Reverse oil extraction system

Abstract

The utility model relates to the technical field of liquefied petroleum gas alkali washing, and discloses a reverse extraction oil system which comprises a raw material input unit, a first separation unit, a second separation unit, a third separation unit and a reverse extraction oil output unit, the raw material input unit comprises a raw material input pipe; the first separation unit comprises a three-phase separation tank, a liquid output pipe, a gas output pipe and a first delivery pump; the second separation unit comprises a liquid input pipe, a demineralized water input pipe, a washing settling tank, a first conveying pipe and a first alkali liquor discharge pipe; the third separation unit comprises a liquid separation tank, a second conveying pipe and a second alkali liquor discharge pipe; the reverse extraction oil output unit comprises a reverse extraction oil output pipe; according to the reverse extraction oil system provided by the utility model, reverse extraction oil and alkali liquor can be separated for three times through the three-phase separation tank, the washing settling tank and the liquid separation tank, so that the reverse extraction oil and the alkali liquor are separated more thoroughly, and the separation effect is improved.

Description

Technical Field

[0001] This utility model relates to the field of petroleum liquefaction gas alkaline washing technology, and in particular to a reverse extraction oil system. Background Technology

[0002] In the process of removing mercaptans using alkali extraction in oil refineries, the alkali solution after absorbing mercaptans needs to be regenerated and recycled. The disulfides produced during alkali regeneration are difficult to completely separate in the system and are prone to backmixing. Generally, hydrotreated naphtha is used as the back-extraction oil to extract and absorb the disulfides backmixed in the alkali solution, thus ensuring the quality of the alkali solution. Since the alkali solution uses sodium alkali, the hydrotreated naphtha, as the back-extraction oil, is prone to carrying sodium ions when it comes into contact with the alkali solution. Excessive sodium ion content can easily cause corrosion of the furnace tubes when the back-extraction oil is sent to ethylene cracking, affecting the operating cycle of the ethylene furnace.

[0003] Current reverse extraction systems typically use three-phase separators for simple settling to separate the alkali solution from the reverse extraction oil, but the separation effect is not ideal. Utility Model Content

[0004] Aimed at solving at least one of the technical problems existing in the prior art, this utility model provides a reverse extraction oil system that can more thoroughly separate reverse extraction oil and alkali solution, thereby improving the separation effect.

[0005] To achieve the above objectives, this utility model provides a reverse extraction oil system, comprising a raw material input unit, a first separation unit, a second separation unit, a third separation unit, and a reverse extraction oil output unit; the raw material input unit includes a raw material input pipe; the first separation unit includes a three-phase separation tank, the outlet end of the raw material input pipe being connected to the three-phase separation tank; the second separation unit includes a demineralized water input pipe and a water washing settling tank, the demineralized water input pipe being connected to the water washing settling tank, and the water washing settling tank being connected to the three-phase separation tank; the third separation unit includes a liquid separator, the liquid separator being connected to the water washing settling tank; the reverse extraction oil output unit includes a reverse extraction oil output pipe, the reverse extraction oil output pipe being connected to the liquid separator.

[0006] In some embodiments, the first separation unit further includes a liquid output pipe, a gas output pipe, and a first delivery pump. The inlet end of the liquid output pipe is connected to the three-phase separation tank, the first delivery pump is installed on the liquid output pipe, the inlet end of the gas output pipe is connected to the three-phase separation tank, and an exhaust valve is installed on the gas output pipe. The second separation unit further includes a liquid input pipe, a first delivery pipe, and a first alkali discharge pipe. The outlet end of the liquid output pipe is connected to the liquid input pipe, the outlet end of the demineralized water input pipe is connected to the liquid input pipe, the outlet end of the liquid input pipe is connected to the water washing settling tank, the inlet end of the first delivery pipe is connected to the water washing settling tank, and the inlet end of the first alkali discharge pipe is connected to the water washing settling tank. The third separation unit further includes a second delivery pipe and a second alkali discharge pipe. The outlet end of the first delivery pipe is connected to the separator, the inlet end of the second delivery pipe is connected to the separator, the outlet end of the second delivery pipe is connected to the reverse extraction oil output pipe, and the inlet end of the second alkali discharge pipe is connected to the separator.

[0007] In some embodiments, the liquid output pipe is sequentially equipped with a first control valve, a second control valve, a third control valve, and a fourth control valve along the flow direction of the fluid, and the first delivery pump is located between the second control valve and the third control valve.

[0008] In some embodiments, the first separation unit further includes a first bypass pipe, the inlet end of which is connected to the first delivery pipe, the inlet end of which is located between the first control valve and the second control valve, the outlet end of which is connected to the first delivery valve, the outlet end of which is located between the third control valve and the fourth control valve, and a first bypass valve is installed on the first bypass pipe.

[0009] In some embodiments, the liquid inlet pipe is sequentially equipped with a first inlet valve, a static mixer, and a second inlet valve along the flow direction of the fluid, with the first inlet valve located between the inlet end of the demineralized water inlet pipe and the static mixer.

[0010] In some embodiments, the third separation unit further includes a second delivery pump, which is mounted on the second delivery pipe.

[0011] In some embodiments, the reverse extraction oil output unit further includes a filter installed in the reverse extraction oil output pipe.

[0012] In some embodiments, an output valve is installed on the reverse extraction oil output pipe.

[0013] In some embodiments, the reverse extraction oil system further includes a fourth separation unit, which includes a third delivery pipe, an adsorption tank, and a fourth delivery pipe. The inlet end of the third delivery pipe is connected to the second delivery pipe, and the outlet end of the third delivery pipe is connected to the adsorption tank, which contains an adsorbent. The inlet end of the fourth delivery pipe is connected to the adsorption tank, and the outlet end of the fourth delivery pipe is connected to the reverse extraction oil output pipe.

[0014] In some embodiments, the reverse extraction system further includes a sampling unit comprising a sampling tube, a sampling valve, and a sampler. The inlet end of the sampling tube is connected to the second delivery tube, and the sampling valve and the sampler are sequentially installed on the sampling tube along the flow direction of the fluid.

[0015] Compared with the prior art, the reverse extraction oil system provided in this embodiment of the utility model has the following advantages: The raw material containing alkali solution, reverse extraction oil, and tail gas is fed into a three-phase separator through a raw material input pipe, where the alkali solution, reverse extraction oil, and tail gas undergo a first separation. The mixture of alkali solution and reverse extraction oil after the first separation is then transported to a water washing settling tank. Demineralized water is input into the water washing settling tank through a demineralized water input pipe, where the reverse extraction oil undergoes a second separation to separate most of the alkali solution from the oil. The mixture of alkali solution and reverse extraction oil after the second separation is then transported to a separating tank, where the specific gravity of the alkali solution relative to the reverse extraction oil is determined. The basic principle is to perform a third separation on the back-extraction oil to separate the alkali solution from the back-extraction oil. After the three-phase separation process, the back-extraction oil is transported to the back-extraction oil output pipe, which then transports the back-extraction oil to the ethylene cracking furnace. Therefore, the back-extraction oil system provided by this utility model can perform three-phase separation processes on the back-extraction oil and alkali solution through a three-phase separation tank, a water washing settling tank, and a liquid separator, which can more thoroughly separate the back-extraction oil and alkali solution, improve the separation effect, and thus reduce the sodium ion content in the back-extraction oil. This avoids corrosion of the furnace tubes caused by excessive sodium ion content when the back-extraction oil is sent to the ethylene cracking furnace, and helps to ensure the operating cycle of the ethylene furnace. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a reverse extraction oil system provided in an embodiment of the present invention;

[0017] Figure 2 This is a schematic diagram showing the connection between the raw material input unit and the first separation unit provided in this embodiment of the utility model;

[0018] Figure 3 This is a schematic diagram of the structure of the second separation unit provided in this embodiment of the present invention;

[0019] Figure 4This is a schematic diagram showing the connection of the third separation unit, the reverse extraction oil output unit, and the fourth separation unit provided in this embodiment of the utility model;

[0020] Figure 5 This is a schematic diagram showing the connection between the third separation unit and the sampling unit provided in this embodiment of the utility model.

[0021] In the diagram, 1 is the raw material input unit; 11 is the raw material input pipe; and 111 is the feed valve.

[0022] 2. First separation unit; 21. Three-phase separator; 22. Liquid output pipe; 23. Gas output pipe; 24. First transfer pump; 25. First bypass pipe; 221. First control valve; 222. Second control valve; 223. Third control valve; 224. Fourth control valve; 231. Exhaust valve; 251. First bypass valve;

[0023] 3. Second separation unit; 31. Liquid input pipe; 32. Demineralized water input pipe; 33. Water washing settling tank; 34. First conveying pipe; 35. First alkaline solution discharge pipe; 36. Connecting pipe; 37. Second bypass pipe; 311. First input valve; 312. Static mixer; 313. Second input valve; 321. Demineralized water input valve; 341. First conveying valve; 342. Ninth control valve; 351. First alkaline solution discharge valve; 361. First valve; 362. Second valve; 371. Second bypass valve;

[0024] 4. Third separation unit; 41. Separating tank; 42. Second delivery pipe; 43. Second alkali discharge pipe; 44. Second delivery pump; 421. Second delivery valve; 422. Fifth control valve; 423. Sixth control valve; 424. Seventh control valve; 425. Eighth control valve; 431. Second alkali discharge valve;

[0025] 5. Back-extraction oil extraction output unit; 51. Back-extraction oil extraction output pipe; 52. Filter; 511. Output valve;

[0026] 6. Fourth separation unit; 61. Third conveying pipe; 62. Adsorption tank; 63. Fourth conveying pipe; 611. Third conveying valve; 631. Fourth conveying valve;

[0027] 7. Sampling unit; 71. Sampling tube; 72. Sampling valve; 73. Sampler. Detailed Implementation

[0028] The specific embodiments of this utility model will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this utility model, but are not intended to limit its scope.

[0029] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0030] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0031] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0032] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0033] like Figures 1-5 As shown, a preferred embodiment of the present invention provides a reverse extraction oil system, comprising a raw material input unit 1, a first separation unit 2, a second separation unit 3, a third separation unit 4, and a reverse extraction oil output unit 5.

[0034] The raw material input unit 1 includes a raw material input pipe 11; the first separation unit 2 includes a three-phase separation tank 21, and the outlet end of the raw material input pipe 11 is connected to the three-phase separation tank 21; the second separation unit 3 includes a demineralized water input pipe 32 and a water washing settling tank 33, and the demineralized water input pipe 32 and the water washing settling tank 33 are connected, and the water washing settling tank 33 is connected to the three-phase separation tank 21; the third separation unit includes a liquid separator 41, and the liquid separator 41 is connected to the water washing settling tank 33; the back-extraction oil output unit 5 includes a back-extraction oil output pipe 51, and the back-extraction oil output pipe 51 is connected to the liquid separator 41.

[0035] Based on this technical solution, the raw material containing alkali solution, back-extraction oil, and tail gas is fed into the three-phase separator 21 through the raw material input pipe 11. The three-phase separator 21 performs the first separation of alkali solution, back-extraction oil, and tail gas. After the first separation, the mixture of alkali solution and back-extraction oil is transported to the washing and settling tank 33. Demineralized water is input into the washing and settling tank 33 through the demineralized water input pipe 32. In the washing and settling tank 33, the back-extraction oil undergoes a second separation to separate most of the alkali solution from the back-extraction oil. After the second separation, the mixture of alkali solution and back-extraction oil is transported to the separating tank 41. In the separating tank 41, the principle that the alkali solution has a higher specific gravity than the back-extraction oil is used to separate the back-extraction oil. The extracted oil undergoes a third separation to separate the alkali solution from the back-extracted oil. After the three separation processes, the back-extracted oil is transported to the back-extracted oil output pipe 51, which then transports the back-extracted oil to the ethylene cracking furnace. Therefore, the back-extracted oil system provided by this utility model can perform three separation processes on the back-extracted oil and alkali solution through a three-phase separation tank, a water washing settling tank, and a liquid separator, which can more thoroughly separate the back-extracted oil and alkali solution, improve the separation effect, and thus reduce the sodium ion content in the back-extracted oil. This prevents corrosion of the furnace tubes due to excessive sodium ion content when the back-extracted oil is sent to the ethylene cracking furnace, and helps to ensure the operating cycle of the ethylene furnace.

[0036] Specifically, the first separation unit also includes a liquid output pipe 22, a gas output pipe 23 and a first delivery pump 24. The inlet end of the liquid output pipe 22 is connected to the three-phase separation tank 21, the first delivery pump 24 is installed on the liquid output pipe 22, and the inlet end of the gas output pipe 23 is connected to the three-phase separation tank 21.

[0037] The second separation unit 3 also includes a liquid input pipe 31, a first conveying pipe 34, and a first alkaline solution discharge pipe 35; the outlet end of the liquid output pipe 22 is connected to the liquid input pipe 31, the outlet end of the demineralized water input pipe 32 is connected to the liquid input pipe 31, and the outlet end of the liquid input pipe 31 is connected to the water washing settling tank 33. That is, the three-phase separation tank 21 is connected to the water washing settling tank 33 through the liquid output pipe 22 and the liquid input pipe 31, and the demineralized water input pipe 32 is connected to the water washing settling tank 33 through the liquid input pipe 31; the inlet end of the first conveying pipe 34 is connected to the water washing settling tank 33, and the inlet end of the first alkaline solution discharge pipe 35 is connected to the water washing settling tank 33.

[0038] The third separation unit 4 also includes a second conveying pipe 42 and a second alkali discharge pipe 43. The outlet end of the first conveying pipe 34 is connected to the separator 41, that is, the water washing settling tank 33 is connected to the separator 41 through the first conveying pipe 34. The inlet end of the second conveying pipe 42 is connected to the separator 41, and the outlet end of the second conveying pipe 42 is connected to the reverse extraction oil output pipe 51, that is, the separator 41 is connected to the reverse extraction oil output pipe 51 through the second conveying pipe 42. The inlet end of the second alkali discharge pipe 43 is connected to the separator 41.

[0039] Specifically, the working process of the reverse extraction oil system provided by this utility model is as follows: the raw material containing alkali solution, reverse extraction oil, and tail gas is sent into the three-phase separation tank 21 through the raw material input pipe 11, and the alkali solution, reverse extraction oil, and tail gas are separated for the first time through the three-phase separation tank 21; the mixture of alkali solution and reverse extraction oil is transported to the first conveying pipe 34 through the liquid output pipe 22, and the demineralized water input pipe 32 inputs demineralized water into the first conveying pipe 34, and the first conveying pipe 34 sends the mixture of alkali solution, reverse extraction oil, and demineralized water into the water washing settling tank 33; in the water washing settling tank 33... The back-extracted oil undergoes a second separation to separate most of the alkali solution from the back-extracted oil and discharge it through the first alkali solution discharge pipe 35; the first conveying pipe 34 conveys the back-extracted oil to the separating tank 41, where the back-extracted oil undergoes a third separation based on the principle that the alkali solution has a higher specific gravity than the back-extracted oil, to separate the alkali solution from the back-extracted oil and discharge it through the second alkali solution discharge pipe 43; the second conveying pipe 42 conveys the back-extracted oil to the back-extracted oil output pipe 51, and the back-extracted oil output pipe 51 conveys the back-extracted oil to the ethylene cracking furnace.

[0040] It should be noted that in this utility model Figures 1-5 In the diagram, the arrow indicates the direction of fluid flow within the pipe, and the end where the arrow is located is the outlet end of the pipe. The other end of the pipe opposite the outlet end is the inlet end of the pipe.

[0041] A feed valve 111 is installed on the raw material input pipe 11.

[0042] An exhaust valve 231 is installed on the gas output pipe 23.

[0043] The liquid output pipe 22 is sequentially equipped with a first control valve 221, a second control valve 222, a third control valve 223 and a fourth control valve 224 along the flow direction of the fluid, and the first delivery pump 24 is located between the second control valve 222 and the third control valve 223.

[0044] The first separation unit 2 also includes a first bypass pipe 25. The inlet end of the first bypass pipe 25 is connected to the first delivery pipe 34 and is located between the first control valve 221 and the second control valve 222. The outlet end of the first bypass pipe 25 is connected to the first delivery pipe 34 and is located between the third control valve 223 and the fourth control valve 224. A first bypass valve 251 is installed on the first bypass pipe 25. When the first delivery pump 24 malfunctions or requires maintenance, the first delivery pump 24 can be isolated from the liquid delivery circuit of the liquid delivery pipe by closing the second control valve 222 and the third control valve 223, which facilitates the maintenance of the first delivery pump 24. At the same time, the first bypass valve 251 is opened to send the mixture of alkali, back-extraction oil and demineralized water into the water washing settling tank 33 through the first bypass pipe 25 and the liquid delivery pipe. The back-extraction oil system has high safety redundancy.

[0045] A demineralized water inlet valve 321 is installed on the demineralized water inlet pipe 32.

[0046] A first input valve 311, a static mixer 312, and a second input valve 313 are sequentially installed on the liquid input pipe 31 along the fluid flow direction. The first input valve 311 is located between the inlet end of the demineralized water input pipe 32 and the static mixer 312. The static mixer 312 can mix the alkali solution, the back-extraction oil mixture, and the demineralized water in the liquid input pipe 31, so that the water washing settling tank 33 can better separate the alkali solution from the back-extraction oil and discharge the alkali solution through the first alkali solution discharge pipe 35. The static mixer 312 can mix the alkali solution, the back-extraction oil mixture, and the demineralized water without additional electricity or power, and has the advantages of high efficiency, energy saving, and environmental protection.

[0047] A first alkali discharge valve 351 is installed on the first alkali discharge pipe 35.

[0048] A first delivery valve 341 is installed on the first delivery pipe 34.

[0049] There are multiple water washing settling tanks 33, which are connected in series. By using multiple water washing settling tanks 33, the back-extracted oil and alkali solution can be washed and settled multiple times to separate more alkali solution from the back-extracted oil.

[0050] Specifically, two adjacent water washing settling tanks 33 are connected by a connecting pipe 36, which is equipped with a first valve 361 and a second valve 362.

[0051] A second delivery valve 421 is installed on the second delivery pipe 42.

[0052] A second alkali discharge valve 431 is installed on the second alkali discharge pipe 43.

[0053] The second separation unit 3 also includes a second bypass pipe 37. The inlet end of the second bypass pipe 37 is connected to the liquid input pipe 31. The outlet end of the demineralized water input pipe 32 is located between the inlet end of the second bypass pipe 37 and the water washing settling tank 33. The outlet end of the second bypass pipe 37 is connected to the first delivery pipe 34. A ninth control valve 342 is installed on the first delivery pipe 34. The outlet end of the second bypass pipe 37 is located between the first delivery valve 341 and the ninth control valve 342. A second bypass valve 371 is installed on the second bypass pipe 37. When the water washing settling tank 33 malfunctions or requires maintenance, the first input valve 311 and the first delivery valve 341 can be closed to isolate the water washing settling tank 33 from the flow circuit of the reverse extraction oil system, facilitating the maintenance of the water washing settling tank 33. At the same time, the second bypass valve 371 is opened to send the reverse extraction oil into the separator 41 for separation through the second bypass pipe 37 and the second delivery pipe 42.

[0054] The third separation unit 4 also includes a second delivery pump 44, which is mounted on the second delivery pipe 42.

[0055] The back-extraction oil output unit 5 also includes a filter 52, which is installed in the back-extraction oil output pipe 51. The filter 52 is used to filter solid particles in the back-extraction oil.

[0056] An output valve 511 is installed on the reverse extraction oil output pipe 51.

[0057] The reverse extraction oil system also includes a fourth separation unit 6, which comprises a third delivery pipe 61, an adsorption tank 62, and a fourth delivery pipe 63. The inlet end of the third delivery pipe 61 is connected to the second delivery pipe 42, and the outlet end of the third delivery pipe 61 is connected to the adsorption tank 62, which contains adsorbent. The inlet end of the fourth delivery pipe 63 is connected to the adsorption tank 62, and the outlet end of the fourth delivery pipe 63 is connected to the reverse extraction oil output pipe 51. The adsorbent in the adsorption tank 62 can further adsorb trace amounts of sodium ions in the reverse extraction oil, thereby further reducing the sodium ion content in the reverse extraction oil.

[0058] A third delivery valve 611 is installed on the third delivery pipe 61.

[0059] A fourth delivery valve 631 is installed on the fourth delivery pipe 63.

[0060] The back-extraction oil extraction system also includes a sampling unit 7, which comprises a sampling pipe 71, a sampling valve 72, and a sampler 73. The inlet end of the sampling pipe 71 is connected to the second delivery pipe 42. The sampler 73 is installed on the sampling pipe 71, and the sampling valve 72 is installed on the sampling pipe 71 and located between the inlet end of the sampling pipe 71 and the sampler 73. Using the sampling unit 7, the back-extraction oil that has undergone three separations can be sampled and analyzed to ensure that the sodium ion content of the back-extraction oil output unit 5 meets the requirements.

[0061] The second delivery pipe 42 is equipped with a fifth control valve 422, a sixth control valve 423, a seventh control valve 424, and an eighth control valve 425 sequentially along the fluid flow direction. The second delivery valve 421 is located between the fifth control valve 422 and the separator 41. The second delivery pump 44 is located between the fifth control valve 422 and the sixth control valve 423. The inlet end of the sampling pipe 71 is located between the fifth control valve 422 and the sixth control valve 423. The inlet end of the third delivery pipe 61 is located between the seventh control valve 424 and the eighth control valve 425.

[0062] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present utility model, and these improvements and substitutions should also be considered within the protection scope of the present utility model.

Claims

1. A system for counter-current oil extraction, characterized in that The application relates to a device for separating and outputting reverse extraction oil, which comprises the following parts: a raw material input unit (1) comprising a raw material input pipe (11); a first separation unit (2) comprising a three-phase separation tank (21), wherein an outlet end of the raw material input pipe (11) is connected with the three-phase separation tank (21); a second separation unit (3) comprising a desalted water input pipe (32) and a water washing sedimentation tank (33), wherein the desalted water input pipe (32) is connected with the water washing sedimentation tank (33), and the water washing sedimentation tank (33) is connected with the three-phase separation tank (21); a third separation unit (4) comprising a liquid separation tank (41), wherein the liquid separation tank (41) is connected with the water washing sedimentation tank (33); a reverse extraction oil output unit (5) comprising a reverse extraction oil output pipe (51), wherein the reverse extraction oil output pipe (51) is connected with the liquid separation tank (41).

2. The oil back-extraction system of claim 1, wherein The first separation unit further comprises a liquid output pipe (22), a gas output pipe (23) and a first conveying pump (24), wherein an inlet end of the liquid output pipe (22) is connected with the three-phase separation tank (21), the first conveying pump (24) is arranged on the liquid output pipe (22), an inlet end of the gas output pipe (23) is connected with the three-phase separation tank (21), and an exhaust valve (231) is arranged on the gas output pipe (23); the second separation unit (3) further comprises a liquid input pipe (31), a first conveying pipe (34) and a first lye discharge pipe (35), wherein an outlet end of the liquid output pipe (22) is connected with the liquid input pipe (31), an outlet end of the desalted water input pipe (32) is connected with the liquid input pipe (31), an outlet end of the liquid input pipe (31) is connected with the water washing sedimentation tank (33), an inlet end of the first conveying pipe (34) is connected with the water washing sedimentation tank (33), and an inlet end of the first lye discharge pipe (35) is connected with the water washing sedimentation tank (33); the third separation unit (4) further comprises a second conveying pipe (42) and a second lye discharge pipe (43), wherein an outlet end of the first conveying pipe (34) is connected with the liquid separation tank (41), an inlet end of the second conveying pipe (42) is connected with the liquid separation tank (41), an outlet end of the second conveying pipe (42) is connected with the reverse extraction oil output pipe (51), and an inlet end of the second lye discharge pipe (43) is connected with the liquid separation tank (41).

3. The oil back-extraction system of claim 2, wherein The liquid output pipe (22) is sequentially provided with a first control valve (221), a second control valve (222), a third control valve (223) and a fourth control valve (224) along the flow direction of fluid, and the first conveying pump (24) is arranged between the second control valve (222) and the third control valve (223).

4. The oil back-extraction system of claim 3, wherein The first separation unit (2) further comprises a first bypass pipe (25), an inlet end of the first bypass pipe (25) is communicated with the first conveying pipe (34), the inlet end of the first bypass pipe (25) is located between the first control valve (221) and the second control valve (222), an outlet end of the first bypass pipe (25) is communicated with the first conveying pipe (34), the outlet end of the first bypass pipe (25) is located between the third control valve (223) and the fourth control valve (224), and the first bypass pipe (25) is provided with a first bypass valve (251).

5. The back-extraction oil system of claim 2, wherein The liquid input pipe (31) is sequentially provided with a first input valve (311), a static mixer (312) and a second input valve (313) along the flow direction of fluid, and the first input valve (311) is located between the inlet end of the desalted water input pipe (32) and the static mixer (312).

6. The oil back-extraction system of claim 2, wherein The third separation unit (4) further comprises a second conveying pump (44), and the second conveying pump (44) is installed on the second conveying pipe (42).

7. The oil back-extraction system of claim 1, wherein The back-extracted oil output unit (5) further comprises a filter (52), and the filter (52) is installed on the back-extracted oil output pipe (51).

8. The oil back-extraction system of claim 1, wherein The back-extracted oil output pipe (51) is provided with an output valve (511).

9. The oil back-extraction system according to any one of claims 2-6, characterized in that, The fourth separation unit (6) comprises a third conveying pipe (61), an adsorption tank (62) and a fourth conveying pipe (63), an inlet end of the third conveying pipe (61) is communicated with the second conveying pipe (42), an outlet end of the third conveying pipe (61) is communicated with the adsorption tank (62), the adsorption tank (62) is provided with an adsorbent, an inlet end of the fourth conveying pipe (63) is communicated with the adsorption tank (62), and an outlet end of the fourth conveying pipe (63) is communicated with the back-extracted oil output pipe (51).

10. The oil back-extraction system of claim 9, wherein, The sampling unit (7) comprises a sampling pipe (71), a sampling valve (72) and a sampler (73), an inlet end of the sampling pipe (71) is communicated with the second conveying pipe (42), and the sampling pipe (71) is sequentially provided with the sampling valve (72) and the sampler (73) along the flow direction of fluid.

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