A method for producing low-benzene gasoline

Abstract

A method for producing low-benzene gasoline comprises countercurrent contact of raw materials with a solvent to obtain a raffinate oil with a low benzene content and a first rich solvent. The raffinate oil is washed with water to obtain a first low-benzene gasoline and wash water. The first rich solvent is subjected to extractive distillation to obtain a second low-benzene gasoline and a second rich solvent. The second rich solvent is rectified to obtain an extracted oil and a lean solvent. The extracted oil is further rectified to obtain a benzene-rich fraction and a third low-benzene gasoline. Steam and an aqueous solvent obtained by stripping the wash water are respectively introduced into a solvent recovery tower. The first low-benzene gasoline, the second low-benzene gasoline, and the third low-benzene gasoline are collected to obtain low-benzene gasoline. The low-benzene gasoline obtained by this method has a yield of greater than 98% by mass and a benzene content of less than 0.15% by mass. The benzene content of the obtained benzene-rich fraction is greater than 90% by mass, and energy consumption is reduced by more than 15% compared to a conventional process of fractionation followed by extractive distillation.

Description

Technical Field

[0001] The present invention relates to a method for producing low-benzene gasoline, in particular to a method for producing low-benzene gasoline by removing benzene from full-fraction gasoline through a combined process of liquid-liquid extraction and extractive distillation. Background Art

[0002] With rising environmental awareness and the increasing severity of automobile exhaust pollution, environmental regulations are tightening restrictions on vehicle exhaust emissions. Because benzene is a carcinogen, incomplete combustion can increase pollutants in exhaust emissions, posing a threat to public health. Currently, international gasoline standards have reduced the volume fraction of benzene to ≤ 0.6%. Gasoline produced through the catalytic cracking process (referred to as catalytic gasoline) is a key component of gasoline. The volume fraction of benzene in this gasoline is approximately 0.85-1.5%. Separating the small amount of benzene from this fraction to ensure that the benzene content meets the increasingly stringent standards for gasoline products has become a pressing issue.

[0003] Compared to reformate, catalytic gasoline has a lower benzene content. Conventional aromatics extraction distillation (ED) technology requires prior fraction cutting. Even if a C6 fraction is obtained, its benzene content does not exceed 7% by mass. Furthermore, the raffinate oil, which accounts for over 93% by mass of the C6 fraction, must be evaporated to the top of the ED tower, resulting in high overall energy consumption. With traditional liquid-liquid extraction technology, a large amount of the raffinate oil requires water washing, which also increases the amount of water used for washing, resulting in higher energy consumption for purification and stripping in the water stripping and recovery towers. Furthermore, the increased water entering the recovery tower also makes it easier for the lean solvent at the bottom of the tower to evaporate to the top, necessitating increased reflux to ensure a solvent-free overhead, further increasing the energy consumption of the recovery tower.

[0004] For gasoline products, when using the liquid-liquid extraction process to separate benzene, the C7+ aromatics in the catalytic gasoline will also be separated, resulting in a loss of catalytic gasoline production and octane number. In addition, since the sulfur and nitrogen content in the catalytic gasoline raw materials is difficult to be lower than 1ppm, the separated C7+ aromatics cannot be directly put on the market as a product. Therefore, the traditional liquid-liquid extraction process is not suitable for the removal of benzene from catalytic gasoline. Summary of the Invention

[0005] The inventors discovered two key challenges in the solvent extraction debenzenization process for catalytic gasoline. The first is the broad feedstock fraction, necessitating process design and optimization to isolate only the benzene-rich fraction, minimizing hydrocarbon losses in the gasoline and ensuring the yield of low-benzene gasoline. The second key challenge is the low benzene content in the feedstock. The large amount of raffinate oil requires a significant amount of wash water to remove the solvent, resulting in the generation of a significant amount of stripping water and steam, necessitating the need to reduce the energy consumption of the system.

[0006] One of the objectives of the present invention is to address the characteristics of catalytic gasoline and the shortcomings of the prior art by providing a method for removing benzene from whole-fraction gasoline using a selective solvent to produce low-benzene gasoline. The present invention utilizes an extraction-first-then-cutting process to treat whole-fraction gasoline, significantly reducing the evaporation of hydrocarbons and lowering energy consumption. By designing an extractive distillation tower and a benzene fractionation tower, second and third low-benzene gasoline are obtained, significantly reducing hydrocarbon losses in gasoline and ensuring gasoline yield. Wash water is evaporated to the top of a water stripping tower to generate steam, which is then divided into two parts and introduced into a solvent recovery tower. The ratio of water stripping tower overhead steam to bottom solvent is optimized, further reducing energy consumption during the solvent recovery process. This production method has moderate operating conditions, a simple process, and no wastewater discharge. It can be integrated with existing catalytic cracking and S-zorb processes. The resulting low-benzene gasoline yield is greater than 98% by mass, with a benzene content less than 0.15% by mass. The resulting benzene-rich fraction has a benzene content greater than 90% by mass, and energy consumption is reduced by more than 15% compared to conventional fractionation-first-then-extractive distillation processes.

[0007] The method is characterized in that the production method is carried out in an apparatus comprising a solvent extraction tower 101, an extractive distillation tower 102, a water washing tower 103, a water stripping tower 104, a solvent recovery tower 105 and a benzene fraction tower 106;

[0008] The raw material 1 and the solvent 2 are countercurrently contacted in the solvent extraction tower 101 to obtain a raffinate oil 3 with a low benzene content and a first rich solvent 4;

[0009] The low-benzene raffinate oil 3 and the washing water 5 are introduced into the water washing tower 103, and washed with water to obtain the first low-benzene gasoline 6 and the washed water 7, and the washed water 7 enters the water stripping tower 104;

[0010] The first rich solvent 4 is introduced into the middle of the extractive distillation tower 102, and the solvent 12 is introduced into the extractive distillation tower 102, and extractive distillation is performed to obtain a second low-benzene gasoline 14 and a second rich solvent 16;

[0011] The second rich solvent 16 is introduced into the solvent recovery tower 105 and subjected to distillation to obtain extracted oil 18 and lean solvent 20;

[0012] The extracted oil 18 is introduced into the benzene fraction tower 106 and subjected to rectification to obtain a benzene-rich fraction 22 and a third low-benzene gasoline 24;

[0013] The washed water 7 is evaporated in a water stripping tower 104 to the top of the tower to obtain steam 8 which is introduced into a solvent recovery tower 105. The aqueous solvent 11 obtained at the bottom of the water stripping tower 104 enters the recovery tower 105.

[0014] The first low-benzene gasoline 6, the second low-benzene gasoline 14, and the third low-benzene gasoline 24 are collected to obtain low-benzene gasoline.

[0015] Another object of the present invention is to provide an apparatus for producing low-benzene gasoline, characterized in that the system comprises a solvent extraction tower 101, an extractive distillation tower 102, a water washing tower 103, a water stripping tower 104, a solvent recovery tower 105 and a benzene fractionation tower 106;

[0016] The solvent extraction tower 101 is connected to the extractive distillation tower 102 and the water washing tower 103 respectively; in the solvent extraction tower 101, the full-fraction gasoline is subjected to solvent extraction;

[0017] The extractive distillation tower 102 is also connected to the solvent recovery tower 105, and the extractive distillation tower 102 is used to process the first rich solvent;

[0018] The water washing tower 103 is connected to the reflux tank water bag of the solvent recovery tower 105 and the benzene fraction tower 106, and removes the raffinate oil from the solvent extraction tower 101 by water washing;

[0019] The water stripping tower 104 is connected to the water washing tower 103 and the solvent recovery tower 105 respectively, processes the washed water from the water washing tower 103, and uses the top steam as the solvent regeneration stripping gas of the solvent recovery tower 105;

[0020] The solvent recovery tower 105 processes the extracted oil from the extractive distillation tower 102 and recovers the solvent;

[0021] The benzene fraction tower 106 is connected to the solvent recovery tower 105 and is used to process the extracted oil obtained from the solvent recovery tower 105 . BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the process flow of the low-benzene gasoline production method provided by the present invention.

[0023] In the figure, there are a solvent extraction tower 101, an extractive distillation tower 102, a water washing tower 103, a water stripping tower 104, a solvent recovery tower 105 and a benzene fraction tower 106; a raw material 1, solvents 2 and 12, a lean solvent 20, a raffinate oil with a low benzene content 3, a first rich solvent 4, wash water 5, a first low-benzene gasoline 6, wash water 7, steam 8, middle stripping gas 9, bottom stripping gas 10, an aqueous solvent 11, a second low-benzene gasoline 13 and 14, a second rich solvent 16, extracted oil 17 and 18, water-in-water in a reflux tank 15, 19 and 23, a benzene-rich fraction 21 and 22, and a third low-benzene gasoline 24. DETAILED DESCRIPTION

[0024] The pressures described in this specification are all absolute pressures. The reflux ratio is the mass ratio of the reflux liquid flow rate returning to the tower from the top to the product flow rate at the top of the tower. The theoretical plates are numbered from top to bottom.

[0025] The present invention provides a method for producing low-benzene gasoline, characterized in that the production method is carried out in an apparatus comprising a solvent extraction tower 101, an extractive distillation tower 102, a water scrubber 103, a water stripping tower 104, a solvent recovery tower 105, and a benzene fractionation tower 106;

[0026] The raw material 1 and the solvent 2 are countercurrently contacted in the solvent extraction tower 101, and a raffinate oil 3 with a low benzene content and a first rich solvent 4 are obtained at the top of the tower;

[0027] The low-benzene content raffinate oil 3 and wash water 5 are introduced into a water washing tower 103, and washed with water to obtain a first low-benzene gasoline 6 and wash water 7, and the wash water 7 enters the water stripping tower 104;

[0028] The first rich solvent 4 is introduced into the middle of the extractive distillation tower 102, and the solvent 12 is introduced into the extractive distillation tower 102 to obtain a second low-benzene gasoline 14 and a second rich solvent 16 through extractive distillation.

[0029] The second rich solvent 16 is introduced into the solvent recovery tower 105 and subjected to rectification to obtain extracted oil 18 and lean solvent 20;

[0030] The extracted oil 18 is introduced into the benzene fraction tower 106 and subjected to rectification to obtain a benzene-rich fraction 22 and a third low-benzene gasoline 24;

[0031] The washed water 7 is evaporated in a water stripping tower 104 to the top of the tower to obtain steam 8 which is introduced into a solvent recovery tower 105. The aqueous solvent 11 obtained at the bottom of the water stripping tower 104 enters the recovery tower 105.

[0032] The first low-benzene gasoline 6, the second low-benzene gasoline 14, and the third low-benzene gasoline 24 are collected to obtain low-benzene gasoline.

[0033] In the method of the present invention, the steam 8 can enter the lower part of the solvent recovery tower 105 in its entirety, or it can be divided into two streams, a middle stripping gas 9 and a bottom stripping gas 10, which enter the middle and bottom parts of the solvent recovery tower 105, respectively. The mass ratio of the middle stripping gas 9 to the bottom stripping gas 10 is 0.05 to 2, preferably 0.1 to 1.5. The bottom stripping gas 10 serves as the stripping gas, and the middle stripping gas 9 can be used to supplement the heat of the solvent recovery tower, thereby reducing the consumption of heating steam at the bottom of the solvent recovery tower. Due to the high temperature at the bottom of the solvent recovery tower 105, the steam grade required is higher than that of the water stripping tower 104. By rationally allocating the mass ratio of the two steam streams 9 and 10 in the middle and bottom parts, the use of low-grade steam is increased while the consumption of high-grade steam is reduced, thereby achieving a reduction in overall energy consumption.

[0034] In the method of the present invention, the raw material is full-fraction gasoline, preferably FCC gasoline before desulfurization and nitrogen removal or a gasoline fraction with a boiling range of 60-200°C. The benzene content of the raw material is preferably 0.7-2% by mass, and the aromatics content is preferably 10-35% by mass.

[0035] In the solvent extraction tower 101 of the present invention, the solvent is selected from glycol or sulfone solvents, preferably sulfolane, diethylene glycol, triethylene glycol, tetraethylene glycol, or pentaethylene glycol. The solvent may also contain 0.5-3.0% by mass of water and 0.5-2.0% by mass of C9 or higher hydrocarbons. The solvent extraction tower 101 has a theoretical plate number of 5-20, a solvent to full-range gasoline mass ratio of 1-3, a tower top pressure of 0.1-1.0 MPa, a solvent inlet temperature of 60-100°C, a full-range gasoline inlet temperature of 30-60°C, and a tower bottom temperature of 30-90°C, preferably 40-80°C.

[0036] The extractive distillation tower 102 has a theoretical plate number of 10 to 20, a top pressure of 0.1 to 0.3 MPa, a bottom temperature of 150 to 190° C., a reflux ratio of 0.2 to 1.0, a mass ratio of the solvent 12 to the first rich solvent 4 of 0 to 0.2, preferably 0 to 0.1, and the solvent 12 is fed to the 2nd to 6th theoretical plates of the extractive distillation tower 102.

[0037] In water scrubber 103, the mass ratio of wash water 5 to the low-benzene raffinate 3 is no more than 0.15, preferably 0.1 to 0.15. The number of theoretical plates is 2 to 8, the top pressure is 0.1 to 0.8 MPa, and the top temperature is 50 to 80°C. In water scrubber 103, wash water 5 comes from the water-in-water tank 19 of the solvent recovery tower 105 and the water-in-water tank 23 of the benzene fractionation tower 106.

[0038] The water stripping tower 104 has 2 to 6 theoretical plates, a top pressure of 0.08 to 0.2 MPa, and a bottom temperature of 100 to 135°C. It uses 0.35 MPa steam as a heat source, or alternatively, 0.35 MPa steam and lean solvent 20 from the bottom of solvent recovery tower 105. The mass ratio of steam 8 obtained from the top of water stripping tower 104 to aqueous solvent 11 obtained from the bottom of the tower is 0.5 to 5, preferably 2 to 4.5.

[0039] The solvent recovery tower 105 has a theoretical plate number of 15 to 40, a reflux ratio of 0.3 to 1.0, a tower top pressure of 0.01 to 0.06 MPa, and a tower bottom temperature of 140 to 180°C, preferably 150 to 175°C. The second rich solvent 16 is fed from the middle and lower part of the solvent recovery tower 105, preferably at the Nth theoretical plate of the solvent recovery tower, where N is the total number of theoretical plates of the solvent recovery tower divided by 2, rounded to the nearest integer, plus 3 to 10. The feed position of the middle stripping gas (9) is 1 to 5 theoretical plates above the feed position of the second rich solvent (16). The feed position of the aqueous solvent 11 from the water stripping tower 104 is 1 to 10 theoretical plates above the feed position of the second rich solvent 16, so that the solvent brought into the gas phase due to the large amount of stripping gas can be absorbed into the liquid phase.

[0040] The benzene fraction tower 106 has a theoretical plate number of 10 to 30, a reflux ratio of 2.0 to 4.0, a top pressure of 0.05 to 1.0 MPa, and a bottom temperature of 120 to 160° C., preferably 125 to 150° C.

[0041] The method provided by the present invention may further include the steps of feeding the low-benzene gasoline into a desulfurization unit and feeding the benzene-rich fraction 22 into a pyrolysis gasoline hydrogenation unit, a reforming oil pre-hydrogenation unit, or serving as a feedstock for catalytic cracking or alkylation.

[0042] Another object of the present invention is to provide an apparatus for producing low-benzene gasoline, characterized in that the system comprises a solvent extraction tower 101, an extractive distillation tower 102, a water washing tower 103, a water stripping tower 104, a solvent recovery tower 105 and a benzene fractionation tower 106;

[0043] The solvent extraction tower 101 is connected to the extractive distillation tower 102 and the water washing tower 103 respectively; in the solvent extraction tower 101, the full-fraction gasoline is subjected to solvent extraction;

[0044] The extractive distillation tower 102 is also connected to the solvent recovery tower 105, and the extractive distillation tower 102 is used to process the first rich solvent;

[0045] The water washing tower 103 is connected to the reflux tank water bag of the solvent recovery tower 105 and the benzene fraction tower 106, and removes the raffinate oil from the solvent extraction tower 101 by water washing;

[0046] The water stripping tower 104 is connected to the water washing tower 103 and the solvent recovery tower 105 respectively, processes the washed water from the water washing tower 103, and uses the top steam as the solvent regeneration stripping gas of the solvent recovery tower 105;

[0047] The solvent recovery tower 105 processes the extracted oil from the extractive distillation tower 102 and recovers the solvent;

[0048] The benzene fraction tower 106 is connected to the solvent recovery tower 105 and is used to process the extracted oil obtained from the solvent recovery tower 105 .

[0049] The present invention will be further described below with reference to the accompanying drawings.

[0050] Figure 1 In the process, feedstock 1 (e.g., FCC gasoline) enters the lower portion of solvent extraction tower 101, while solvent 2 enters the upper portion. After extraction, raffinate 3 with a low benzene content is discharged from the top of solvent extraction tower 101 and enters the lower portion of water scrubber 103. First rich solvent 4, obtained at the bottom of solvent extraction tower 101, enters the middle portion of extractive distillation tower 102. A small stream of solvent 12 enters the upper portion of extractive distillation tower 102. A stream consisting primarily of light non-aromatic hydrocarbons is obtained at the top of the tower, a portion of which is refluxed as second low-benzene gasoline 13, and the remainder as second low-benzene gasoline 14. Water 15 from the reflux tank water bag enters water stripping tower 104. Second rich solvent 16, obtained at the bottom of extractive distillation tower 102, enters the lower and middle portion of solvent recovery tower 105. Extracted oil is obtained at the top of solvent recovery tower 105, a portion of which 17 is refluxed, while the remaining 18 enters benzene fractionation tower 106. Water 19 and 23 from the reflux drum are combined and then used as wash water 5 to enter the upper portion of water scrubber 103. Lean solvent 20 is discharged from the bottom of solvent recovery tower 105 and can be used as a partial heat source for water stripping tower 104 (well known to those skilled in the art, not shown in the accompanying drawings). After heat exchange, it is split into two streams, solvent 2 and solvent 12, for recycling. Steam 8 from the top of water stripping tower 104 is split into two streams, steam 9 and steam 10, respectively, entering the middle and bottom of solvent recovery tower 105. Aqueous solvent 11 at the bottom of water stripping tower 104 enters solvent recovery tower 105. A portion of the benzene-rich fraction 21 obtained at the top of benzene fraction column 106 is refluxed, while the remaining benzene-rich fraction 22 is discharged from the device. Water 23 in the reflux drum is combined with water 19 to form wash water 5 and enter the upper portion of water scrubber 103. The heavier third low-benzene gasoline 24 at the bottom of benzene fraction column 106 is combined with the first low-benzene gasoline 6 and the second low-benzene gasoline 14 to exit the device as the low-benzene gasoline product. Wash water 5 and low-benzene raffinate oil 3 are countercurrently contacted within water scrubber 103. The washed raffinate oil is combined with the second low-benzene gasoline 14 as the first low-benzene gasoline 6 and exit the device. Wash water 7 is combined with water 15 to enter the water stripping column 104.

[0051] The present invention is further described below by way of examples, but the present invention is not limited thereto.

[0052] Example 1

[0053] This example follows Figure 1The gasoline fraction obtained from the FCC stabilizer tower was debenzenized using the following process. The feedstock properties are shown in Table 1. The solvent was sulfolane. The main operating conditions for each tower are shown in Table 2. The water stripping tower 104 used 0.35 MPa steam and lean solvent 20 as heat sources, while the other towers all used 1.0 MPa steam as heat sources. Debenzenization performance and energy consumption are shown in Table 3.

[0054] Example 2

[0055] This example follows Figure 1 The process is used to remove benzene from the gasoline fraction obtained from the stabilizer tower of the FCC unit.

[0056] The raw material properties are shown in Table 1. The solvent is triethylene glycol. The main operating parameters of each tower are shown in Table 2. Water stripping tower 104 uses 0.35 MPa steam and lean solvent 20 as the heat source, benzene fraction tower 106 uses 0.35 MPa steam as the heat source, and the other towers all use 1.0 MPa steam as the heat source. The debenzenization effect and energy consumption are shown in Table 3.

[0057] Example 3

[0058] This example follows Figure 1 The process is used to remove benzene from the gasoline fraction obtained from the stabilizer tower of the FCC unit.

[0059] The raw materials were the same as in Example 2, and the solvent was triethylene glycol. The main operating parameters of each tower are shown in Table 2. Water stripping tower 104 used 0.35 MPa steam and lean solvent 20 as the heat source, benzene fraction tower 106 used 0.35 MPa steam as the heat source, and the other towers all used 1.0 MPa steam as the heat source. The debenzenization effect and energy consumption are shown in Table 3.

[0060] Comparative Example 1

[0061] The raw materials were the same as those in Example 1. The raw materials were first fractionated to obtain a C6 fraction and the remaining fractions. The C6 fraction was then subjected to extractive distillation to remove benzene to obtain a debenzened C6 fraction and a benzene-rich fraction. The debenzened C6 fraction was mixed with the remaining fractions to obtain low-benzene gasoline. The extractive distillation solvent was sulfolane. 1.0 MPa steam was used as the heat source. The main operating conditions are shown in Table 4. The debenzening effect and energy consumption are shown in Table 3.

[0062] Comparative Example 2

[0063] The raw materials were the same as those in Example 2. The raw materials were first fractionated to obtain a C6 fraction and the remaining fractions. The C6 fraction was then subjected to extractive distillation to remove benzene to obtain a debenzened C6 fraction and a benzene-rich fraction. The debenzened C6 fraction was mixed with the remaining fractions to obtain low-benzene gasoline. The extractive distillation solvent was triethylene glycol, and 1.0 MPa steam was used as the heat source. The main operating conditions are shown in Table 4, and the debenzening effect and energy consumption are shown in Table 3.

[0064] Table 1

[0065] Raw material properties Example 1, Comparative Example 1 Raw materials Examples 2, 3, and Comparative Example 2 Raw materials Group composition, mass % Alkanes 32.93 33.65 Cycloalkanes 6.03 6.12 Olefins 35.71 34.13 Aromatics 25.33 26.10 total 100 100 Benzene content, mass% 0.88 1.40

[0066] Table 2

[0067]

[0068]

[0069]

[0070] Table 3

[0071]

[0072] As shown in Tables 2 and 3, compared with Example 2, Example 3 reduces the bottom temperature of water stripping column 104 and injects all the stripping gas from the bottom of solvent recovery column 105, resulting in higher energy consumption to achieve the same separation results. Compared with Example 1 and Comparative Example 1, and with Examples 2 and 3 and Comparative Example 2, under the premise of consistent benzene content in the low-benzene gasoline product, the method of the present invention achieves higher quality yield of low-benzene gasoline, lower energy consumption, and higher benzene enrichment in the benzene-rich fraction, compared with the process of fractionation and cutting followed by extractive distillation.

[0073] Table 4

[0074]

[0075]

Claims

1. A method for producing low-benzene gasoline, characterized in that The production method is carried out in a device comprising a solvent extraction tower (101), an extractive distillation tower (102), a water washing tower (103), a water stripping tower (104), a solvent recovery tower (105) and a benzene fraction tower (106); The raw material and the solvent are countercurrently contacted in the solvent extraction tower (101) to obtain a raffinate oil (3) with a low benzene content and a first rich solvent (4); The low-benzene raffinate oil (3) and washing water (5) are introduced into a water washing tower (103), and washed with water to obtain a first low-benzene gasoline (6) and washed water (7), and the washed water (7) enters the water stripping tower (104); The first rich solvent (4) is introduced into the extractive distillation tower (102), and the solvent is introduced into the extractive distillation tower (102), and a second low-benzene gasoline (14) and a second rich solvent (16) are obtained through extractive distillation; The second rich solvent (16) is introduced into the solvent recovery tower (105) and subjected to distillation to obtain extracted oil (18) and lean solvent (20); The extracted oil (18) is introduced into the benzene fraction tower (106) and subjected to rectification to obtain a benzene-rich fraction (22) and a third low-benzene gasoline (24); The washed water (7) is evaporated in a water stripping tower (104) to the top of the tower to obtain steam (8) which is introduced into a solvent recovery tower (105); the aqueous solvent (11) obtained at the bottom of the water stripping tower (104) enters the solvent recovery tower (105); The first low-benzene gasoline (6), the second low-benzene gasoline (14), and the third low-benzene gasoline (24) are collected to obtain low-benzene gasoline; The raw material is full-fraction gasoline.

2. The method according to claim 1, characterized in that The steam (8) is divided into two streams, namely the middle stripping gas (9) and the bottom stripping gas (10), which enter the middle and bottom of the solvent recovery tower (105) respectively.

3. The method according to claim 2, characterized in that The mass ratio of the middle stripping gas (9) to the bottom stripping gas (10) is 0.05-2.

4. The method according to claim 2, characterized in that The mass ratio of the middle stripping gas (9) to the bottom stripping gas (10) is 0.1-1.

5.

5. The method according to claim 1, characterized in that The full-fraction gasoline is FCC crude gasoline or a gasoline fraction with a boiling range of 60-200°C.

6. The method according to claim 1, wherein In the solvent extraction tower (101), the solvent is selected from one or more of sulfolane, diethylene glycol, triethylene glycol, tetraethylene glycol or pentaethylene glycol.

7. The method according to claim 6, wherein The solvent contains 0.5-3.0% by mass of water and 0.5-2.0% by mass of C9 and above hydrocarbons.

8. The method according to claim 1, wherein The solvent extraction tower (101) has a top pressure of 0.1-1.0 MPa, a bottom temperature of 30-90° C., and a mass ratio of solvent to full-fraction gasoline of 1-3.

9. The method according to claim 1, wherein The solvent extraction tower (101) has a top pressure of 0.1-1.0 MPa, a bottom temperature of 40-80° C., and a mass ratio of solvent to full-fraction gasoline of 1-3.

10. According to the method of claim 1, the top pressure of the extractive distillation tower (102) is 0.1~0.3MPa, the bottom temperature is 150~190℃, the reflux ratio is 0.2~1.0, the number of theoretical plates is 10~20, the mass ratio of the solvent to the first rich solvent in the extractive distillation tower (102) is 0.04~0.2, and the feed position of the solvent is the 2nd to 6th theoretical plates of the extractive distillation tower (102).

11. The method according to claim 1, wherein In the water washing tower (103), the mass ratio of the washing water (5) to the raffinate oil (3) with a low benzene content does not exceed 0.

15.

12. The method according to claim 11, wherein The mass ratio of the washing water (5) to the raffinate oil (3) with low benzene content is 0.1 to 0.

15.

13. The method according to claim 1, wherein: In the water washing tower (103), the washing water (5) comes from the water-in-water of the reflux tank of the solvent recovery tower (105) and the water-in-water of the reflux tank of the benzene fraction tower (106).

14. The method according to claim 1, wherein The water stripping tower (104) has a top pressure of 0.08-0.2 MPa and a bottom temperature of 100-135°C. 0.35 MPa steam is used as a heat source, or 0.35 MPa steam is used as a heat source through heat exchange with the lean solvent (20) at the bottom of the solvent recovery tower (105).

15. The method according to claim 1, wherein the mass ratio of the steam (8) obtained at the top of the water stripping tower (104) to the water-containing solvent (11) obtained at the bottom of the tower is 0.5-5.

16. The method according to claim 1, wherein The solvent recovery tower (105) has a theoretical plate number of 15 to 40, a reflux ratio of 0.3 to 1.0, a tower top pressure of 0.01 to 0.06 MPa, and a tower bottom temperature of 140 to 180°C.

17. The method according to claim 1, wherein The solvent recovery tower (105) has a theoretical plate number of 15-40, a reflux ratio of 0.3-1.0, a tower top pressure of 0.01-0.06 MPa, and a tower bottom temperature of 150-175°C.

18. The method according to claim 1, characterized in that The feeding position of the second rich solvent (16) is the Nth theoretical plate of the solvent recovery tower (105), where N is the total number of theoretical plates of the solvent recovery tower divided by 2 and rounded up plus 3 to 10.

19. The method according to claim 2, characterized in that The feed position of the middle stripping gas (9) is located 1 to 5 theoretical plates above the feed position of the second rich solvent (16).

20. The method according to claim 1, wherein In the solvent recovery tower (105), the feed position of the aqueous solvent (11) from the water stripping tower (104) is located 1 to 10 theoretical plates above the feed position of the second rich solvent (16).

21. The method according to claim 1, wherein In the solvent recovery tower (105), the feed position of the aqueous solvent (11) is located above the feed position of the steam (8).

22. The method according to claim 1, wherein The benzene fraction tower (106) has a theoretical plate number of 10 to 30, a reflux ratio of 2.0 to 4.0, a tower top pressure of 0.05 to 1.0 MPa, and a tower bottom temperature of 120 to 160°C.

23. The method according to claim 1, wherein The benzene fraction tower (106) has a theoretical plate number of 10 to 30, a reflux ratio of 2.0 to 4.0, a tower top pressure of 0.05 to 1.0 MPa, and a tower bottom temperature of 125 to 150°C.

24. The method according to claim 1, characterized in that The low-benzene gasoline enters the desulfurization unit; the benzene-rich fraction (22) enters the pyrolysis gasoline hydrogenation unit, the reforming oil pre-hydrogenation unit or serves as a catalytic cracking or alkylation raw material.

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