CN117089366A

CN117089366A - Method for separating heavy aromatic hydrocarbon from kerosene fraction

Info

Publication number: CN117089366A
Application number: CN202210516456.8A
Authority: CN
Inventors: 高思亮; 唐文成; 田龙胜; 赵明; 郄思远; 庞伟伟
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2022-05-12
Filing date: 2022-05-12
Publication date: 2023-11-21

Abstract

A process for separating heavy aromatic hydrocarbon from kerosene fraction includes such steps as liquid-liquid extraction of raw material, optional main solvent and cosolvent in extraction tower, distillation of tower top stream, and water washing. And (3) back-extracting the tower bottom rich solvent and recovering the solvent to obtain a heavy aromatic product. The selective main solvent has high selectivity to heavy aromatic hydrocarbon and strong dissolving power. The method can obtain heavy aromatic products with purity higher than 99wt% and yield higher than 95wt%, realize internal recycling of multiple streams and have no sewage discharge.

Description

Method for separating heavy aromatic hydrocarbon from kerosene fraction

Technical Field

The present invention relates to a process for separating heavy aromatics from kerosene fractions. In particular to a method for separating heavy aromatics in kerosene by utilizing a selective solvent and a cosolvent liquid-liquid extraction.

Background

Under the influence of new global epidemic situation, the global commercial passenger traffic is greatly reduced, and the consumption of aviation kerosene (aviation kerosene for short) also presents similar trend. Wood Mackenzie corporation in the european oil refining technical conference report in 2020 indicated that european gasoline and diesel demand would slowly return to 2019 levels from 2020 to 2022, but aviation kerosene to 2022 quarter 4 would still be expected to be more than 10% lower than 2019 demand levels. Gao Chengda Jeff Currie, a commodity research director, indicates that the new coronal pneumonia epidemic will have a lasting effect on the behavior of global enterprises and that the aviation kerosene requirements are unlikely to be completely restored.

Aviation kerosene is usually derived from the normally first-line kerosene fraction obtained from atmospheric and vacuum distillation of crude oil, and this kerosene fraction contains a large amount of paraffins and is an effective heavy cracking feedstock. However, this kerosene fraction also contains about 30wt% of aromatic hydrocarbons, although the aromatic hydrocarbon content can be reduced to 5 to 10wt% by further hydrofinishing. According to the reaction principle of preparing ethylene by steam cracking, different hydrocarbon cracking products have certain difference, and arene cracking only has dehydrogenation reaction, so that alkane products cannot be generated, and the operation period is seriously influenced. Thus, separating out this part of the aromatics in the kerosene fraction for the production of high value-added carbon materials, while the remainder for steam cracking is an effective solution to the problem of aviation kerosene export and to the benefit improvement of refineries.

The method for removing aromatic hydrocarbon from petroleum distillate mainly comprises solvent extraction. When the raw material is C6-C8 fraction, sulfolane is generally used as solvent, and the corresponding separation process is liquid-liquid extraction or extractive distillation, so as to obtain the triphenyl product (i.e. benzene, toluene and xylene). When the boiling range of the raw material is higher, the dissolving capacity of sulfolane to heavy aromatic hydrocarbon is obviously reduced, and the separation requirement is difficult to meet. CN87107146a discloses a method for extracting aromatic hydrocarbon in diesel oil fraction by using double solvents, the boiling range of the diesel oil fraction is 300-530 ℃, the first solvent is furfural, phenol, sulfoxide and dimethyl pyrrolidone, preferably furfural, and the second solvent is light oil. The boiling point range of the solvent is far lower than that of the raw material, so that the solvent can be recovered by flash evaporation and steam stripping. However, the method cannot realize the recycling of stripping steam, so that a large amount of solvent (furfural) wastewater is generated, the energy consumption is high, the solvent loss is serious, and the method is not friendly to the environment. The method can obtain heavy aromatic hydrocarbon with purity higher than 95wt percent, and the aromatic hydrocarbon extraction rate is 50-95 wt percent.

US4333824 uses N-methylpyrrolidone as a solvent to extract aromatics from lubricating oils to make lubricating oil base oils. Because the difference between the boiling point range of the solvent and the boiling point range of aromatic hydrocarbon is smaller, the method designs the flow of low-pressure distillation, high-pressure distillation, vacuum flash evaporation and steam stripping to recover the solvent in the extracted oil, and adopts the flow of vacuum flash evaporation and steam stripping to recover the solvent in the raffinate oil, besides, a solvent purification system (not described in detail) is further arranged to further purify the solvent, so that the process is complex. Finally, the volume yield of the extracted oil is 10-70%, and the purity of heavy aromatic hydrocarbon in the extracted oil is 80wt%.

CN101921624a discloses a method for preparing high-quality diesel oil by extracting and hydrogenating combination process, wherein the boiling range of the raw oil is 160-389 ℃, and the extracting solvent is one of sulfolane, N-methylpyrrolidone and dimethyl sulfoxide. The method realizes the separation of the solvent and the raffinate oil by water washing, and adopts the processes of back extraction, water washing and rectification to realize the separation of the solvent and the heavy aromatic hydrocarbon, but no back extraction agent is disclosed. The purity of the finally obtained heavy aromatics is 90-92 wt%, and the yield is about 80wt%.

There is currently no method for efficiently separating heavy aromatics from kerosene fractions with low energy consumption and environmental protection.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide the method capable of effectively separating heavy aromatic hydrocarbon from the kerosene fraction, which not only improves the added value of the kerosene fraction, but also provides a more economic way for aviation kerosene and improves the economic benefit.

The invention provides a method for separating heavy aromatic hydrocarbon from kerosene fraction, which is characterized in that the method comprises the steps of contacting raw kerosene fraction with selective main solvent and cosolvent in an extraction tower for liquid-liquid extraction, distilling and washing first raffinate oil obtained from the top of the extraction tower to obtain raffinate oil products, and stripping and recovering rich solvent obtained from the bottom of the extraction tower to obtain heavy aromatic hydrocarbon products.

The invention separates heavy aromatic hydrocarbon from kerosene fraction by using selective main solvent and cosolvent, the selective main solvent has higher selectivity and higher solubility to heavy aromatic hydrocarbon, the cosolvent can improve the purity of heavy aromatic hydrocarbon and reduce the difficulty of solvent recovery process, and the heavy aromatic hydrocarbon product with purity higher than 99wt% and yield higher than 95wt% can be obtained by extraction-back extraction-rectification combined process. The raffinate oil obtained by extracting, distilling and washing the kerosene fraction raw material can be used as industrial white oil (II) or steam cracking raw material, wherein the aromatic hydrocarbon content is reduced to not higher than 0.2wt%.

Compared with the prior art, the separation method has the following characteristics:

(1) The selectivity main solvent has high selectivity to heavy aromatic hydrocarbon and strong dissolving power, the purity of the obtained heavy aromatic hydrocarbon product is higher than 99wt percent, and the yield is higher than 95wt percent;

(2) The solvent content in the raffinate oil and the heavy aromatic hydrocarbon is not more than 10ppm by adopting the high boiling point solvent and the separation process matched with the high boiling point solvent, and no wastewater is discharged.

(3) The process has mild operation condition, can be used for removing aromatic hydrocarbon in the kerosene fraction, has no hydrogen consumption and low energy consumption, and obviously reduces the aromatic hydrocarbon content in the kerosene fraction.

Drawings

FIG. 1 is a schematic diagram of a process for separating heavy aromatics from kerosene fraction using a selective solvent and a co-solvent according to the present invention.

Detailed Description

The invention is further described in detail below by means of the figures and examples. The features and advantages of the present invention will become more apparent from the description. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.

The word "exemplary" is used herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are illustrated in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

In addition, the technical features described below in the different embodiments of the present invention may be combined with each other as long as they do not collide with each other.

Two key problems are the separation of heavy aromatics from kerosene fractions, namely, the solvent selectivity and the solvent solubility are difficult to be compatible. The conventionally used aromatic hydrocarbon extraction solvents (such as sulfolane and tetraethylene glycol) have poor solubility to C8-C12 heavy aromatic hydrocarbon, the yield of the heavy aromatic hydrocarbon is low, and a considerable amount of heavy aromatic hydrocarbon still exists in raffinate oil, so that the raffinate oil is not a good cracking raw material; the solvents such as N-methyl pyrrolidone and N-formyl morpholine have better solubility to heavy aromatic hydrocarbon, but have poor selectivity, so that the finally obtained raffinate oil has low yield and the purity of the heavy aromatic hydrocarbon in the extract oil is low. Secondly, because the boiling point of heavy aromatic hydrocarbon is high, the boiling point of the heavy aromatic hydrocarbon is relatively close to or even completely overlapped with that of conventionally used aromatic hydrocarbon extraction solvents (such as N-formylmorpholine and N-methylpyrrolidone), and the separation of the solvent and the aromatic hydrocarbon is difficult to realize by a rectification method. In order to ensure the purity of the circulating solvent, various methods such as water washing, back extraction, steam stripping and the like are needed, so that the energy consumption is high and the process is complex; if a low boiling point solvent (such as acetonitrile, methanol, etc.) is used, on the one hand, the selectivity of the solvent is poor, and on the other hand, all the solvent needs to be evaporated, and the energy consumption is high. According to the invention, alkyl sulfolane is used as a selective main solvent, so that the solubility of the selective main solvent to heavy aromatic hydrocarbon is greatly improved on the premise of ensuring high selectivity to the heavy aromatic hydrocarbon, and the yield of the heavy aromatic hydrocarbon is ensured; the purity of heavy aromatic hydrocarbon is further improved by adding cosolvent C5-C7 saturated hydrocarbon, and the difficulty of the solvent recovery process is reduced; the selective main solvent, the cosolvent and the water are circulated through the extraction-back extraction-rectification combined process, so that the solvent loss is reduced, the energy consumption is reduced, and the environmental pollution is avoided.

In the present invention, the term "normal line" refers to the fraction of the normal pressure distillation apparatus side line in the petroleum industry.

Specifically, the method for separating heavy aromatic hydrocarbon from kerosene fraction provided by the invention comprises the following steps:

(1) Feeding kerosene fraction raw material into a solvent extraction tower from the middle lower part, selectively feeding main solvent into the extraction tower from the top, and injecting cosolvent C5-C7 saturated hydrocarbon from the bottom of the extraction tower; the first raffinate oil is obtained at the top of the extraction tower, and the rich solvent is obtained at the bottom of the extraction tower;

(2) The first raffinate oil obtained from the top of the extraction tower enters a raffinate oil distillation tower, a C5-C7 saturated hydrocarbon stream is separated from the top of the raffinate oil distillation tower, and a second raffinate oil is obtained from the tower kettle; the second raffinate oil enters a water washing tower, the solvent is removed and then is taken as a raffinate oil product to be discharged from the top of the water washing tower, and the water after washing of the water washing tower enters a water stripping tower;

(3) The rich solvent obtained at the bottom of the extraction tower enters the top of the back extraction tower, and the C5-C7 saturated hydrocarbon stream enters the lower part of the back extraction tower; the material flow rich in heavy aromatic hydrocarbon and C5-C7 saturated hydrocarbon obtained from the back extraction tower top enters the middle part of an aromatic hydrocarbon recovery tower, and solvent is recovered through rectification; C5-C7 saturated hydrocarbon material flow is obtained at the top of the aromatic hydrocarbon recovery tower, and heavy aromatic hydrocarbon products are obtained at the bottom of the tower;

(4) The main solvent containing C5-C7 saturated hydrocarbon obtained at the bottom of the back extraction tower enters a solvent recovery tower, a C5-C7 saturated hydrocarbon material flow is obtained at the top of the tower, and the lean solvent obtained at the bottom of the tower is recycled to the extraction tower to be used as a selective main solvent;

(5) The C5-C7 saturated hydrocarbon material flows obtained from the top of the raffinate oil distillation tower, the aromatic hydrocarbon recovery tower and the solvent recovery tower are divided into two parts, one part enters the bottom of the cosolvent extraction tower, and the other part enters the lower part of the back extraction tower; the water stripping tower top material flow enters a condenser at the top of the raffinate oil distillation tower, and solvent-containing water generated at the tower bottom enters the bottom of the solvent recovery tower; the water in the reflux drum water drum at the top of the solvent recovery tower is returned to the water washing tower as washing water.

In an embodiment of the invention, the selective main solvent is selected from alkyl sulfolanes, preferably 3-methyl sulfolane and/or 2, 4-dimethyl sulfolane. The selective main solvent may contain 0.5wt% to 3.0wt% of water and/or 0 to 1.0wt% of hydrocarbon compound. In an embodiment of the present invention, the cosolvent is a C5 to C7 saturated hydrocarbon, preferably one or more selected from the group consisting of C6 raffinate oil, n-hexane, n-heptane.

In an embodiment of the present invention, in step (1) of the method, the mass ratio of the selective main solvent to the kerosene fraction raw material is 3:1 to 7:1, and the mass ratio of the cosolvent C5-C7 saturated hydrocarbon to the kerosene fraction raw material is 0.2 to 0.6; the feeding temperature of the selective main solvent is 80-180 ℃, preferably 90-140 ℃, the pressure of the top of the extraction tower is 0.2-0.7 MPa absolute pressure, and the theoretical plate number is 8-15.

In an embodiment of the invention, in the step (2) of the method, the theoretical plate number of the raffinate oil distillation column is 10-30, the reflux ratio is 0.2-2, the tower top pressure is 0.1-0.5 MPa absolute pressure, and the tower bottom temperature is 150-250 ℃.

In an embodiment of the present invention, in step (2) of the method, the mass ratio of the water washing water of the water washing column to the second raffinate oil is 0.1 to 0.5, preferably 0.1 to 0.3, the water washing column top pressure is 0.4MPa to 0.7MPa absolute, and the water washing temperature is 30 ℃ to 50 ℃.

In an embodiment of the invention, in step (3) of the process, the theoretical plate number of the stripping column is 8-12, the column top pressure is 0.2-0.8 MPa absolute, the C5-C7 saturated hydrocarbon stream is fed into the column at a temperature of 40-100 ℃, and the mass ratio of the C5-C7 saturated hydrocarbon stream to the rich solvent is 0.05-0.5, preferably 0.07-0.15.

In an embodiment of the present invention, in step (3) of the method, the theoretical plate number of the aromatic hydrocarbon recovery column is 15 to 40, the reflux ratio is 0.2 to 2, the column top pressure is 0.1MPa to 0.5MPa absolute pressure, and the column bottom temperature is 150 ℃ to 300 ℃.

In an embodiment of the present invention, in step (4) of the method, the theoretical plate number of the solvent recovery column is 5 to 30, the reflux ratio is 0.3 to 1.0, the column top pressure is 0.05MPa to 0.15MPa absolute, and the column bottom temperature is 150 to 200 ℃, preferably 160 to 180 ℃.

In the embodiment of the invention, the kerosene fraction raw material of the present invention is preferably derived from the normal line after hydrofining, wherein the sulfur and nitrogen contents are not more than 1ppm respectively, the boiling range is 140-250 ℃, and the mass fraction of heavy aromatics is 3-30 wt%.

The method can obtain heavy aromatic products with purity higher than 99wt% and yield higher than 95wt%, realize internal recycling of multiple streams and have no sewage discharge.

The invention is further described below with reference to fig. 1.

In FIG. 1, kerosene fraction feedstock enters the lower portion of extraction column 101 via line 1, fresh selective main solvent and/or recycled lean solvent enters the upper portion of column 101 via line 2, fresh and/or recycled co-solvent C5-C7 saturated hydrocarbons enter the bottom of column 101 via line 25, and the first raffinate obtained from the top of column 101 enters raffinate distillation column 102 via line 3. The C5-C7 saturated hydrocarbon flow obtained from the top of the tower 102 enters a condenser and a reflux tank through a pipeline 4, part of the C5-C7 saturated hydrocarbon returns to the tower 102 through a pipeline 5, and the rest is gathered into a pipeline 25 through a pipeline 6 and returns to the bottom of the tower 101. 102, the second raffinate oil obtained from the bottom of the tower enters the lower part of a water washing tower 103 through a pipeline 7, water washing water enters the upper part of the tower 103 through a pipeline 8, a raffinate oil product obtained after water washing is discharged from the top of the tower 103 through a pipeline 9 and water after water washing enters a water stripping tower 104 through a pipeline 10. The stream distilled from the top of the column 104 is merged with the line 4 before entering the condenser at the top of the column 102 through the line 11, and the solvent-containing water obtained from the bottom of the column 104 enters the bottom of the solvent recovery column 107 through the line 12.

The rich solvent obtained from the bottom of the extraction tower 101 enters the upper part of the back extraction tower 105 through a pipeline 13, the C5-C7 saturated hydrocarbon enters the lower part of the back extraction tower 105 through a pipeline 14, and the heavy aromatic hydrocarbon-rich material obtained from the top of the back extraction tower 105 enters an aromatic hydrocarbon recovery tower 106 through a pipeline 15. C5-C7 saturated hydrocarbon obtained from the top of the 106 tower flows through a pipeline 16 to enter a condenser and a reflux tank, part of the saturated hydrocarbon returns to the 106 tower through a pipeline 17, the rest of the saturated hydrocarbon enters a pipeline 18, and heavy aromatic hydrocarbon obtained from the tower bottom is discharged out of the device through a pipeline 19.

The material flow rich in C5-C7 saturated hydrocarbon and main solvent obtained at the bottom of the tower 105 enters a solvent recovery tower 107 through a pipeline 20, the C5-C7 saturated hydrocarbon obtained at the top of the tower 107 enters a condenser and a reflux tank through a pipeline 21, part of the material flow returns to the tower 107 through a pipeline 22, the rest of the material flow is converged with a pipeline 18 through a pipeline 23, part of the material flow is separated and enters the bottom of the tower 105 through a pipeline 14, the rest of the material flow is converged with a pipeline 6 through a pipeline 24, and the material flow is finally returned to the bottom of the tower 101 through a pipeline 25.

The top reflux drum water of columns 102, 106, 107 are each joined by line 26, 27, 28 to line 8 and returned as wash water to the top of the wash column 103.

The invention is further illustrated by the following examples, but is not limited thereto.

Example 1

In this example, heavy aromatics in the hydrofined kerosene fraction were separated according to the scheme of FIG. 1, the raw material boiling range was 144℃to 230℃and the composition was shown in Table 1. The selective main solvent is 3-methyl sulfolane, the cosolvent is C6 raffinate oil, the main operating conditions of each tower are shown in Table 2, and the purity and yield of heavy aromatic products are shown in Table 4.

Example 2

In this example, heavy aromatics in the hydrofined kerosene fraction were separated according to the procedure of FIG. 1, the raw material composition was the same as in example 1, the selective main solvent was 2, 4-dimethyl sulfolane, the cosolvent was n-hexane, the main operating conditions of each column were shown in Table 2, and the purity and yield of the heavy aromatics were shown in Table 4.

Example 3

In this example, heavy aromatics in the hydrofined kerosene fraction were separated according to the procedure of FIG. 1, the raw material composition was the same as in example 1, the selective main solvent was 3-methyl sulfolane, the cosolvent was n-heptane, the main operating conditions of each column were shown in Table 2, and the purity and yield of the heavy aromatics were shown in Table 4.

Comparative example 1

The comparative example is carried out according to the flow of figure 1 to separate heavy aromatics from hydrofined kerosene fraction, the raw material composition is the same as in example 1, the selective main solvent is N-methylpyrrolidone, the cosolvent is C6 raffinate oil, the main operating conditions of each tower are shown in Table 2, and the purity and yield of the heavy aromatics are shown in Table 4.

As can be seen from Table 4, compared with comparative example 1, the heavy aromatic hydrocarbon product obtained by the method of the present invention has the advantages of higher yield, significantly improved purity, greatly reduced aromatic hydrocarbon content in the raffinate oil product, and favorable subsequent steam cracking.

Comparative example 2

The heavy aromatic hydrocarbon in the hydrofined kerosene fraction is separated according to the conventional aromatic hydrocarbon liquid extraction process, the raw materials are subjected to extraction tower and raffinate oil water washing tower to obtain raffinate oil products after aromatic hydrocarbon removal, the rich solvent at the bottom of the extraction tower enters a stripping tower, the light component obtained at the top of the stripping tower returns to the extraction tower as a counter-washing liquid, and the material flow at the bottom of the stripping tower enters a solvent recovery tower to be separated to obtain solvent and aromatic hydrocarbon. The raw material composition is the same as that of example 1, the solvent is sulfolane, the main operating conditions of each tower are shown in Table 3, and the purity and yield of the heavy aromatic hydrocarbon product are shown in Table 4.

As can be seen from Table 4, compared with comparative example 2, the heavy aromatic hydrocarbon product obtained by the method of the present invention has the advantages of higher purity, significantly improved yield, greatly reduced aromatic hydrocarbon content in the raffinate oil product, and favorable subsequent steam cracking.

TABLE 1

Kerosene fraction composition	Mass fraction (wt%)
		Paraffin hydrocarbons	44.9
Cycloalkane (CNS)	51.1
		Total aromatic hydrocarbon	4.0
Totalizing	100

TABLE 2

TABLE 3 Table 3

TABLE 4 Table 4

In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "inner", "outer", "front", "rear", "left", "right", etc. are directions or positional relationships based on the operation state of the present invention are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements to be referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention.

The invention has been described above in connection with preferred embodiments, which are, however, exemplary only and for illustrative purposes. On this basis, the invention can be subjected to various substitutions and improvements, and all fall within the protection scope of the invention.

Claims

1. A method for separating heavy aromatic hydrocarbon from kerosene fraction is characterized by that the raw material of kerosene fraction is contacted with selective main solvent and cosolvent in extraction tower to make liquid-liquid extraction, the first raffinate oil obtained from the top of extraction tower is undergone the processes of distillation and water washing to obtain raffinate oil product, and the rich solvent obtained from the bottom of extraction tower is undergone the processes of back extraction and solvent recovery to obtain heavy aromatic hydrocarbon product.

2. The process according to claim 1, wherein the selective main solvent is an alkyl sulfolane, preferably 3-methyl sulfolane and/or 2, 4-dimethyl sulfolane.

3. The method according to claim 1 or 2, wherein the co-solvent is a C5-C7 saturated hydrocarbon, preferably one or more selected from the group consisting of C6 raffinate oil, n-hexane, n-heptane.

4. A process according to any one of claims 1 to 3, wherein the selective main solvent contains 0.5 to 3.0wt% water and/or 0 to 1.0wt% hydrocarbons.

5. The method according to any one of claims 1 to 4, wherein the kerosene fraction raw material enters the extraction column from the middle lower part of the extraction column, the selective main solvent enters the extraction column from the top of the extraction column, the cosolvent is injected into the bottom of the extraction column, the first raffinate oil is obtained from the top of the extraction column, and the rich solvent is obtained from the bottom of the extraction column.

6. The method according to any one of claims 1 to 5, wherein the mass ratio of the selective main solvent to the kerosene fraction raw material entering the extraction column is 3:1 to 7:1, the mass ratio of the cosolvent to the kerosene fraction raw material is 0.2 to 0.6, the temperature of the selective main solvent entering the extraction column is 80 to 180 ℃, preferably 90 to 140 ℃, the pressure of the top of the extraction column is 0.2 to 0.7MPa absolute, and the theoretical plate number is 8 to 15.

7. The process of any one of claims 1 to 6, wherein the first raffinate is fed to a raffinate distillation column for distillation, a flux of co-solvent is obtained at the top of the column, the second raffinate obtained at the bottom of the column is fed to a water wash column, the solvent is removed and fed as raffinate product from the top of the water wash column, and the washed water from the water wash column is fed to a water stripper.

8. The process of claim 7 wherein the theoretical plates of the raffinate distillation column are 10 to 30, the reflux ratio is 0.2 to 2, the column top pressure is 0.1MPa to 0.5MPa absolute, and the column bottom temperature is 150 ℃ to 250 ℃.

9. The process according to claim 7, wherein the mass ratio of the aqueous wash water of the aqueous wash column to the second raffinate oil is from 0.1 to 0.5, preferably from 0.1 to 0.3, the top pressure of the aqueous wash column is from 0.4MPa to 0.7MPa absolute and the temperature of the aqueous wash is from 30 ℃ to 50 ℃.

10. The method according to any one of claims 1 to 9, wherein the rich solvent obtained from the bottom of the extraction tower enters the top of the stripping tower, the cosolvent flow enters the lower part of the stripping tower, the heavy aromatic hydrocarbon and cosolvent-enriched flow obtained from the top of the stripping tower enters the aromatic hydrocarbon recovery tower from the middle part for rectification and solvent recovery, the cosolvent flow is obtained from the top of the aromatic hydrocarbon recovery tower, and the heavy aromatic hydrocarbon product is obtained from the bottom of the aromatic hydrocarbon recovery tower.

11. The process according to claim 10, wherein the theoretical number of plates in the stripping column is 8-12, the column top pressure is 0.2-0.8 MPa absolute, the temperature of the co-solvent stream flowing into the column is 40-100 ℃, and the mass ratio of the co-solvent stream to the rich solvent is 0.05-0.5, preferably 0.07-0.15.

12. The method of claim 10, wherein the theoretical plates of the aromatic recovery tower are 15-40, the reflux ratio is 0.2-2, the pressure at the top of the tower is 0.1-0.5 MPa absolute, and the temperature at the bottom of the tower is 150-300 ℃.

13. The process of claim 10 wherein the co-solvent-containing selective main solvent obtained at the bottom of the stripping column is fed to a solvent recovery column, a co-solvent stream is obtained at the top of the column, and the lean solvent obtained at the bottom of the column is recycled to the extraction column as selective main solvent.

14. The method of claim 13, wherein the theoretical plates of the solvent recovery column are 5 to 30, the reflux ratio is 0.3 to 1.0, the pressure at the top of the column is 0.05 to 0.15MPa absolute, and the temperature at the bottom of the column is 150 to 200 ℃.

15. The method of claim 13, wherein the cosolvent stream obtained from the raffinate distillation column, the aromatic recovery column, and the solvent recovery column top is split into two streams, one stream being fed as the cosolvent to the bottom of the extraction column, and the other stream being fed as the cosolvent stream to the lower portion of the stripping column; the water stripping tower top material flow enters a condenser at the top of the raffinate oil distillation tower, and solvent-containing water generated at the tower bottom enters the bottom of the solvent recovery tower; the water in the reflux drum water drum at the top of the solvent recovery tower is returned to the water washing tower as washing water.

16. The method of claim 1, wherein the kerosene fraction feedstock is derived from a normal line after hydrofinishing, wherein the sulfur and nitrogen content is not more than 1ppm, the boiling range is 140 ℃ to 250 ℃, and the mass fraction of heavy aromatics is 3wt% to 30wt%, respectively.