CN115074160A

CN115074160A - Benzene washing system

Info

Publication number: CN115074160A
Application number: CN202210802970.8A
Authority: CN
Inventors: 李景民; 黄巧芳; 周凌云; 陈博东; 王善增; 刘洋; 蒋洪海; 何卫国; 撖伟
Original assignee: SGIS Songshan Co Ltd
Current assignee: SGIS Songshan Co Ltd
Priority date: 2022-07-07
Filing date: 2022-07-07
Publication date: 2022-09-20
Anticipated expiration: 2042-07-07
Also published as: CN115074160B

Abstract

The invention discloses a benzene washing system, wherein a coal gas inlet is formed in the bottom of a first benzene washing tower, the top of the first benzene washing tower is communicated with the bottom of a second benzene washing tower through a coal gas pipeline, a coal gas outlet is formed in the top of the second benzene washing tower, an oil inlet in the top of the second benzene washing tower is communicated with an oil-poor pipe, the bottom of the second benzene washing tower is communicated with the top of the first benzene washing tower through a semi-rich oil pipe, an oil outlet is formed in the bottom of the first benzene washing tower, the oil-poor pipe is provided with an oil-poor heat exchanger, the oil-poor heat exchanger is provided with a first outlet through which a first cooling medium flows out, the semi-rich oil pipe is provided with a semi-rich heat exchanger, the semi-rich heat exchanger is provided with a first inlet and a second inlet, the first inlet is communicated with the first outlet through a first pipeline, and the second inlet is used for introducing a second cooling medium. The first cooling medium flowing out of the lean oil heat exchanger is introduced into the semi-rich oil heat exchanger for heat supplement, so that the existing surplus heat can be directly secondarily utilized, and the cost of washing the benzene with the coal gas is reduced.

Description

Benzene washing system

Technical Field

The invention relates to the field of coal gas purification, in particular to a benzene washing system.

Background

Crude benzene is used as a byproduct in the coking process, has the characteristics of insolubility in water, flammability, explosiveness, easy poisoning and the like, and is a mixture consisting of various organic matters. The crude benzene can be synthesized into acetone, phenol, etc. The crude benzene is refined into toluene, xylene, pure benzene and other products, which are important chemical raw materials. The crude benzene in the coke oven gas can be recovered to purify the coke oven gas, so that the crude benzene with more economic value can be obtained. The current method for recovering crude benzene with the highest cost performance is a wash oil absorption method.

Referring to fig. 1, the coal gas from the final cooling tower enters from the bottom of the first benzene washing tower 1 ', is discharged from the top of the first benzene washing tower 1', then enters the bottom of the second benzene washing tower 2 ', and is discharged from the top of the second benzene washing tower 2'. The lean oil is cooled by a lean oil heat exchanger 3 ', then sent to the top of a second benzene washing tower 2' to be sprayed, reversely contacted with the coal gas, the lean oil absorbs benzene in the coal gas and then is converted into semi-rich oil, the semi-rich oil flows out from the bottom of the second benzene washing tower 2 'and then is conveyed to the top of a first benzene washing tower 1' to be sprayed, the semi-rich oil absorbs benzene in the coal gas and then is converted into rich oil, and the rich oil flows out from the bottom of the first benzene washing tower 1 'and then is sent to a distillation system through a rich oil pump 5' to be debenzolized.

Because the temperature in the second benzene washing tower 2 'is higher, in order to ensure the absorption effect of the semi-rich oil to benzene in the first benzene washing tower 1', the semi-rich oil needs to be cooled to 25 ℃ by using the semi-rich oil heat exchanger 4 'before being introduced into the first benzene washing tower 1'.

When the environmental temperature is higher than 25 ℃ in summer, the heat dissipation capacity of the semi-rich heat exchanger 4 ' is small, the semi-rich heat exchanger 4 ' can be cooled by low-temperature water (16 ℃) to promote the heat dissipation of semi-rich oil, however, when the environmental temperature is lower than 25 ℃ in rainy weather (or low-temperature weather in winter), the heat dissipation capacity of the semi-rich heat exchanger 4 ' is large, the cooling temperature of the semi-rich oil is greatly reduced, so that under the state that the low-temperature water is not introduced, the semi-rich oil temperature is still lower than 25 ℃, the semi-rich oil temperature is lower than the gas temperature after final cooling, the rich oil carries water, the process stability of a crude benzene distillation system is damaged, and the gas benzene washing efficiency is reduced. And when the temperature of the semi-rich oil is lower than 25 ℃, the liquidity of the semi-rich oil is deteriorated, so that slag is easily accumulated in the semi-rich oil heat exchanger 4' to block, the flow of circulating washing oil is reduced, the temperature of the semi-rich oil is forced to be increased, the washing oil is finally influenced to absorb benzene in the coal gas, and the benzene washing effect is deteriorated.

Disclosure of Invention

The embodiment of the invention aims to: provided is a benzene washing system which can reduce the temperature fluctuation of semi-rich oil and improve the benzene washing effect.

In order to achieve the purpose, the invention adopts the following technical scheme:

the benzene washing system comprises a first benzene washing tower, a second benzene washing tower, a lean oil pipe and a semi-rich oil pipe, wherein a coal gas inlet is formed in the bottom of the first benzene washing tower, the top of the first benzene washing tower is communicated with the bottom of the second benzene washing tower through a coal gas pipeline, a coal gas outlet is formed in the top of the second benzene washing tower, an oil inlet in the top of the second benzene washing tower is communicated with the lean oil pipe, the bottom of the second benzene washing tower is communicated with the top of the first benzene washing tower through the semi-rich oil pipe, an oil outlet is formed in the bottom of the first benzene washing tower, the lean oil pipe is provided with a lean oil heat exchanger, a flowing first cooling medium is arranged in the lean oil heat exchanger, a first outlet for flowing out of the first cooling medium is formed in the lean oil heat exchanger, the semi-rich oil pipe is provided with a semi-rich oil heat exchanger, and a first inlet and a second inlet are formed in the semi-rich oil heat exchanger, the first inlet is communicated with the first outlet through a first pipeline, the second inlet is used for introducing a second cooling medium, and the temperature of the second cooling medium is lower than that of the first cooling medium in the first pipeline.

As a preferred scheme of the benzene washing system, the semi-rich oil heat exchanger comprises a heat exchanger body and a first distribution box, a first chamber, a second chamber and a third chamber are arranged in the first distribution box, the third chamber is communicated with the first chamber and the second chamber respectively, the first inlet is formed in the wall of the first chamber, the second inlet is formed in the wall of the second chamber, the second outlet is formed in the wall of the third chamber, and the second outlet is communicated with the inlet of the heat exchanger body.

As a preferable scheme of the benzene washing system, the first chamber and the third chamber are communicated through a first one-way valve, and the first cooling medium in the first chamber flows into the third chamber through the first one-way valve;

the second chamber is communicated with the third chamber through a second one-way valve, and the second cooling medium in the second chamber flows into the third chamber through the second one-way valve.

As a preferable scheme of the benzene washing system, the semi-rich heat exchanger further includes a second distribution tank, a fourth chamber, a fifth chamber and a sixth chamber are provided in the second distribution tank, a third inlet is provided on a cavity wall of the fourth chamber, the third inlet is communicated with an outlet of the heat exchanger body, a third outlet and a fourth outlet are respectively provided on cavity walls of the fifth chamber and the sixth chamber, the fourth chamber is communicated with the fifth chamber through a third check valve, the fourth chamber is communicated with the sixth chamber through a fourth check valve, a cooling medium in the fourth chamber flows into the fifth chamber through the third check valve, and a cooling medium in the fourth chamber flows into the sixth chamber through the fourth check valve.

As a preferable scheme of the benzene washing system, a first valve is arranged on the first pipeline, and a second valve is arranged at the second inlet.

As a preferred scheme of the benzene washing system, the benzene washing system comprises a remote control module, and the remote control module is electrically connected with the first valve and the second valve respectively.

As a preferable scheme of the benzene washing system, a temperature sensor is arranged on the semi-rich oil pipe, the temperature sensor is used for detecting the temperature of the semi-rich oil entering the first benzene washing tower, and the temperature sensor is electrically connected with the remote control module.

As a preferable scheme of the benzene washing system, a cooling heat exchanger is further arranged on the lean oil pipe, and the cooling heat exchanger is located between the lean oil heat exchanger and the second benzene washing tower.

As a preferable scheme of the benzene washing system, the temperature of the third cooling medium flowing in the cooling heat exchanger is lower than that of the first cooling medium.

As a preferable scheme of the benzene washing system, a third outlet of the semi-rich oil heat exchanger is communicated with the lean oil heat exchanger through a second pipeline, and a cooler is arranged on the second pipeline.

The invention has the beneficial effects that: when the environment temperature is low, the heat dissipation capacity of the semi-rich oil heat exchanger is large, the first cooling medium can supplement heat for the semi-rich oil heat exchanger, so that the temperature of semi-rich oil entering the first benzene washing tower can be in a proper temperature range, when the environment temperature is high, the heat dissipation capacity of the semi-rich oil heat exchanger is small, the second cooling medium can be only introduced into the semi-rich oil heat exchanger, and the temperature of the semi-rich oil entering the first benzene washing tower is not too high; the first cooling medium flowing out of the lean oil heat exchanger is introduced into the semi-rich oil heat exchanger for heat supplement, so that the existing surplus heat can be directly secondarily utilized, and the cost of washing the benzene with the coal gas is reduced.

Drawings

The invention is explained in more detail below with reference to the figures and examples.

FIG. 1 is a schematic diagram of a benzene-washing system according to the prior art.

FIG. 2 is a schematic diagram of a benzene washing system according to an embodiment of the present invention.

Fig. 3 is a schematic view of a first distribution box according to an embodiment of the present invention.

In FIG. 1:

1', a first benzene washing tower; 2', a second benzene washing tower; 3', a lean oil heat exchanger; 4', a semi-rich oil heat exchanger; 5', an oil-rich pump;

in fig. 2 to 3:

1. a first benzene washing tower; 101. (ii) a 102. (ii) a 2. A second benzene washing tower; 201. (ii) a 202. (ii) a 3. A lean oil heat exchanger; 4. a semi-rich oil heat exchanger; 41. a heat exchanger body; 42. a first distribution box; 421. a first chamber; 422. a second chamber; 423. a third chamber; 424. a first check valve; 425. a second one-way valve; 426. a first inlet; 427. a second inlet; 428. a second outlet; 43. a second distribution box; 5. a first pipeline; 6. a first valve; 7. a second valve; 8. a third valve; 9. a fourth valve; 10. a remote control module; 11. a gas pipe; 12. a semi-rich tubing; 13. a lean oil pipe; 14. a semi-rich pump; 15. cooling the heat exchanger; 16. an oil-rich pump.

Detailed Description

In order to make the technical problems solved, technical solutions adopted and technical effects achieved by the present invention clearer, the technical solutions of the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, unless expressly stated or limited otherwise, the terms "connected," "connected," and "fixed" are to be construed broadly, e.g., as meaning permanently connected, removably connected, or integral to one another; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

As shown in fig. 2 and 3, the benzene washing system provided by the present invention comprises a first benzene washing tower 1, a second benzene washing tower 2, a lean oil pipe 13 and a semi-rich oil pipe 12, wherein the bottom of the first benzene washing tower 1 is provided with a gas inlet, the top of the first benzene washing tower 1 is communicated with the bottom of the second benzene washing tower 2 through a gas pipe 11, the top of the second benzene washing tower 2 is provided with a gas outlet, the oil inlet at the top of the second benzene washing tower 2 is communicated with the lean oil pipe 13, the bottom of the second benzene washing tower 2 is communicated with the top of the first benzene washing tower 1 through the semi-rich oil pipe 12, the bottom of the first benzene washing tower 1 is provided with an oil outlet, the lean oil pipe 13 is provided with the lean oil heat exchanger 3, the lean oil heat exchanger 3 is provided with a flowing first cooling medium, the lean oil heat exchanger 3 is provided with a first outlet for flowing out of the first cooling medium, the semi-rich oil pipe 12 is provided with the semi-rich oil heat exchanger 4, the semi-rich oil pipe 4 is provided with a first inlet 426 and a second inlet 427, the first inlet 426 is connected to the first outlet via the first pipe 5, and the second inlet 427 is used for introducing a second cooling medium, the temperature of which is lower than the temperature of the first cooling medium in the first pipe 5. In the embodiment, coal gas is introduced from a coal gas inlet at the bottom of the first benzene washing tower 1, flows out from the top of the first benzene washing tower 1, enters the bottom of the second benzene washing tower 2 through a coal gas pipeline 11, and finally flows out from a coal gas outlet at the top of the second benzene washing tower 2, the coal gas and the lean oil and the semi-rich oil flow in opposite directions, and because the temperature in the second benzene washing tower 2 is higher, the temperature of the semi-rich oil flowing out from the second benzene washing tower 2 is higher than 28 ℃, the semi-rich oil heat exchanger 4 can cool the semi-rich oil, so that the temperature of the semi-rich oil introduced into the first benzene washing tower 1 is in the temperature range of 25-28 ℃. In this embodiment, the rich oil flowing out of the second benzene washing tower 2 is sent to the distillation system through the rich oil pump 16 for debenzolization to obtain lean oil, the lean oil is re-injected into the second benzene washing tower 2 through the lean oil pipe 13 to realize the recycling of the lean oil, and the temperature of the lean oil obtained by debenzolization in the distillation system is high (about 105 ℃), so that the lean oil needs to be cooled by using the lean oil heat exchanger 3 to ensure that the temperature of the lean oil introduced from the oil inlet at the top of the second benzene washing tower 2 is within the temperature range of 25 ℃ to 28 ℃. In this embodiment, the first cooling medium and the lean oil perform heat exchange in the lean oil heat exchanger 3, so that the temperature of the first cooling medium flowing out of the lean oil heat exchanger 3 is high, the temperature of the first cooling medium is 80-90 ℃, the temperature of the second cooling medium is about 16 ℃, when the ambient temperature is low, the heat dissipation capacity of the semi-rich oil heat exchanger 4 is large, the first cooling medium can supplement heat to the semi-rich oil heat exchanger 4, so that the temperature of the semi-rich oil entering the first benzene scrubber 1 can be within a temperature range of 25-28 ℃, when the ambient temperature is high, the heat dissipation capacity of the semi-rich oil heat exchanger 4 is small, at this time, the second cooling medium can be only introduced into the semi-rich oil heat exchanger 4, and the temperature of the semi-rich oil entering the first benzene scrubber 1 is ensured to be not higher than 28 ℃; the first cooling medium flowing out of the lean oil heat exchanger 3 is introduced into the semi-rich oil heat exchanger 4 for heat supplement, so that the existing surplus heat can be directly secondarily utilized, and the cost of washing the benzene with the coal gas is reduced.

Specifically, the semi-rich heat exchanger 4 includes a heat exchanger body 41 and a first distribution box 42, a first chamber 421, a second chamber 422 and a third chamber 423 are provided in the first distribution box 42, the third chamber 423 is respectively communicated with the first chamber 421 and the second chamber 422, a wall of the first chamber 421 is provided with a first inlet 426, a wall of the second chamber 422 is provided with a second inlet 427, a wall of the third chamber 423 is provided with a second outlet 428, and the second outlet 428 is communicated with the inlet of the heat exchanger body 41. Through setting up first chamber 421, second chamber 422 and third chamber 423, when injecting first cooling medium and second cooling medium into half rich oil heat exchanger 4 simultaneously, first cooling medium and second cooling medium can be fully mixed in third chamber 423 for the cooling medium temperature that lets in heat exchanger body 41 is even, improves the heat transfer effect.

In the present embodiment, the first cooling medium and the second cooling medium are both cooling water, and the first cooling medium and the second cooling medium have the same composition and differ only in temperature.

In an embodiment, the first valve 6 is disposed at the first inlet 426, the second valve 7 is disposed at the second inlet 427, and the first valve 6 and the second valve 7 are disposed to control the amounts of the first cooling medium and the second cooling medium, so as to control the temperature of the semi-rich oil entering the first benzene washing tower 1, when the ambient temperature is higher, the first valve 6 may be closed, the semi-rich oil is cooled only by the second cooling medium, and when the ambient temperature is lower, the first valve 6 may be opened, so that the first cooling medium flowing out of the lean oil heat exchanger 3 heats the semi-rich oil heat exchanger 4, and the temperature of the semi-rich oil is ensured.

Specifically, the benzene washing system comprises a remote control module 10, and the remote control module 10 is electrically connected with the first valve 6 and the second valve 7 respectively. By providing the remote control module 10, the operation of the first valve 6 and the second valve 7 can be remotely controlled, and the workload of workers can be reduced.

Specifically, the semi-rich oil pipe 12 is provided with a temperature sensor, the temperature sensor is used for detecting the temperature of the semi-rich oil entering the first benzene washing tower 1, and the temperature sensor is electrically connected with the remote control module 10. By providing a temperature sensor, the remote control module 10 may call manual adjustment of the first valve 6 and the second valve 7 when the temperature sensor detects that the temperature of the semi-rich oil deviates from the temperature range of 25 ℃ to 28 ℃, and of course, the program may be set so that the remote control module 10 may also automatically control the first valve 6 and the second valve 7.

In one embodiment, the first cooling medium and the second cooling medium have different compositions, and in order to avoid mixing of the first cooling medium and the second cooling medium, the first chamber 421 and the third chamber 423 are communicated through the first check valve 424, and the first cooling medium in the first chamber 421 flows into the third chamber 423 through the first check valve 424; the second chamber 422 and the third chamber 423 are communicated with each other through a second check valve 425, and the second cooling medium in the second chamber 422 flows into the third chamber 423 through the second check valve 425. When the ambient temperature is high, the heat dissipation capacity of the semi-rich heat exchanger 4 is small, and only the second cooling medium needs to exchange heat with the semi-rich oil, at this time, the first valve 6 is closed, the second valve 7 is opened, the second cooling medium enters the second chamber 422 from the second inlet 427 and then enters the third chamber 423 through the second check valve 425, because the first check valve 424 is arranged between the third chamber 423 and the first chamber 421, the second cooling medium cannot enter the first chamber 421, and the second cooling medium can only flow into the heat exchanger body 41 through the second outlet 428 of the third chamber 423; when the ambient temperature is low, the heat exchanger body 41 needs to be heated, at this time, the first valve 6 is opened, the second valve 7 is closed, the first cooling medium flowing out of the first outlet of the lean oil heat exchanger 3 flows into the first chamber 421 from the first inlet 426, and flows into the third chamber 423 through the first check valve 424, because the second check valve 425 is arranged between the third chamber 423 and the second chamber 422, the first cooling medium cannot enter the second chamber 422, and the first cooling medium can only flow into the heat exchanger body 41 through the second outlet 428 of the third chamber 423, so that the temperature of the heat exchanger body 41 is raised, and the temperature of the semi-rich oil is prevented from being too low; when the first cooling medium is introduced into the first chamber 421, the pressure in the third chamber 423 is increased, the second one-way valve 425 is automatically closed, the residual second cooling medium in the second chamber 422 cannot enter the third chamber 423, and the mixing of the first cooling medium and the second cooling medium to influence the water quality when the second cooling medium is introduced into the second chamber 422 is further avoided.

In this embodiment, the semi-rich heat exchanger 4 further includes a second distribution tank 43, a fourth chamber, a fifth chamber and a sixth chamber are disposed in the second distribution tank 43, a third inlet is disposed on a wall of the fourth chamber, the third inlet is communicated with the outlet of the heat exchanger body 41, a third outlet and a fourth outlet are disposed on walls of the fifth chamber and the sixth chamber, respectively, the fourth chamber is communicated with the fifth chamber through a third check valve, the fourth chamber is communicated with the sixth chamber through a fourth check valve, the cooling medium in the fourth chamber flows into the fifth chamber through the third check valve, the cooling medium in the fourth chamber flows into the sixth chamber through the fourth check valve, a third valve 8 is disposed at the third outlet, a fourth valve 9 is disposed at the fourth outlet, and the third valve 8 and the fourth valve 9 are electrically connected to the remote control module 10, respectively. When the ambient temperature is high, only a second cooling medium needs to be introduced into the semi-rich oil heat exchanger 4, at this time, the first valve 6 and the third valve 8 are closed, the second valve 7 and the fourth valve 9 are opened, and when the ambient temperature is low, the first cooling medium is required to heat the heat exchanger body 41, at this time, the first valve 6 and the third valve 8 are opened, and the second valve 7 and the fourth valve 9 are closed, so that the mixing of the first cooling medium and the second cooling medium can be avoided, the first cooling medium and the second cooling medium can respectively flow out from different outlets, and the recovery processing of the first cooling medium and the second cooling medium is facilitated; in this embodiment, the first inlet 426, the second inlet 427, the third inlet, the second outlet 428, the third outlet and the fourth outlet are all provided with flanges, which facilitates the fixed connection between the pipelines.

Specifically, a cooling heat exchanger 15 is further provided on the lean oil pipe 13, and the cooling heat exchanger 15 is located between the lean oil heat exchanger 3 and the second benzene-washing column 2. In this embodiment, the lean oil has a high temperature (about 105 ℃), and the lean oil is difficult to be cooled to a temperature in the range of 25 ℃ to 28 ℃ only by the lean oil heat exchanger 3, and the lean oil can be further cooled by the cooling heat exchanger 15, so that the temperature of the lean oil fed into the second benzene washing tower 2 is ensured to be in the range of 25 ℃ to 28 ℃.

Specifically, in the present embodiment, the temperature of the third cooling medium flowing in the cooling heat exchanger 15 is about 16 ℃.

Specifically, a third outlet of the semi-rich heat exchanger 4 is communicated with the lean oil heat exchanger 3 through a second pipeline, and a cooler is arranged on the second pipeline. Through setting up half rich oil heat exchanger 4 and lean oil heat exchanger 3 of second pipeline intercommunication, can realize the used circulation of first coolant, in this embodiment, let in the first coolant normal temperature of lean oil heat exchanger 3, first coolant's temperature is about 25 ℃, can reduce first coolant's temperature to the normal atmospheric temperature through the heat dissipation of second pipeline pipe wall self, also can carry out supplementary heat dissipation to first coolant through the cooler. When the first valve 6 is closed, the first cooling medium can flow directly to the second line.

Specifically, a semi-rich pump 14 is provided on the semi-rich pipe 12. By arranging the semi-rich oil pump 14, flowing power can be provided for semi-rich oil in the semi-rich oil pipe 12, so that the semi-rich oil in the semi-rich oil pipe 12 can flow to the top of the first benzene washing tower 1; set up half rich oil pump 14, can reduce the degree of difficulty of arranging of first benzene scrubber 1 and second benzene scrubber 2, for example, can arrange first benzene scrubber 1 and second benzene scrubber 2 on the coplanar, do not have the height restriction between first benzene scrubber 1 and the second benzene scrubber 2.

In the description herein, it is to be understood that the terms "upper," "lower," "left," "right," and the like are based on the orientation or positional relationship shown in the drawings for convenience in description and simplicity of operation, and do not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered limiting of the present invention. Furthermore, the terms "first" and "second" are used merely for descriptive purposes and are not intended to have any special meaning.

In the description herein, references to the description of "an embodiment," "an example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example.

Furthermore, it should be understood that although the specification describes embodiments, not every embodiment includes only a single embodiment, and such description is for clarity purposes only, and it will be understood by those skilled in the art that the specification as a whole and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

The technical principles of the present invention have been described above with reference to specific embodiments. The description is made for the purpose of illustrating the principles of the invention and should not be construed in any way as limiting the scope of the invention. Based on the explanations herein, those skilled in the art will be able to conceive of other embodiments of the present invention without inventive effort, which would fall within the scope of the present invention.

Claims

1. A benzene washing system comprises a first benzene washing tower, a second benzene washing tower, a lean oil pipe and a semi-rich oil pipe, wherein a coal gas inlet is formed in the bottom of the first benzene washing tower, the top of the first benzene washing tower is communicated with the bottom of the second benzene washing tower through a coal gas pipeline, a coal gas outlet is formed in the top of the second benzene washing tower, an oil inlet in the top of the second benzene washing tower is communicated with the lean oil pipe, the bottom of the second benzene washing tower is communicated with the top of the first benzene washing tower through the semi-rich oil pipe, an oil outlet is formed in the bottom of the first benzene washing tower, the lean oil pipe is provided with a lean oil heat exchanger, a flowing first cooling medium is arranged in the lean oil heat exchanger, a first outlet for flowing out of the first cooling medium is formed in the lean oil heat exchanger, and the semi-rich oil pipe is provided with a semi-rich oil heat exchanger, and is characterized in that the semi-rich oil heat exchanger is provided with a first inlet and a second inlet, the first inlet is communicated with the first outlet through a first pipeline, the second inlet is used for introducing a second cooling medium, and the temperature of the second cooling medium is lower than that of the first cooling medium in the first pipeline.

2. The benzene washing system of claim 1, wherein the semi-rich heat exchanger comprises a heat exchanger body and a first distribution box, a first chamber, a second chamber and a third chamber are arranged in the first distribution box, the third chamber is respectively communicated with the first chamber and the second chamber, the first inlet is arranged on the wall of the first chamber, the second inlet is arranged on the wall of the second chamber, the second outlet is arranged on the wall of the third chamber, and the second outlet is communicated with the inlet of the heat exchanger body.

3. The benzene washing system according to claim 2, wherein the first chamber and the third chamber are communicated through a first check valve, and the first cooling medium in the first chamber flows into the third chamber through the first check valve;

4. The benzene washing system according to claim 2, wherein the semi-rich heat exchanger further comprises a second distribution tank, a fourth chamber, a fifth chamber and a sixth chamber are arranged in the second distribution tank, a wall of the fourth chamber is provided with a third inlet, the third inlet is communicated with the outlet of the heat exchanger body, a wall of each of the fifth chamber and the sixth chamber is provided with a third outlet and a fourth outlet, the fourth chamber is communicated with the fifth chamber through a third check valve, the fourth chamber is communicated with the sixth chamber through a fourth check valve, the cooling medium in the fourth chamber flows into the fifth chamber through the third check valve, and the cooling medium in the fourth chamber flows into the sixth chamber through the fourth check valve.

5. The benzene washing system of claim 1, wherein the first pipeline is provided with a first valve, and the second inlet is provided with a second valve.

6. The benzene washing system of claim 5, comprising a remote control module electrically connected to the first valve and the second valve, respectively.

7. The benzene washing system of claim 6, wherein the semi rich oil pipe is provided with a temperature sensor for detecting the temperature of the semi rich oil entering the first benzene washing tower, and the temperature sensor is electrically connected with the remote control module.

8. The benzene washing system of claim 1, wherein the lean oil pipe is further provided with a cooling heat exchanger, and the cooling heat exchanger is located between the lean oil heat exchanger and the second benzene washing tower.

9. The benzene washing system of claim 8, wherein the temperature of the third cooling medium flowing within the cooling heat exchanger is lower than the temperature of the first cooling medium.

10. The benzene washing system of claim 1, wherein the third outlet of the semi-rich heat exchanger is communicated with the lean oil heat exchanger through a second pipeline, and a cooler is arranged on the second pipeline.