supply device 1 is connected to the tertiary deacidification mixing coalescer 5 to provide a deacidifying agent with a different composition to the tertiary deacidification mixing coalescer 5.

[0041] Preferably, in this embodiment, the number of the spent deacidifying agent storage devices 6, the back-extraction mixing coalescers 7 and the deacidifying agent regeneration devices 12 is also two. Specifically, one of the two back-extraction mixing coalescers 7 is connected to the primary deacidification mixing coalescer 3 and the secondary deacidification mixing coalescer 4, and the other is connected to the tertiary deacidification mixing coalescer 5; one of the two deacidifying agent regeneration devices 12 is correspondingly connected to the primary deacidification mixing coalescer 3 and the secondary deacidification mixing coalescer 4, and the other is correspondingly connected to the tertiary deacidification mixing coalescer 5; one of the two spent deacidifying agent storage devices 6 is connected to the primary deacidification mixing coalescer 3 and the secondary deacidification mixing coalescer 4, and the other is connected to the tertiary deacidification mixing coalescer 5.

[0042] In a specific embodiment, the deacidifying agent supply device 1 and the spent deacidifying agent storage device 6 have the same structure, and both are conventional storage tanks in the art.

[0043] In the present invention, the amounts of the deacidifying agents in the primary deacidification mixing coalescer, the secondary deacidification mixing coalescer and the tertiary deacidification mixing coalescer may be the same or different, and can be specifically adjusted according to the actual situation. In a preferred embodiment, the volume ratio of the total deacidifying agent added to the vacuum distillate oil in the three deacidification mixing coalescers (the primary deacidification mixing coalescer 3, the secondary deacidification mixing coalescer 4 and the tertiary deacidification mixing coalescer 5) is 1:1 - 1:10. Further preferably, the amounts of the deacidifying agents in the primary deacidification mixing coalescer 3, the secondary deacidification mixing coalescer 4 and the tertiary deacidification mixing coalescer 5 are the same.

[0044] 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.

[0045] In some embodiments, in step S30, the temperature of the regeneration treatment is 150 - 250 °C. By maintaining the stripping agent regeneration device 9 within the above temperature range, the upper-layer liquid separated from the back-extraction mixing coalescer 7 is regenerated. A refined vacuum distillate oil (i.e., the vacuum distillate oil after acid removal) is obtained at the bottom of the stripping agent regeneration device 9, and a regenerated stripping agent is obtained at the top of the tower. The quality of this stripping agent is high and it can be returned to the back-extraction mixing coalescer 7 for multiple cycles of use.

[0046] In some embodiments, the method further includes: returning the regenerated stripping agent to the back-extraction mixing coalescer 7 for recycling.

[0047] In some embodiments, before the upper-layer liquid from the back-extraction mixing coalescer 7 enters the stripping agent regeneration device 9, it first enters the first heat exchanger 8 for heating treatment.

[0048] In a specific embodiment, step S30 includes: the upper-layer liquid from the back-extraction mixing coalescer 7 enters the first heat exchanger 8 for heating treatment, then enters the stripping agent regeneration device 9 for regeneration treatment. A refined vacuum distillate oil is obtained at the bottom of the tower, and the steam at the top of the tower is condensed to obtain a regenerated stripping agent. The regenerated stripping agent is returned to the back-extraction mixing coalescer 7 for recycling.

[0049] In some embodiments, in step S40, the temperature of the regeneration treatment is 120 - 150 °C. By maintaining the deacidifying agent regeneration device 12 within the above temperature range, the lower-layer liquid separated from the back-extraction mixing coalescer 7 is regenerated. A 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 purity of the regenerated deacidifying agent is high and it can be returned to the deacidification unit for multiple cycles of use.

[0050] In some embodiments, the method further includes: returning the regenerated deacidifying agent to the deacidification unit for recycling.

[0051] In some embodiments, before the lower-layer liquid from the back-extraction mixing coalescer 7 enters the deacidifying agent regeneration device 12, it first enters the second heat exchanger 11 for heating.

[0052] In a specific embodiment, step S40 includes: the lower-layer liquid from the back-extraction mixing coalescer 7 enters the second heat exchanger 11 for heating, then enters the deacidifying agent regeneration device 12 for regeneration treatment. Naphthenic acid is obtained at the bottom of the tower, and the steam at the top of the tower is condensed to obtain a regenerated deacidifying agent. The regenerated deacidifying agent is returned to the deacidification unit for recycling.

[0053] In the method according to the present invention, the regeneration treatments in step S30 and step S40 can be carried out under normal pressure conditions.

[0054] In the present invention, each of the deacidification mixed coalescers includes a housing, and a premixing zone 201, a coalescence separation zone 202, and a sedimentation separation zone 203 are sequentially arranged in the housing from top to bottom. Specifically in implementation, the vacuum distillate oil to be treated enters the deacidification mixed coalescer, first enters the premixing zone 201, is mixed with the deacidifying agent through the structured packing 21 and evenly distributed, then enters the coalescence separation zone 202, contacts and reacts with the filled polar fiber bundle, and then is stratified in the sedimentation separation zone 203 to obtain the spent deacidifying agent located in the upper layer and the deacidified vacuum distillate oil located in the lower layer.

[0055] Specifically, the working principles and processes of the coalescence separation zone 202 and the sedimentation separation zone 203 in each of the deacidification mixed coalescers are as follows: The surface tensions of two immiscible liquids presented on the surface of the fiber bundle are different. When the vacuum distillate oil and the polar deacidifying agent flow downward along the polar fiber bundle 22, the deacidifying agent adheres to the fiber surface and is pulled into an extremely thin film, so that small-volume droplets are expanded into a large-area liquid film; The vacuum distillate oil and the deacidifying agent adhering to the fiber bundle rub against each other, causing the surface of the deacidifying agent liquid film adhering to the fiber bundle surface to continuously form undulations, increasing the contact area and the renewal rate of the contact interface, making the reaction more sufficient and greatly improving the deacidification efficiency; In addition, after the deacidifying agent and the vacuum distillate oil complete the contact reaction, a phase separation process occurs. At this time, the vacuum distillate oil is separated from the bottom of the fiber bundle, and the deacidifying agent remains adsorbed on the fiber surface due to strong surface tension and continues to flow downward to the sedimentation separation zone 203 to fall off and form large particles and quickly settle; Moreover, the densities between the oil phase and the water phase are also different. Therefore, the deacidified distillate oil and the spent deacidifying agent quickly form two liquid interfaces in the separation tank. This clean separation method can prevent the deacidified vacuum distillate oil and the spent deacidifying agent from forming mutual entrainment or forming very little mutual entrainment.

[0056] In the present invention, the structures of the deacidification mixed coalescer and the extraction mixed coalescer are the same, except for the treatment objects. Therefore, the working principles of the extraction mixed coalescer and the deacidification mixed coalescer are basically the same and will not be elaborated here.

[0057] In the present invention, in the deacidification mixing coalescer and the extraction mixing coalescer, the upper liquid outlet of the sedimentation separation zone 203 is provided at the side of the sedimentation separation zone 203, and the lower liquid outlet of the sedimentation separation zone 203 is provided at the bottom of the sedimentation separation zone 203. Further, the lower liquid outlet is connected with an elbow pipe 24, and the elbow pipe 24 is located below the upper liquid outlet (i.e., the height of the elbow pipe is lower than the upper liquid outlet of the sedimentation separation zone 203). Through the above design, thus, 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 upper height of the elbow pipe, the lower liquid in the sedimentation separation zone 203 is automatically discharged through the lower liquid outlet, thereby realizing the continuous discharge of the upper liquid and the lower liquid in the sedimentation separation zone 203.

[0058] In a specific embodiment, the elbow pipe is a U-shaped elbow pipe.

[0059] In some embodiments, in step S10, the temperature of the deacidification treatment is 20 - 50 °C. Specifically in implementation, the temperature of the deacidification mixing coalescer is maintained at 20 - 50 °C.

[0060] In the method of the present invention, in step S20, the extraction separation can be carried out at room temperature (21 - 28 °C).

[0061] In a preferred embodiment, in the deacidification mixing coalescer and the back-extraction mixing coalescer 7, the material of the polar fiber bundle 22 is selected from at least one of hydrophilic modified polyacrylonitrile fiber, hydrophilic modified stainless steel fiber, hydrophilic modified polylactic acid fiber, etc., and more preferably hydrophilic modified stainless steel fiber. By selecting the polar fiber bundle 22 of the above material, the deacidification effect on the vacuum distillate oil is better. Among them, the above hydrophilic modified fiber bundle can be directly purchased or prepared by oneself. When prepared by oneself, conventional hydrophilic modification methods in the art can be adopted, such as laser polishing, plasma treatment, ultraviolet radiation treatment, surface grafting treatment, chemical etching, etc.

[0062] In a preferred embodiment, in the deacidification mixing coalescer and the back-extraction mixing coalescer 7, the length of each polar fiber bundle 22 is 1000 - 3000 mm, and the diameter is 1 - 200 microns. In this way, the deacidification effect is good and the cost is low.

[0063] In a preferred embodiment, the water contact angle of the polar fiber bundle 22 is 10° - 65°.

[0064] In some embodiments, the polar fiber bundle 22 extends to 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.

[0065] In a preferred embodiment, the polar fiber bundle 22 is suspended below the structured packing 21, and the polar fiber bundle 22 is completely filled in the housing 20 (the filling area is 95-100%). In this way, the vacuum distillate oil can better contact the polar fiber bundle 22, so that the deacidification effect is better.

[0066] During specific implementation, a mounting plate 23 is provided on the lower surface of the premixing zone 201, and the mounting plate 23 has a plurality of holes, and the polar fiber bundle 22 is suspended on the lower surface of the mounting plate.

[0067] In some embodiments, in the deacidification mixing coalescer and the back-extraction mixing coalescer 7, the cross-sectional area of the sedimentation separation zone 203 in the longitudinal direction is larger than the cross-sectional area of the coalescence separation zone 202 in the longitudinal direction.

[0068] In some embodiments, in the deacidification mixing coalescer and the back-extraction mixing coalescer 7, 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. By providing the baffle 25, the deacidification effect is better.

[0069] In the present invention, by filling the structured packing 21 in the premixing zone 201 of the deacidification mixing coalescer and the back-extraction mixing coalescer 7, the mixing of the materials is more sufficient. In some embodiments, the structured packing 21 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, and preferably structured packing 250Y.

[0070] The present invention will be described in detail below through examples, but the protection scope of the present invention is not limited thereto. The experimental methods in the following examples are all conventional methods in the art unless otherwise specified. The experimental materials used in the following examples are all commercially available products unless otherwise specified.

[0071] In the following examples, room temperature refers to 23±2°C.

[0072] In the following examples, the hydrophilic modified stainless steel fiber bundle used has a hydrophilic modification method of laser roughening, and the water contact angle of the hydrophilic modified stainless steel fiber bundle is 30-40°.

[0073] In the following examples, the test methods involved include: The acid value and basic nitrogen content of the oil sample were tested using a titrator; The viscosity of the oil sample was tested using a full-automatic viscometer; The structure of naphthenic acid was analyzed using a Fourier transform infrared spectrometer.

[0074] Example 1 The vacuum distillate oil to be processed was from a refinery, with an initial acid value (based on KOH, the same below) of 4.52 mg / g and a viscosity (at 20 °C) of 688.86 mm 2 / s.

[0075] This example was carried out in the system shown in Figure 1 The system includes a deacidifying agent supply device 1, a deacidification unit, a spent deacidifying agent storage device 6, an anti-extraction mixing coalescer 7, a first heat exchanger 8, an anti-extraction agent regeneration device 9 (anti-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 deacidification mixing coalescers, which are the first-stage deacidification mixing coalescer 3, the second-stage deacidification mixing coalescer 4, and the third-stage deacidification mixing coalescer 5 along the material flow direction of the vacuum distillate oil; The structure of each deacidification mixing coalescer (the first-stage deacidification mixing coalescer 3, the second-stage deacidification mixing coalescer 4, and the third-stage deacidification mixing coalescer 5) refers to Figure 2 shown, which includes a housing 20. The housing 20 is sequentially provided with a premixing zone 201, a coalescence separation zone 202, and a sedimentation separation zone 203 from top to bottom. A structured packing 21 (structured packing 250Y) is arranged in the premixing zone 201. A polar fiber bundle 22 is filled in the coalescence separation zone 202, and the polar fiber bundle extends to the sedimentation separation zone 203; the material of the polar fiber bundle 22 is a hydrophilic modified stainless steel fiber bundle; the length of the polar fiber bundle 22 is 2000 mm, and the diameter is 50 microns. A liquid inlet is arranged at the top of the premixing zone 201; an upper liquid outlet is arranged on the side of the sedimentation separation zone 203, and a lower liquid outlet is arranged at the bottom of the sedimentation separation zone 203, and the upper liquid outlet is 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 with an elbow 24, and the height of the elbow 24 is lower than the upper liquid outlet; The structure of the anti-extraction mixing coalescer 7 is the same as that of the deacidification mixing coalescer; The deacidifying agent supply device 1 is connected to a primary deacidifying mixing coalescer 3, a secondary deacidifying mixing coalescer 4, and a tertiary deacidifying mixing coalescer 5 through a feed pump 2. The lower liquid outlet of the primary deacidifying mixing coalescer 3 is connected to the liquid inlet of the secondary deacidifying mixing coalescer 4. The lower liquid outlet of the secondary deacidifying mixing coalescer 4 is connected to the liquid inlet of the tertiary deacidifying mixing coalescer 5. Moreover, the upper liquid outlets of the primary deacidifying mixing coalescer 3, the secondary deacidifying mixing coalescer 4, and the tertiary deacidifying mixing coalescer 5 are connected to the spent deacidifying agent storage device 6. The spent deacidifying agent storage device 6 is connected to the inlet of a back-extraction mixing coalescer 7; The upper liquid outlet of the back-extraction mixing coalescer 7 is successively connected to a first heat exchanger 8 and a back-extraction agent regeneration device 9. The top outlet of the back-extraction agent regeneration device 9 is connected to a first condenser 10. The lower liquid outlet of the back-extraction agent is successively connected to the second heat exchanger 11 and a deacidifying agent regeneration device 12. The top outlet of the deacidifying agent regeneration device 12 is connected to a second condenser 13.

[0076] 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.

[0077] The method for deacidifying vacuum gas oil includes the following steps: (1) The fresh deacidifying agent from the deacidifying agent supply device 1 and the vacuum gas oil to be treated are respectively pumped into the primary deacidifying mixing coalescer 3 for mixing, reaction, and separation. The volume of the fresh deacidifying agent added to the secondary deacidifying mixing coalescer 4 and the tertiary deacidifying mixing coalescer 5 is the same as that of the primary deacidifying mixing coalescer 3. The ratio of the total volume of the deacidifying agent added to the primary deacidifying mixing coalescer 3, the secondary deacidifying mixing coalescer 4, and the tertiary deacidifying mixing coalescer 5 to the volume of the vacuum gas oil is 3:4. The reaction and separation temperature of each deacidifying mixing coalescer (the primary deacidifying mixing coalescer 3, the secondary deacidifying mixing coalescer 4, and the tertiary deacidifying mixing coalescer 5) is 30 °C; the lower liquid of the primary deacidifying mixing coalescer 3 is successively treated by the secondary deacidifying mixing coalescer 4 and the tertiary deacidifying mixing coalescer 5, and refined vacuum gas oil is obtained at the lower liquid outlet of the tertiary deacidifying mixer. The spent deacidifying agent at the upper liquid outlet of each deacidifying mixing coalescer first enters the spent deacidifying agent storage device 6 centrally; (2) The back-extraction agent and the spent deacidifying agent from the spent deacidifying agent storage device 6 are respectively fed into the back-extraction mixing coalescer 7 for mixing and back-extraction separation at room temperature; (3) The upper liquid of the back-extraction mixing coalescer 7 is heated by the first heat exchanger 8 and then transported to the back-extraction agent regeneration tower for regeneration at 180 °C. The overhead steam is condensed by the first condenser 10 to obtain the regenerated back-extraction agent, and the bottom of the tower is refined vacuum gas oil; (4)After heating the lower-layer liquid of the back-extraction mixing coalescer 7 through the second heat exchanger 11, it is transported to the deacidifying agent regeneration tower for regeneration at 140 °C. The steam at the top of the tower is condensed by the second condenser 13 to obtain the regenerated deacidifying agent, and naphthenic acid is recovered at the bottom of the tower.

[0078] The refined vacuum distillate oil at the outlet of the refined vacuum distillate oil in the detection system, the naphthenic acid at the outlet of the naphthenic acid, and the regenerated deacidifying agent at the outlet of the second condenser 13 are detected. The experimental results are as follows: The acid value of the refined vacuum distillate oil is 0.012 mgKOH / g, and the deacidification rate is 99.73%, meeting the standard of the general lubricating oil base oil PCL 150SN; the organic amine entrained in the refined vacuum distillate oil is less than 5 ppm; The acid value of the recovered naphthenic acid is 179.5 mgKOH / g, and the purity is 99.5%, meeting the quality standard of the first-grade petroleum acid, acid value 55; The regenerated deacidifying agent is recycled, and the deacidification rate can still reach 99.2% of the fresh deacidifying agent.

[0079] Example 2 Implemented according to the method described in Example 1, except that the vacuum distillate oil to be treated is: the third-stage reduced crude oil fraction, with a viscosity of (20 °C) 16214 mm 2 / s and an acid value of 3.62 mgKOH / g.

[0080] The experimental results of this example are as follows: 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%, meeting the standards of the general lubricating oil base oils PCL 400SN and PCL 150BS; the organic amine entrained in the refined vacuum distillate oil is less than 8 ppm; The acid value of the recovered naphthenic acid is 157.3 mgKOH / g, and the naphthenic acid purity is 99.1%; The regenerated deacidifying agent is recycled, and the deacidification rate can still reach 99.4% of the fresh deacidifying agent.

[0081] Example 3 Implemented according to the method described in Example 1, except that the vacuum distillate oil to be treated is: the second-stage reduced crude oil fraction, with a viscosity of (20 °C) 637.64 mm 2 / s and an acid value of 8.01 mgKOH / g.

[0082] 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 amine entrained in the refined vacuum distillate oil is less than 3 ppm; The acid value of the recovered naphthenic acid is 200.6 mgKOH / g, and the naphthenic acid purity is 99.2%, meeting the quality standard of the acid value of No. 75 for first-grade petroleum acid; The regenerated deacidifying agent is recycled, and the deacidification rate can still reach 99.1% of that of the fresh deacidifying agent.

[0083] Example 4 According to the method described in Example 1, the difference is that the vacuum gas oil to be treated is: the third side stream of vacuum gas oil, with a viscosity of 15418 mm 2 / s at 20 °C and an acid value of 7.52 mgKOH / g.

[0084] The experimental results are as follows: the acid value of the deacidified vacuum gas oil is 0.096 mgKOH / g, and the deacidification rate is 98.72%; the organic amine entrained in the refined vacuum gas oil is less than 10 ppm; The acid value of the recovered naphthenic acid is 180.8 mgKOH / g, and the naphthenic acid purity is 97.9%, meeting the quality standard of the acid value of No. 55 for first-grade petroleum acid; The regenerated deacidifying agent is recycled, and the deacidification rate can still reach 99.1% of that of the fresh deacidifying agent.

[0085] Example 5 According to the method described in Example 4, the difference is that the number of the deacidifying agent supply devices 1 is 2. One supplies the deacidifying agent to the first-stage deacidification mixing coalescer 3 and the second-stage deacidification mixing coalescer 4, and the other supplies the deacidifying agent to the third-stage deacidification mixing coalescer 5. The deacidifying agent supplied to the first-stage deacidification mixing coalescer 3 contains (by volume fraction): 10% diethylamine, 70% isopropanol, and 20% water. The deacidifying agent supplied to the second-stage deacidification mixing coalescer 4 contains (by volume fraction): 10% diethylamine, 70% isopropanol, and 20% water. The deacidifying agent supplied to the third-stage deacidification mixing coalescer 5 contains (by volume fraction): 10% ethylenediamine, 70% n-propanol, and 20% water; the spent deacidifying agent storage device 6, the back-extraction mixing coalescer 7, the back-extraction agent regeneration device 9, and the deacidifying agent regeneration device 12 are also correspondingly provided with 2.

[0086] The vacuum gas oil to be treated (with a viscosity of 15418 mm 2 / s at 20 °C and an acid value of 7.52 mgKOH / g) is treated as above, and the experimental results are as follows: The acid value of the deacidified vacuum gas 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 amine entrained in the refined vacuum gas oil is less than 5 ppm; The acid value of the recovered naphthenic acid is 185.7 mgKOH / g, and the naphthenic acid purity is 98.56%, meeting the quality standard of the acid value of Grade 1 petroleum acid No. 65.

[0087] The regenerated deacidifier is recycled, and the deacidification rate can still reach 99.4% of that of the fresh deacidifier.

[0088] Example 6 It is carried out according to the method described in Example 4. The difference is that the deacidifier used contains the following components by volume fraction: 10% n-propylamine, 70% n-propanol, and 20% water.

[0089] 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 amine entrained in the refined vacuum distillate oil is less than 30 ppm; The acid value of the recovered naphthenic acid is 170.6 mgKOH / g, and the naphthenic acid purity is 96.3%; The regenerated deacidifier is recycled, and the deacidification rate can still reach 98.7% of that of the fresh deacidifier.

[0090] Comparative Example 1 It is carried out according to the method described in Example 4. The difference is that the three deacidification mixed coalescers (primary deacidification mixed coalescer 3, secondary deacidification mixed coalescer 4, and tertiary deacidification mixed coalescer 5) are respectively replaced with a stirrer and a separating funnel, and the separating funnel is allowed to stand for stratification separation.

[0091] The vacuum distillate oil to be treated (viscosity (at 20 °C) 15418 mm 2 / s, acid value 7.52 mgKOH / g) is treated as above. The experimental results are as follows: The acid value of the deacidified vacuum distillate oil is 0.41 mgKOH / g, the deacidification rate is 94.5%, and the organic amine entrained in the refined vacuum distillate oil is greater than 1000 ppm; The acid value of the recovered naphthenic acid is 146.8 mgKOH / g, and the naphthenic acid purity is 80.4%; The deacidification effect of the recycled regenerated deacidifier can reach 90.3% of that of the fresh deacidifier.

[0092] Comparative Example 2 It is carried out according to the method described in Example 4. The difference is that the deacidifier used contains the following components by volume fraction: 10% ammonia water and 90% ethylene glycol.

[0093] The vacuum distillate oil to be treated (viscosity (at 20 °C) 15418 mm 2 / s, acid value 7.52 mgKOH / g) is treated as above. The experimental results are as follows: The acid value of the deacidified vacuum distillate oil is 1.24 mgKOH / g, the deacidification rate is 83.51%, and the organic amine entrained in the refined vacuum distillate oil is less than 50 ppm; The acid value of the recovered naphthenic acid is 143.6 mgKOH / g, and the naphthenic acid purity is 79.3%; The regenerated deacidifying agent is recycled, and the deacidification effect can reach 89.2% of that of the fresh deacidifying agent.

[0094] Comparative Example 3 The method described in Example 4 was carried out, except that the deacidifying agent used contained the following components by volume fraction: 10% cyclohexylamine and 90% glycerol.

[0095] The vacuum distillate oil to be treated (viscosity (at 20 °C) 15418 mm 2 / s, acid value 7.52 mgKOH / g) was treated as described above, and the experimental results were as follows: The acid value of the deacidified vacuum distillate oil is 1.39 mgKOH / g, the deacidification rate is 81.52%, and the organic amine entrained in the refined vacuum distillate oil is less than 20 ppm; The acid value of the recovered naphthenic acid is 139.3 mgKOH / g, and the naphthenic acid purity is 78.1%; The regenerated deacidifying agent is recycled, and the deacidification effect can reach 92.9% of that of the fresh deacidifying agent.

[0096] 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 technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for removing acid from vacuum gas oil, characterized in that, The method comprises the following steps: S10. Subjecting the vacuum distillate oil to deacidification treatment with a deacidifying agent in a deacidification unit to obtain a spent deacidifying agent and the treated vacuum distillate oil respectively; S20. Conducting extraction separation of the spent deacidifying agent and an anti-extraction agent in an anti-extraction mixing coalescer (7); S30. Transporting the upper-layer liquid separated in the anti-extraction mixing coalescer (7) to an anti-extraction agent regeneration device (9) for regeneration treatment to obtain a regenerated anti-extraction agent; S40. Transporting the lower-layer liquid separated in the anti-extraction mixing coalescer (7) to a deacidifying agent regeneration device (12) for regeneration treatment to obtain naphthenic acid and a regenerated deacidifying agent respectively; Wherein, the deacidification unit comprises one or more deacidification mixing coalescers, and each of the deacidification mixing coalescer and the anti-extraction mixing coalescer (7) comprises a housing (20). The housing (20) is sequentially provided with a premixing zone (201), a coalescence separation zone (202) and a sedimentation separation zone (203) from top to bottom. A structured packing (21) is arranged in the premixing zone (201), a polar fiber bundle (22) is arranged in the coalescence separation zone (202), a liquid inlet is arranged at the top of the premixing zone (201), and an upper-layer liquid outlet and a lower-layer liquid outlet are respectively arranged at the side part and the bottom part of the sedimentation separation zone (203); 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, and 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%-25%, the volume fraction of the co-solvent is 50%-80%, and the volume fraction of the water is 5%-40%; The anti-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 material of the polar fiber bundle (22) is selected from at least one of hydrophilically modified polyacrylonitrile fiber, hydrophilically modified stainless steel fiber and hydrophilically modified polylactic acid fiber; 2. The method according to claim 1, wherein The deacidification unit comprises three deacidification mixing coalescers, which are a primary deacidification mixing coalescer (3), a secondary deacidification mixing coalescer (4) and a tertiary deacidification mixing coalescer (5) respectively along the material flow direction of the vacuum distillate oil. The lower-layer liquid outlet of the primary deacidification mixing coalescer (3) is connected to the liquid inlet of the secondary deacidification mixing coalescer (4), and the lower-layer liquid outlet of the secondary deacidification mixing coalescer (4) is connected to the liquid inlet of the tertiary deacidification mixing coalescer (5); 3. The method according to claim 2, wherein The deacidifying agent transported to the primary deacidification mixing coalescer (3) contains diethylamine, isopropanol and water; The deacidifying agent transported to the secondary deacidification mixing coalescer (4) contains diethylamine, isopropanol and water; The deacidifying agent transported to the tertiary deacidification mixing coalescer (5) contains ethylenediamine, n-propanol and water; 4. The method according to claim 2 or 3, characterized in that: The volume ratio of the total deacidifying agent added to the three deacidification mixing coalescers to the vacuum distillate oil is 1:1 - 1:

10.

5. The method according to claim 1, wherein In step S30, the temperature of the regeneration treatment is 150 - 250 °C.

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

7. The method according to claim 1, characterized in that The water contact angle of the polar fiber bundle (22) is 10° - 65°.

8. The method according to claim 1 or 7, characterized in that The length of each polar fiber bundle (22) is 1000 - 3000 mm, and the diameter is 1 - 200 microns.

9. The method according to claim 1, wherein 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; In the deacidification mixing coalescer and the back-extraction mixing coalescer (7), the lower liquid outlet is connected with an elbow pipe (24), and the elbow pipe (24) is located below the upper liquid outlet.

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

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