CN108690658B - Method for recovering aromatic hydrocarbons in low aromatic hydrocarbon content oil - Google Patents

Method for recovering aromatic hydrocarbons in low aromatic hydrocarbon content oil Download PDF

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CN108690658B
CN108690658B CN201710224839.7A CN201710224839A CN108690658B CN 108690658 B CN108690658 B CN 108690658B CN 201710224839 A CN201710224839 A CN 201710224839A CN 108690658 B CN108690658 B CN 108690658B
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extraction
tower
aromatic hydrocarbon
oil
discharged
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CN108690658A (en
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王艳飞
唐晓东
曹耀武
周金波
任海鸥
李晶晶
程中克
苟文甲
董炳利
马艳捷
施红
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Petrochina Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G53/00—Treatment of hydrocarbon oils, in the absence of hydrogen, by two or more refining processes
    • C10G53/02—Treatment of hydrocarbon oils, in the absence of hydrogen, by two or more refining processes plural serial stages only
    • C10G53/04—Treatment of hydrocarbon oils, in the absence of hydrogen, by two or more refining processes plural serial stages only including at least one extraction step
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
    • C10G2300/40—Characteristics of the process deviating from typical ways of processing
    • C10G2300/4025—Yield
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
    • C10G2300/40—Characteristics of the process deviating from typical ways of processing
    • C10G2300/4081—Recycling aspects
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G2400/00—Products obtained by processes covered by groups C10G9/00 - C10G69/14
    • C10G2400/30—Aromatics

Abstract

The invention relates to a method for recovering aromatic hydrocarbon in low aromatic hydrocarbon content oil. The method has the advantages of mild operation conditions, low comprehensive energy consumption and good aromatic hydrocarbon removing effect, and is suitable for recovering aromatic hydrocarbon from a mixture with low aromatic hydrocarbon content.

Description

Method for recovering aromatic hydrocarbons in low aromatic hydrocarbon content oil
Technical Field
The invention relates to a method for recycling aromatic hydrocarbon in low aromatic hydrocarbon content oil for oil refining or chemical enterprises.
Background
As a main means for industrially separating aromatic hydrocarbons in reformate and pyrolysis gasoline, aromatic hydrocarbon extraction is divided into liquid-liquid extraction and extractive distillation according to the process principle. The liquid-liquid extraction is to separate aromatic hydrocarbon from non-aromatic hydrocarbon by utilizing the difference of the solubility of each component of hydrocarbon in a solvent.
The traditional liquid-liquid extraction process is that wide distillate oil is cut and then is sent to the middle part of an extraction tower through a feed pump, a poor solvent such as dimethyl sulfoxide, sulfolane, N-methylpyrrolidone, N-formylmorpholine, tetraethyleneglycol and the like is added from the upper part of the extraction tower, two phases are in countercurrent contact, aromatic hydrocarbon and a small amount of non-aromatic hydrocarbon in an extraction raw material enter the solvent to form a rich solvent, and the rich solvent is extracted from the bottom of the extraction tower and enters the upper part of a stripping tower. The raffinate oil containing the solvent and a small amount of aromatic hydrocarbon is extracted from the top of the extraction tower. Non-aromatic hydrocarbons in the rich solvent are heated and distilled by a stripping tower and are evaporated from the top of the tower, and the cooled non-aromatic hydrocarbons are pumped back to the lower part of the extraction tower by a back washing pump to be used as back washing liquid. The aromatic hydrocarbon and the solvent are extracted from the bottom of the stripping tower and are sent to the middle part of a solvent recovery tower, the separation of the aromatic hydrocarbon and the solvent is realized through reduced pressure distillation, the mixed aromatic hydrocarbon is at the top of the tower, the poor solvent which is recycled is at the bottom of the tower, the poor solvent needs to be supplemented in real time, a certain volume ratio is kept, and otherwise, the efficiency of recovering the aromatic hydrocarbon is lowered.
When the wide-fraction reformed gasoline is treated by the process, the raw materials need to be cut to remove light fractions and heavy gasoline, so that the energy consumption and the operation cost are high, and the heavy components are sent out of a device and cannot be recycled. CN99101697.1 discloses an aromatic extraction process, which can realize C without a heavy component removal tower9Recovering aromatic hydrocarbon, wherein the solvent is selected from sulfolane or tetraethylene glycol, and the aromatic hydrocarbon content is 20-90% C5-C11The hydrocarbon mixture is directly subjected to aromatic extraction to separate non-aromatic hydrocarbon and mixed aromatic hydrocarbon, and the mixed aromatic hydrocarbon is further refined and rectified to obtain an aromatic hydrocarbon product. However, the invention does not have data on aromatic products. The process adopts a mature process method in the prior art, and is different from the prior art in that a heavy component removal tower is not arranged.
CN200610114121 discloses an aromatic extraction method, firstly pumping the extraction feed into the middle part of an extraction tower through a pump, pumping the poor solvent into the upper part of the extraction tower through a pump, extracting under the conventional condition, pumping the raffinate oil out of the top of the extraction tower, pumping the rich solvent out of the bottom of the extraction tower under the self-pressure and entering a stripping tower; the light reflux liquid fraction (51-85 ℃) extracted from the top of the stripping tower enters a reflux tank of the stripping tower through a cooling system, one part of the light reflux liquid fraction reflows to the upper part of the stripping tower, and the other part of the light reflux liquid fraction returns to the lower part of the extraction tower; and the heavy reflux liquid fraction (80-125 ℃) collected from the middle side line of the stripping tower returns to the lower part of the extraction tower through a cooling system and a reflux device; the aromatic hydrocarbon and the solvent are pumped out from the bottom of the stripping tower and sent into a solvent recovery tower through a pump, so that the separation of the aromatic hydrocarbon and the solvent is realized. Although the technology increases the replacement capability of non-aromatic hydrocarbon in rich solvent at the bottom of the extraction tower and improves the back washing effect, the energy consumption of the stripping tower and the solvent recovery tower is high, and the energy consumption is higher during the treatment of low aromatic hydrocarbon raw oil with aromatic hydrocarbon content less than 25%. CN1408689A discloses a method for recovering aromatic hydrocarbons by extraction and extractive distillation, comprising the following steps: (1) pre-fractionating a hydrocarbon mixture to obtain a benzene fraction, a toluene fraction and a mixed xylene fraction; (2) feeding the toluene fraction obtained by pre-fractionation into a liquid-liquid extraction tower from the middle lower part, contacting with a selective solvent entering from the top of the extraction tower for liquid-liquid extraction, discharging an extract phase rich in aromatic hydrocarbon from the bottom of the tower, and discharging non-aromatic hydrocarbon from the top of the tower; (3) introducing the benzene fraction obtained by prefractionation into the middle part of an extraction rectifying tower, and introducing the extract phase obtained in the step (2) into the top of the extraction rectifying tower to contact with a selective solvent entering from the top of the extraction rectifying tower for extraction and rectification, wherein the rich solvent rich in aromatic hydrocarbon is discharged from the bottom of the tower, and non-aromatic hydrocarbon components on the top of the tower flow back to the bottom of a liquid extraction tower; (4) and (4) introducing the rich solvent obtained in the step (3) into a solvent recovery tower from the middle part, distilling under reduced pressure to separate the solvent and aromatic hydrocarbon, discharging mixed aromatic hydrocarbon from the top of the recovery tower, and recycling the poor solvent obtained at the bottom of the recovery tower to a liquid extraction tower and an extractive distillation tower. But the technology aims at 60 to 99 percent of aromatic hydrocarbon raw material mixture.
CN102219649A discloses a method for extracting phenolic compounds from coal liquefied oil or coal tar, which comprises the following steps: 1) distilling to treat coal liquefied oil or coal tar, and cutting all or part of phenol oil fraction at the temperature of <260 ℃; 2) mixing an alcohol aqueous solution or an alcohol amine aqueous solution as an extracting agent with the phenol oil fraction in a mass ratio of 1: 1-10: 1, fully stirring at 20-130 ℃, and layering after mixing; 3) separating and collecting the extractant layer containing phenolic compounds; 4) performing multi-stage back extraction on the phenolic compound in the extractant layer to obtain a back extractant-phenolic solution and an extractant, wherein the extractant is recycled; 5) separating the stripping agent-phenol solution by rectification, recovering the stripping agent, recycling, and separating to obtain a phenol compound; 6) and (4) steam stripping to remove neutral oil carried in the phenolic compound, and finally obtaining a crude phenol product. However, the technology adopts multi-stage extraction in the back extraction process, and the energy consumption is higher. Similarly CN1260341, CN1225081, US 3723256.
The existing aromatic extraction process is not suitable for the raw oil with low aromatic content because of two reasons: the existing aromatic extraction process is suitable for treating raw materials with the aromatic content of 30-90 percent, and has low dearomatization efficiency on raw oil with low aromatic content; secondly, the existing aromatic extraction process is adopted to remove aromatic hydrocarbon from the raw oil with low aromatic hydrocarbon content, the extraction temperature is high, the extractant is easy to decompose, the yield is low, the new supplementary dose is large when the extractant is recycled, and the comprehensive energy consumption is high. Therefore, it is necessary to develop a method for recovering aromatic hydrocarbons from low aromatic hydrocarbon content raw oil, so that the extraction conditions are mild and the aromatic removal efficiency is high.
Disclosure of Invention
The invention aims to recover aromatic hydrocarbon from raw oil with low aromatic hydrocarbon content, so that the extraction condition is mild and the dearomatization efficiency is high.
In order to achieve the purpose, the invention adopts the following technical scheme: a method for recovering aromatic hydrocarbon in low aromatic hydrocarbon content oil comprises the following process steps: the mixed aromatic hydrocarbon product is obtained after the raw oil is subjected to prefractionation, extraction, back extraction, distillation, water washing, water fractionation and separation operation. The back extraction process comprises the step of back extraction of pre-fractionated benzene front distillate and extraction oil discharged from the bottom of the extraction tower to obtain a recyclable extraction agent and extraction oil rich in aromatic hydrocarbon, and the extraction oil is distilled to obtain recyclable benzene front distillate.
The specific operation steps are as follows: firstly, inputting a part of raw oil into a prefractionating tower 1 according to a proportion for prefractionation, discharging benzene front distillate at the tower top, discharging benzene distillation liquid at the tower bottom, mixing the benzene distillation liquid with the rest raw oil, inputting the mixture into an extraction tower 3 for extraction with an extracting agent, obtaining extract oil rich in aromatic hydrocarbon and raffinate oil after extracting the aromatic hydrocarbon after extraction, discharging the extract oil rich in aromatic hydrocarbon from the tower bottom of the extraction tower 3, discharging the raffinate oil from the tower top of the extraction tower 3, sending the raffinate oil discharged from the top of the extraction tower 3 into a feeding mixer A8, then sending the raffinate oil into a settling separator A9, and separating a water phase from an oil phase. The water phase is fed into a coalescing filter A10, the water phase discharged from the coalescing filter A10 is fed into a water fractionating tower 13 for distillation, and the regenerated extractant is discharged from the bottom of the water fractionating tower 13 and is fed into an extractant storage tank 21. And (3) delivering the extraction oil from the bottom of the extraction tower 3 to the upper part of a back extraction tower 4, carrying out back extraction with the benzene front distillate to remove aromatic hydrocarbon in the extraction oil, regenerating an extractant, and discharging the regenerated extractant from the bottom of the extraction tower 4. The extraction oil discharged from the top of the stripping tower 4 passes through heat exchangers 5 and 6 and then is input into a distillation tower 7, aromatic hydrocarbon in the extraction oil is separated from benzene front distillate, the benzene front distillate is discharged from the top of the distillation tower 7 and is input into a stripping agent storage tank 19 through the heat exchanger 5, mixed aromatic hydrocarbon separated from the extraction oil is discharged from the bottom of the distillation tower 7 and is sent into a feed mixer B28 through a heat exchanger 17, washing is carried out, residual extracting agent in the mixed aromatic hydrocarbon is washed away, the washed mixed aromatic hydrocarbon is sent into a settling separator B29 for separation of a water phase and an oil phase, the oil phase is input into a coalescing filter B30, residual water and solvent are removed, and a mixed aromatic hydrocarbon product 12 and raffinate oil 11 are obtained.
The raw oil is as follows: raw oil with aromatic hydrocarbon content of 5-25%; the ratio of the raw oil entering the prefractionator 1 to the extraction tower 3 is 1: 3-3: 1, and especially when the ratio of the raw oil entering the prefractionator 1 to the extraction tower 3 is 10:3, the effect is best.
The pre-fractionation process comprises the following steps: the raw oil lasts for 1.5h-1The volume space velocity of the pre-fractionating tower 1 is input into the pre-fractionating tower from the middle part of the pre-fractionating tower 1 for pre-fractionating, the operating temperature of the pre-fractionating tower 1 is 50-80 ℃, the operating pressure is 0.10-0.15MPa, the benzene front distillate is discharged from the top of the pre-fractionating tower, is cooled by a first condenser 2 and is input into a back extractant storage tank 19, the benzene fraction is discharged from the bottom of the pre-fractionating tower 1 and is separated from the benzene fraction, and the benzene fraction enters an extraction tower 3 to be used as an extraction raw material.
The extraction process comprises the following steps: the benzene fraction liquid discharged from the bottom of the prefractionator 1 is mixed with uncut raw oil to be used as extraction feed for 0.35-0.53h-1The volume space velocity of the extraction solvent is sent to the middle part of an extraction tower 3, the extraction solvent is extracted from an extractant storage tank 21 and is input to the upper part of the extraction tower 3, the extraction solvent and the extraction feed are subjected to liquid-liquid extraction, extraction oil rich in aromatic hydrocarbon and raffinate oil after the extraction of the aromatic hydrocarbon are obtained after the extraction, the volume ratio of the amount of the extraction solvent to the amount of the extraction feed is 1-5, particularly, the effect is optimal when the volume ratio of the amount of the extraction solvent to the amount of the extraction feed is 4, and the operation temperature of the extraction towerThe temperature is 40-80 ℃, the operation pressure is 0.10-0.30MPa, the extraction oil is discharged from the bottom of the tower and enters a stripping tower 4, and the raffinate oil is discharged from the top of the tower; the extraction solvent is one of sulfolane, dimethyl sulfoxide, tetraethylene glycol, N-methylpyrrolidone and N, N-dimethylformamide.
The back extraction process comprises the following steps: and (2) delivering the extraction oil discharged from the bottom of the extraction tower 3 to the upper part of the stripping tower 4, extracting a stripping agent, namely benzene front distillate from a stripping agent storage tank 19, inputting the stripping agent to the lower part of the stripping tower 4, carrying out liquid-liquid extraction on the stripping agent and the extraction oil, wherein the volume ratio of the stripping agent to the extraction oil is 1-3, the operating temperature of the stripping tower 4 is 40-80 ℃, the operating pressure is 0.10-0.30MPa, the regenerated extraction solvent is discharged from the bottom of the stripping tower 4, one part of the regenerated extraction solvent is injected into the lower part of the stripping tower 4, the rest part of the regenerated extraction solvent is input into an extraction agent storage tank 21, and the extraction oil rich in aromatic.
The distillation process comprises the following steps: the extract oil rich in aromatic hydrocarbon is discharged from the top of the stripping tower 4, passes through heat exchangers 5 and 6 and is input into a distillation tower 7, the operating temperature of the distillation tower 7 is 50-100 ℃, and the operating pressure is 0.15-0.40 MPa; the benzene-containing distillate extracted from the middle side line of the distillation tower 7 is pumped into the lower part of the extraction tower 3 to be used as a back washing liquid, and the back washing liquid amount/extraction feeding amount is 0.6-0.8; and the benzene front distillate is discharged from the top of the distillation tower 7 and is input into a back extractant storage tank 19 through a first heat exchanger 5, one part of mixed aromatic hydrocarbon discharged from the bottom of the distillation tower 7 is pumped back to the lower part of the distillation tower 7 through a second condenser 25, and the rest part of the mixed aromatic hydrocarbon is sent into a feed mixer B28 through a fourth heat exchanger 17 for water washing to wash out the residual extractant in the mixed aromatic hydrocarbon.
The water fractionation process comprises the following steps: the water phase discharged from the coalescence filter A10 is sent to a water fractionating tower 13 for distillation, the operation temperature of the water fractionating tower 13 is 85-120 ℃, the operation pressure is 0.05-0.15MPa, and the washing water quantity/substance to be washed by water mass ratio is 0.1-0.3. The water fractionating tower separates water and extractant in the feed material to obtain recyclable and recyclable extractant, which is discharged from the bottom of the water fractionating tower 13 and is input into an extractant storage tank 21.
The separation process comprises the following steps: and (3) conveying the mixed aromatic hydrocarbon at the bottom of the distillation tower 7 from the discharge through a heat exchanger 17 into a feed mixer B28, washing with water to remove residual extractant in the mixed aromatic hydrocarbon, conveying the washed mixed aromatic hydrocarbon into a settling separator B29 to separate a water phase from an oil phase, conveying the oil phase into a coalescing filter B30 to remove residual water and solvent in the oil phase, and obtaining a mixed aromatic hydrocarbon product 12 and raffinate oil 11. The operations of the feed mixer, the sedimentation separator and the coalescing filter are all performed at normal temperature and pressure.
The dearomatization rate of the raw oil with low aromatic hydrocarbon content treated by the method is 85-99 percent, and the total yield is 93-99 percent.
Compared with the prior art, the invention has the following beneficial results:
(1) the rich solvent is back extracted by adopting the light components of the raw oil, the extraction temperature is low, the solvent decomposition is avoided, and the extractant can be regenerated and recycled.
(2) The invention has mild operation condition and high dearomatization efficiency, and is suitable for recovering mixed aromatic hydrocarbon from hydrocarbon mixture with low aromatic hydrocarbon content.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. The drawings and detailed description are not intended to limit the scope of the invention as claimed.
FIG. 1 is a schematic diagram of a process flow and a schematic diagram of an apparatus structure of an aromatic extraction method of the present invention
In the figure: 1. a prefractionation column; 2. a first condenser; 3. an extraction tower; 4. a stripping column; 5. a first heat exchanger; 6. a second heat exchanger; 7. a distillation column; 8. a feed mixer A; 9. a settling separator A; 10. a coalescing filter A; 11. a raffinate oil outlet; 12. an aromatic hydrocarbon outlet; 13. a water fractionation column; 14. a pump A; 15. a third heat exchanger; 16. a pump B; 17. a fourth heat exchanger; 18. a pump C; 19. a stripping agent storage tank; 20. a fifth heat exchanger; 21. an extractant storage tank; 22. a pump D; 23. a pump E; 24. raw oil inlet; 25. a second condenser; 26. a heating coil; 27. a third condenser; 28. a feed mixer B; 29. a settling separator B; 30. coalescing filter B
Detailed Description
Example 1
The aromatic hydrocarbon content of the raw oil is 5.83 percent, the ratio of the raw oil entering the prefractionator 1 to the extraction tower 3 is 1:1, and the feeding volume of the prefractionator is emptySpeed is 1.5h-1The temperature at the bottom of the tower is 75 ℃, the temperature at the top of the tower is 60 ℃, and the operating pressure is 0.15 MPa; the feeding volume space velocity of the extraction tower is 0.53h-1The extracting agent is sulfolane, the solvent ratio (solvent feeding amount/extraction raw material amount) is 1.6, the operation temperature is 55 ℃, and the operation pressure is 0.15 MPa; the volume ratio of the stripping agent to the extraction oil is 1.6, the operation temperature of the stripping tower is 55 ℃, and the operation pressure is 0.15 MPa; the bottom temperature of the distillation tower is 85 ℃, the top temperature of the distillation tower is 60 ℃, the operating pressure is 0.17MPa, the side-line extraction temperature is 75 ℃, and the backwashing ratio is 0.6; the washing water quantity/the quality of the material to be washed is 0.1, the operation temperature of the washing unit is 25 ℃, and the operation pressure is 0.10 MPa; the operation temperature of the water fractionating tower is 90 ℃, and the operation pressure is 0.10 MPa. The dearomatization rate is 86.3 percent, and the total yield is 94.7 percent.
Example 2
The aromatic hydrocarbon content of the raw oil is 24.66 percent, the ratio of the raw oil entering the prefractionator 1 to the extraction tower 3 is 2:1, and the feed volume airspeed of the prefractionator is 1.5h-1The temperature at the bottom of the tower is 80 ℃, the temperature at the top of the tower is 65 ℃, and the operating pressure is 0.13 MPa; the volumetric space velocity of the feeding material of the extraction tower is 0.37h-1The extracting agent is sulfolane, the solvent ratio (solvent feeding amount/extraction raw material amount) is 3.0, the operating temperature is 70 ℃, and the operating pressure is 0.25 MPa; the volume ratio of the back extraction agent to the extraction oil is 2.0, the operation temperature of the back extraction tower is 70 ℃, and the operation pressure is 0.25 MPa; the bottom temperature of the distillation tower is 90 ℃, the top temperature of the distillation tower is 65 ℃, the operating pressure is 0.31MPa, the side-draw temperature is 75 ℃, and the backwashing ratio is 0.8; the washing water quantity/the quality of the material to be washed is 0.1, the operation temperature of the washing unit is 30 ℃, and the operation pressure is 0.12 MPa; the operating temperature of the water fractionating tower is 110 ℃, and the operating pressure is 0.12 MPa. The dearomatization rate is 93.2 percent, and the total yield is 97.1 percent.
Example 3
The aromatic hydrocarbon content of the raw oil is 10.16 percent, the ratio of the raw oil entering the prefractionator 1 to the extraction tower 3 is 3:1, and the feed volume airspeed of the prefractionator is 1.5h-1The temperature at the bottom of the tower is 76 ℃, the temperature at the top of the tower is 61 ℃, and the operating pressure is 0.12 MPa; the space velocity of the feeding volume of the extraction tower is 0.45h-1The extracting agent is sulfolane, the solvent ratio (solvent feeding amount/extraction raw material amount) is 2.2, the operating temperature is 65 ℃, and the operating pressure is 0.20 MPa; the volume ratio of the back extraction agent to the extraction oil is 1.8, the operation temperature of the back extraction tower is 65 ℃, and the operation pressure is 0.20 MPa; the temperature of the bottom of the distillation tower is 86 ℃,the temperature at the top of the tower is 61 ℃, the operating pressure is 0.27MPa, the temperature at the side extraction is 75 ℃, and the back washing ratio is 0.7; the washing water quantity/the quality of the material to be washed is 0.1, the operation temperature of the washing unit is 30 ℃, and the operation pressure is 0.12 MPa; the operation temperature of the water fractionating tower is 100 ℃, and the operation pressure is 0.12 MPa. The dearomatization rate is 90.2 percent, and the total yield is 96.4 percent.
Example 4
The aromatic hydrocarbon content of the raw oil is 10.16 percent, the ratio of the raw oil entering the prefractionator 1 to the extraction tower 3 is 3:1, and the feed volume airspeed of the prefractionator is 1.5h-1The temperature at the bottom of the tower is 74 ℃, the temperature at the top of the tower is 58 ℃, and the operating pressure is 0.11 MPa; the space velocity of the feeding volume of the extraction tower is 0.45h-1N-methyl pyrrolidone is used as an extracting agent, the solvent ratio (solvent feeding amount/extraction raw material amount) is 1.8, the operation temperature is 40 ℃, and the operation pressure is 0.10 MPa; the volume ratio of the back extraction agent to the extraction oil is 1.8, the operation temperature of the back extraction tower is 40 ℃, and the operation pressure is 0.10 MPa; the bottom temperature of the distillation tower is 84 ℃, the top temperature of the distillation tower is 58 ℃, the operating pressure is 0.16MPa, the side-line extraction temperature is 75 ℃, and the backwashing ratio is 0.7; the washing water quantity/the quality of the material to be washed is 0.1, the operation temperature of the washing unit is 25 ℃, and the operation pressure is 0.10 MPa; the operation temperature of the water fractionating tower is 90 ℃, and the operation pressure is 0.10 MPa. The dearomatization rate is 90.9 percent, and the total yield is 95.8 percent.
Example 5
The aromatic hydrocarbon content of the raw oil is 10.16 percent, the ratio of the raw oil entering the prefractionator 1 to the extraction tower 3 is 3:1, and the feed volume airspeed of the prefractionator is 1.5h-1The temperature at the bottom of the tower is 77 ℃, the temperature at the top of the tower is 62 ℃, and the operating pressure is 0.11 MPa; the feeding volume space velocity of the extraction tower is 0.41h-1The extractant is dimethyl sulfoxide, the solvent ratio (solvent feeding amount/extraction raw material amount) is 2.3, the operation temperature is 70 ℃, and the operation pressure is 0.11 MPa; the volume ratio of the stripping agent to the extraction oil is 1.8, the operating temperature of the stripping tower is 70 ℃, and the operating pressure is 0.11 MPa; the bottom temperature of the distillation tower is 88 ℃, the top temperature of the distillation tower is 62 ℃, the operating pressure is 0.30MPa, the side-draw temperature is 75 ℃, and the backwashing ratio is 0.7; the washing water quantity/the quality of the material to be washed is 0.1, the operation temperature of the washing unit is 30 ℃, and the operation pressure is 0.12 MPa; the operation temperature of the water fractionating tower is 90 ℃, and the operation pressure is 0.12 MPa. The dearomatization rate is 91.8 percent, and the total yield is 96.5 percent.
Example 6
Raw materialsThe aromatic hydrocarbon content of the oil is 10.16 percent, the ratio of the raw oil entering the prefractionator 1 to the extraction tower 3 is 1:3, and the feed volume airspeed of the prefractionator is 1.5h-1The temperature at the bottom of the tower is 78 ℃, the temperature at the top of the tower is 64 ℃, and the operating pressure is 0.10 MPa; the space velocity of the feeding volume of the extraction tower is 0.35h-1The extracting agent is tetraethylene glycol, the solvent ratio (solvent feeding amount/extraction raw material amount) is 3.0, the operation temperature is 50 ℃, and the operation pressure is 0.22 MPa; the volume ratio of the stripping agent to the extraction oil is 1.8, the operating temperature of the stripping tower is 50 ℃, and the operating pressure is 0.22 MPa; the bottom temperature of the distillation tower is 90 ℃, the top temperature of the distillation tower is 64 ℃, the operating pressure is 0.40MPa, the side-draw temperature is 75 ℃, and the backwashing ratio is 0.7; the washing water quantity/the quality of the material to be washed is 0.1, the operation temperature of the washing unit is 30 ℃, and the operation pressure is 0.10 MPa; the operating temperature of the water fractionating tower is 120 ℃, and the operating pressure is 0.08 MPa. The dearomatization rate is 90.1 percent, and the total yield is 92.5 percent.
Example 7
The aromatic hydrocarbon content of the raw oil is 10.16 percent, the ratio of the raw oil entering the prefractionator 1 to the extraction tower 3 is 10:3, and the feed volume airspeed of the prefractionator is 1.5h-1The temperature at the bottom of the tower is 78 ℃, the temperature at the top of the tower is 64 ℃, and the operating pressure is 0.10 MPa; the space velocity of the feeding volume of the extraction tower is 0.35h-1The extracting agent is tetraethylene glycol, the solvent ratio (solvent feeding amount/extraction raw material amount) is 4.0, the operation temperature is 50 ℃, and the operation pressure is 0.22 MPa; the volume ratio of the stripping agent to the extraction oil is 2, the operating temperature of the stripping tower is 50 ℃, and the operating pressure is 0.22 MPa; the bottom temperature of the distillation tower is 90 ℃, the top temperature of the distillation tower is 64 ℃, the operating pressure is 0.40MPa, the side-draw temperature is 75 ℃, and the backwashing ratio is 0.7; the washing water quantity/the quality of the material to be washed is 0.1, the operation temperature of the washing unit is 30 ℃, and the operation pressure is 0.10 MPa; the operating temperature of the water fractionating tower is 120 ℃, and the operating pressure is 0.08 MPa. The dearomatization rate is 94.9 percent, and the total yield is 98.0 percent.
The present invention is capable of other embodiments, and various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (6)

1. A method for recovering aromatic hydrocarbon in low aromatic hydrocarbon content oil,the aromatic hydrocarbon content of the low aromatic hydrocarbon content oil is 5% -10.16%, and the method is characterized by comprising the following technological processes: performing prefractionation, extraction, back extraction, distillation, water washing, water fractionation and separation on raw oil to obtain a mixed aromatic hydrocarbon product, wherein the back extraction process is to perform back extraction on prefractionated benzene front fraction liquid and extract oil discharged from the bottom of an extraction tower (3) to obtain a reproducible and recyclable extractant and extract oil rich in aromatic hydrocarbon, and distilling the extract oil to obtain recyclable benzene front fraction liquid; the pre-fractionation process comprises the following steps: the raw oil lasts for 1.5h-1The volume space velocity of the pre-fractionating tower (1) is input into the pre-fractionating tower from the middle part of the pre-fractionating tower (1) for pre-fractionating, the operating temperature of the pre-fractionating tower (1) is 50-80 ℃, the operating pressure is 0.10-0.15MPa, the pre-fractionating tower top is discharged as a benzene front distillate, the benzene front distillate is cooled by a first condenser (2) and input into a back extractant storage tank (19), the benzene fraction is discharged from the tower bottom of the pre-fractionating tower (1) and enters an extraction tower (3) as an extraction raw material; the back extraction process comprises the following steps: the extraction oil discharged from the bottom of the extraction tower (3) is fed into the upper part of a stripping tower (4), a stripping agent, namely benzene front distillate is extracted from a stripping agent storage tank (19) and is input into the lower part of the stripping tower (4), the stripping agent and the extraction oil are subjected to liquid-liquid extraction, the volume ratio of the stripping agent to the extraction oil is 1-3, the operating temperature of the stripping tower (4) is 40-80 ℃, the operating pressure is 0.10-0.30MPa, the regenerated extraction agent is discharged from the bottom of the stripping tower (4), one part of the regenerated extraction agent is fed into the lower part of the stripping tower (4), the rest part of the regenerated extraction agent is input into an extraction agent storage tank (21), and the extraction oil rich in aromatic hydrocarbon is discharged from the top of the stripping tower; the water fractionation process comprises the following steps: the water phase discharged by the coalescence filter A10 is sent to a water fractionating tower (13) for distillation, the operation temperature of the water fractionating tower (13) is 85-120 ℃, the operation pressure is 0.05-0.15MPa, and the washing water quantity/substance to be washed mass ratio is 0.1-0.3; the water fractionating tower (13) separates water and the extractant in the feeding material to obtain the recyclable extractant which is discharged from the bottom of the water fractionating tower (13) and is input into an extractant storage tank (21).
2. The method for recovering aromatics from oils with low aromatics content as claimed in claim 1, wherein the extraction process comprises: the benzene distillation liquid discharged from the bottom of the prefractionator (1) is mixed with the uncut raw oilThen used as extraction feed for 0.35-0.53h-1The volume space velocity of the aromatic hydrocarbon is sent to the middle part of an extraction tower (3), an extraction solvent is extracted from an extractant storage tank (21) and is input to the upper part of the extraction tower (3), the extraction solvent and an extraction feed are subjected to liquid-liquid extraction, extraction oil rich in aromatic hydrocarbon and raffinate oil after the aromatic hydrocarbon is extracted are obtained after extraction, the volume ratio of the amount of the extraction solvent to the amount of the extraction feed is 1-5, the operation temperature of the extraction tower (3) is 40-80 ℃, the operation pressure is 0.10-0.30MPa, the extraction oil is discharged from the bottom of the extraction tower (3) and enters a stripping tower (4), and the raffinate oil is discharged from the top of the extraction tower (3).
3. The process for recovering aromatics in oils with low aromatics content as in claim 2, wherein the volume ratio of the amount of extraction solvent to the amount of extraction feed is 4.
4. The method of claim 2, wherein the extraction solvent is one of sulfolane, dimethyl sulfoxide, tetraethylene glycol, N-methylpyrrolidone, and N, N-dimethylformamide.
5. The method for recovering aromatics from oils with low aromatics content as claimed in claim 1, wherein the distillation process comprises: the extract oil rich in aromatic hydrocarbon is discharged from the top of the stripping tower (4), passes through heat exchangers (5, 6) and then is input into a distillation tower (7), the operating temperature of the distillation tower (7) is 50-100 ℃, and the operating pressure is 0.15-0.40 MPa; the liquid containing the benzene distillate extracted from the middle side line of the distillation tower (7) is pumped into the lower part of the extraction tower (3) to be used as a back washing liquid, and the amount of the back washing liquid/the amount of the extraction feed is 0.6-0.8; and the benzene front distillate is discharged from the top of the distillation tower (7), and is input into a back extractant storage tank (19) through a first heat exchanger (5), one part of mixed aromatic hydrocarbon discharged from the bottom of the distillation tower (7) is pumped back to the lower part of the distillation tower (7) through a second condenser (25), and the other part of the mixed aromatic hydrocarbon is sent into a feeding mixer B (28) through a fourth heat exchanger (17) for water washing to wash away the residual extractant in the mixed aromatic hydrocarbon.
6. The method for recovering aromatics from oils with low aromatics content as claimed in claim 1, wherein said separation process comprises: and (3) sending the mixed aromatic hydrocarbon at the bottom of the distillation tower (7) into a feed mixer B (28), washing with water to remove the residual extractant in the mixed aromatic hydrocarbon, sending the washed mixed aromatic hydrocarbon into a settling separator B (29) again to separate a water phase from an oil phase, inputting the oil phase into a coalescing filter B (30), and removing residual water and solvent to obtain a mixed aromatic hydrocarbon product (12) and raffinate oil (11).
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