Crude oil desalination and dehydration system and process

Abstract

The invention relates to the field of petrochemical engineering, in particular to a crude oil desalination and dehydration system and process, and the crude oil desalination and dehydration system comprises a crude oil conveying device, a water injection mixing device, a demulsifier injection mixing device, an oil-water separation device and a desalination tank. According to the system and the process provided by the invention, a better mixing effect is realized, so that active ingredients are directly separated out after crude oil is dehydrated and desalted and enter a subsequent treatment device, and the rest active ingredients enter the desalting tank for secondary treatment, namely, the treatment load of the desalting tank is reduced, and the desalting tank can work under a relatively small load; safety problems such as tripping caused by ultrahigh electric desalting current are avoided, and safe and stable operation of the device is ensured. Meanwhile, a desalting tank of an existing desalting and dewatering device is omitted, the equipment investment is small, and the device can adapt to the trend of poor quality and heavy quality of crude oil.

Description

Technical Field

[0001] The present invention relates to the field of petrochemical industry, and in particular to a treatment device and process before crude oil refining, and specifically to a crude oil desalting and dehydrating system and process. Background Art

[0002] In the field of petrochemicals, crude oil often contains a certain amount of salt and water after it is extracted from the oil well. If it is not treated, it will cause scaling or blockage of subsequent refining equipment and pipelines, as well as energy waste. In serious cases, it will burn through the heating furnace tubes, block the heat exchanger tubes, and cause equipment corrosion and perforation, and combustible leakage, bringing risks of accidents such as fire and explosion. Therefore, crude oil needs to be desalted and dehydrated before it can enter the device for processing.

[0003] Figure 1 This is the process flow of the existing typical crude oil secondary desalting and dehydrating device. The crude oil is transported by the crude oil pump, and the demulsifier is injected into the crude oil pump inlet pipeline, and the liquid water is injected into the crude oil pump outlet pipeline. After being mixed in the primary mixer, the crude oil enters the primary desalting tank. The crude oil treated in the primary desalting tank is injected with demulsifier and liquid water again, and then mixed in the secondary mixer and enters the secondary desalting tank. After the above two stages of desalting and dehydration, the crude oil enters the subsequent processing device.

[0004] At the same time, in the existing desalting and dehydrating devices, the two-stage desalting tanks mostly adopt the principle of electrical desalting, that is, in order to remove the salt substances suspended in the crude oil, a certain amount of liquid water and demulsifier are injected into the crude oil. The mixture of crude oil, liquid water and demulsifier after full mixing, under the joint action of demulsifier and high-voltage electric field, causes the tiny water droplets to gradually gather into larger water droplets. While settling and separating from the oil with the help of gravity, the salt substances dissolved in the water droplets are also separated and discharged together, thereby achieving the effect of desalting and dehydrating.

[0005] However, in the above process, the effect of electrical desalination depends largely on the mixing effect of crude oil, liquid water and demulsifier, that is, the mixing effect of the two-stage mixer. However, the existing mixers are often simple in structure, and because in the actual production process, the injection amount of demulsifier is very small compared with the mass of crude oil, when the mixture flows through the mixer, the distribution state of the trace amount of demulsifier in the remaining mixed medium will not produce a dispersed effect due to the disordered flow of the mainstream, that is, a good mixing effect cannot be achieved, thereby affecting the subsequent electrical desalination effect.

[0006] Taking the atmospheric and vacuum unit with an annual processing capacity of 8 million tons as an example, the crude oil processed by the unit has the characteristics of high acid value and high salt content. The specific properties are shown in the table below:

[0007] According to the existing crude oil desalting and dehydration equipment, after the crude oil is heated to 130°C after heat exchange, 5 mg / L of demulsifier is first injected to reduce the strength of the oil-water interface film and improve the demulsification effect; then water is injected, and the water injection volume is 5% of the crude oil processing volume. Water is used to dissolve the salt in the crude oil. After two-stage desalting and dehydration, the final salt content of the crude oil is 7.89 mg / L, which is much higher than the 3 mg / L specified in the standard.

[0008] Moreover, as crude oil production enters the middle and late stages, and the deterioration and heaviness of crude oil worldwide are becoming more and more serious, the salt and water content of the produced crude oil continues to increase, and the composition is complex and the emulsification is serious. For example, typical domestic inferior heavy oils include Shengli crude oil, Xinjiang heavy oil, Liaohe heavy oil, etc., as well as Venezuelan extra-heavy heavy oil, etc. The existing crude oil desalting and dehydration processes and equipment can no longer meet the processing and treatment requirements. Many refinery electric desalting devices are seriously emulsified, and a thick emulsion layer accumulates in the electric desalting tank, the oil-water boundary is blurred, and the emulsion layer contains a large amount of highly conductive polar substances, causing the electric desalting device to have unstable current, and even the electric desalting current is too high to cause tripping and other problems. Not only does it reduce the desalting and dehydration pass rate, but it also affects the safe and stable operation of the electric desalting device. Summary of the invention

[0009] In view of the problems raised in the background technology, the purpose of the present invention is to provide a crude oil desalting and dehydration system and process, aiming to improve the dehydration and desalting pass rate of crude oil, and the system and method proposed in the present invention reduce the equipment investment cost, operate stably and have high efficiency.

[0010] To achieve the above object, the present invention adopts the following technical solutions: Firstly, the present invention proposes a crude oil desalting and dehydrating system, comprising a crude oil conveying device, a water injection mixing device, a demulsifier injection mixing device, an oil-water separation device and a desalting tank, wherein the crude oil conveying device is connected to the water injection mixing device, the water injection mixing device is connected to an external water source, and the output port of the water injection mixing device is connected to the demulsifier injection mixing device; the demulsifier injection mixing device is connected to an external demulsifier conveying device, and the output interface of the demulsifier injection mixing device is connected to the oil-water separation device; the crude oil outlet of the oil-water separation device is connected to an external subsequent treatment device, and the sewage outlet of the oil-water separation device is connected to the desalting tank; the desalted crude oil outlet of the desalting tank is connected to an external subsequent treatment device, and the sewage outlet is connected to an external sewage treatment device.

[0011] The water injection mixing device comprises a mixer body, a mixing unit and a guide pipe, the crude oil conveying device is connected to the inlet of the mixer body through a pipeline, one end of the guide pipe passes through the mixer body to connect to an external water source, and the other end is located inside the mixer body, and a plurality of mixing units are sleeved at intervals on the outer edge surface of the guide pipe; the mixing unit has a curved surface mixer, the inner ring of the medium outlet of the curved surface mixer is sleeved with the outer edge surface of the guide pipe, and the outer ring of the medium outlet of the curved surface mixer is connected to the inner edge surface of the inner wall of the mixer body; the outlet of the mixer body serves as the output port of the water injection mixing device, and is connected to the demulsifier injection mixing device.

[0012] The curved surface mixer is a trumpet-shaped structure with a small opening at one end and a large opening at the other end. An outer curved surface flow channel is provided on the outer surface of the curved surface mixer, and an inner curved surface flow channel is provided on the inner surface of the curved surface mixer.

[0013] One end of the curved mixing body is fixedly connected to a mixing unit body, and a through inner hole is arranged in the middle of the end surface of the mixing unit body; the guide tube is inserted into the inner hole, and the outer edge surface of the guide tube is fixedly connected to the inner hole.

[0014] The guide tube is an L-shaped tube as a whole, one end of which is penetrated through the tube wall of the mixer tube body, and the other end is located at the front end of the tube cavity of the mixer tube body.

[0015] The demulsifier injection and mixing device comprises a return pipe, an introduction pipe and a mixer body, wherein the inlet hole of the mixer body is connected to the output port of the water injection and mixing device, and the outlet hole of the mixer body is connected to the oil-water separation device; a throat hole is provided in the middle of the mixer body, the inlet hole of the mixer body is connected to one end of the throat hole through a gradually shrinking hole, and the other end of the throat hole is connected to the outlet hole of the mixer body through a gradually expanding hole; one end of the return pipe is connected to the middle of the throat hole, and the other end is connected to the outlet hole; one end of the introduction pipe is connected to an external demulsifier delivery device, and the other end is connected to the return pipe.

[0016] The oil-water separation device is a cyclone oil-water separator that adopts the centrifugal separation principle.

[0017] The crude oil delivery device is a crude oil pump.

[0018] The present invention also proposes a crude oil desalting and dehydrating process, comprising the following steps: Step S1, crude oil and water are respectively input into a water injection mixing device for mixing, and an oil-water mixture is output; Step S2, the oil-water mixture and the demulsifier are respectively input into a demulsifier mixing device for mixing, and a secondary mixture is output; Step S3, the secondary mixture is input into an oil-water separation device for oil-water separation, and primary desalted crude oil and primary wastewater are output; Step S4, the crude oil after primary desalting is input into an external subsequent treatment device; the primary wastewater is sent to a desalting tank for secondary separation; Step S5, the desalting tank outputs secondary desalting crude oil and secondary sewage; the secondary desalting crude oil is input into a subsequent treatment device, and the secondary sewage is input into an external sewage treatment device.

[0019] In step S1, the injection ratio of crude oil to water is 95:5.

[0020] In step S2, the injection amount of the demulsifier is: 5 ml of demulsifier is injected per liter of the secondary mixture.

[0021] Compared with the prior art, the present invention has the following advantages: 1) The process concept of the present invention is to utilize the mixing effect of the injected liquid water and demulsifier with the crude oil to make the oil-water phase interface clear before oil-water separation, and no longer be in a state of disordered oil-water mixing, which provides sufficient guarantee for the subsequent efficient oil-water separation.

[0022] 2) Compared with the existing desalination and dehydration process, the process of the present invention is more concise and efficient. Since the oil-water separation of the process of the present invention is mainly ensured by the mixing effect of the water injection mixing device and the demulsifier injection mixing device, a desalting tank of the existing desalination and dehydration device can be omitted, thereby reducing the fixed investment of the equipment.

[0023] 3) The system and process of the present invention achieve a better mixing effect, so that the effective components of crude oil can be directly separated into subsequent processing devices after dehydration and desalination, and the remaining components can be sent to the desalter for secondary treatment, which reduces the processing load of the desalter and enables the desalter to work under a smaller load, avoiding safety problems such as tripping caused by excessively high electric desalting current, and ensuring safe and stable operation of the device.

[0024] 4) The system and process of the present invention can adapt to the trend of crude oil deterioration and heaviness. Since the water injection mixing device and the demulsifier injection mixing device in the system can efficiently mix the crude oil with liquid water and demulsifier to achieve a better mixing effect, when the properties of the crude oil change, the liquid water and demulsifier can be increased or adjusted to adapt to the changes in the properties of the crude oil, which means better product adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a typical flow chart of an existing crude oil secondary desalting and dehydration device.

[0026] Figure 2 The figure is a flow chart of the process and device described in the present invention.

[0027] Figure 3 This is a schematic diagram of the structure of the water injection mixing device.

[0028] Figure 4 Schematic diagram of the structure of the mixing unit.

[0029] Figure 5 This is the right side view of the mixing unit.

[0030] Figure 6 This is the left side view of the mixing unit.

[0031] Figure 7 for Figure 6 AA section view.

[0032] Figure 8 for Figure 6 BB cross-sectional view.

[0033] Fig. 9 This is a schematic diagram of the structure of the demulsifier injection mixing device.

[0034] Fig.10 This is a schematic diagram of the working principle of the demulsifier injection mixing device.

[0035] Figure 2-10 In: 1. Crude oil conveying device; 2. Water injection mixing device; 3. Demulsifier injection mixing device; 4. Oil-water separation device; 5. Desalting tank; 11. Crude oil; 12. Liquid water; 13. Demulsifier; 14. Crude oil after primary desalting; 15. Primary sewage; 16. Crude oil after secondary desalting; 17. Secondary sewage, 18. Return medium, 19. Primary mixed medium, 20. Oil-water mixture; 21. mixer tube body, 22. mixing unit, 23. flow guide tube; 201. mixing unit body, 202. inner hole, 221. curved surface mixing body, 222. medium outlet outer ring, 223. medium outlet inner ring, 232. inner curved surface flow channel, 234. outer curved surface flow channel; 30. Mixer body, 301. Throat hole, 302. Inlet hole, 303. Gradually shrinking hole, 304. Gradually expanding hole, 305. Outlet hole, 34. Return pipe, 35. Inlet pipe. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0037] like Figure 2As shown, the present invention first proposes a crude oil desalting and dehydrating system, comprising a crude oil conveying device 1, a water injection mixing device 2, a demulsifier injection mixing device 3, an oil-water separator 4 and a desalting tank 5, wherein the crude oil conveying device 1 is connected to the water injection mixing device 2, the water injection mixing device 2 is connected to an external water source, and the output port of the water injection mixing device 2 is connected to the demulsifier injection mixing device 3; the demulsifier injection mixing device 3 is connected to an external demulsifier conveying device, and the output interface of the demulsifier injection mixing device 3 is connected to the oil-water separator 4; the crude oil outlet of the oil-water separator 4 is connected to an external subsequent treatment device, and the sewage outlet of the oil-water separator 4 is connected to the desalting tank 5; the desalted crude oil outlet of the desalting tank 5 is connected to an external subsequent treatment device, and the sewage outlet is connected to an external sewage treatment device.

[0038] The water injection mixing device 2 is a domestic patent CN202020534712.2 (a low pressure drop and high efficiency pipeline mixer). Figure 3-8 As shown, the water injection mixing device 2 includes a mixer body 21, a mixing unit 22 and a guide pipe 23. The crude oil conveying device is connected to the inlet of the mixer body 21 through a pipeline. One end of the guide pipe 23 passes through the mixer body 21 to connect to an external water source, and the other end is located inside the mixer body 21. A plurality of mixing units 22 are sleeved at intervals on the outer edge surface of the guide pipe 23; the mixing unit 22 has a curved surface mixer 221, and the medium outlet inner ring 223 of the curved surface mixer 221 is sleeved with the outer edge surface of the guide pipe 23, and the medium outlet outer ring 222 of the curved surface mixer 221 is connected to the inner edge surface of the inner wall of the mixer body 21; the outlet of the mixer body 21 serves as the output port of the water injection mixing device 2, and is connected to the demulsifier injection mixing device 3.

[0039] The curved mixer 221 is a trumpet-shaped structure with a small opening at one end and a large opening at the other end. An outer curved flow channel 234 is provided on the outer surface of the curved mixer 221 , and an inner curved flow channel 232 is provided on the inner surface of the curved mixer 221 .

[0040] One end of the curved mixing body 221 is fixedly connected to the mixing unit body 201 , and a through inner hole 202 is provided in the middle of the end surface of the mixing unit body 201 ; the guide tube 23 is inserted into the inner hole 202 , and the outer edge surface of the guide tube 23 is fixedly connected to the inner hole 202 .

[0041] The guide tube 23 is an L-shaped tube as a whole, one end of which is penetrated through the tube wall of the mixer tube body 21 , and the other end is located at the front end of the tube cavity of the mixer tube body 21 .

[0042] The demulsifier injection mixing device is a domestic patent CN216878804U (a mixer using a Venturi structure). Figure 9-10As shown, the demulsifier injection and mixing device 3 includes a return pipe 34, an introduction pipe 35 and a mixer body 30, the inlet hole 302 of the mixer body 30 is connected to the output port of the water injection and mixing device 2, and the outlet hole 305 of the mixer body 30 is connected to the oil-water separation device 4; a throat hole 301 is provided in the middle of the mixer body 30, the inlet hole 302 of the mixer body 30 is connected to one end of the throat hole 301 through a gradually shrinking hole 303, and the other end of the throat hole 301 is connected to the outlet hole 305 of the mixer body 30 through a gradually expanding hole 304; one end of the return pipe 34 is connected to the middle of the throat hole 301, and the other end is connected to the outlet hole 305; one end of the introduction pipe 35 is connected to an external demulsifier conveying device, and the other end is connected to the return pipe 34. The principle of the demulsifier injection and mixing device is to set a return pipe 34 between the throat hole 301 and the outlet hole 305, and use the pressure difference to form a reflux between the throat hole 301 and the outlet hole 305. Then, the introduction pipe 35 is connected to the middle section of the return pipe 34 to mix the demulsifier 13 with the return medium 18 to form a primary mixed medium 19. Since the return medium 18 is relatively small relative to the injected oil-water mixture 20, when the demulsifier 13 is mixed with the return medium 18, the mixing ratio of the two has been greatly improved compared to the direct mixing of the demulsifier 13 and the oil-water mixture 20, so a better mixing effect can be achieved. Then, the mixed primary mixed medium 19 flows back to the middle section of the throat hole 301 through the return pipe 34, and secondary mixing occurs with the injected oil-water mixture 20 in the middle section of the throat hole 301, further improving the mixing effect. Due to the enhanced mixing in the demulsifier injection mixing device 3, the demulsifier 13 is fully utilized, and when the output mixture enters the oil-water separation device 4, the oil-water phase interface is clear, and the conventional oil-water separation device 4 can be used directly for oil-water separation.

[0043] The crude oil conveying device 1, the oil-water separation device 4 and the desalting tank 5 are all prior art. In one embodiment of the present invention, the oil-water separation device 4 is a cyclone oil-water separator using the centrifugal separation principle.

[0044] In one embodiment of the present invention, the crude oil delivery device 1 is a crude oil pump.

[0045] The present invention also proposes a crude oil desalting and dehydrating process, comprising the following steps: Step S1, crude oil and water are respectively input into a water injection mixing device for mixing, and an oil-water mixture is output; Step S2, the oil-water mixture and the demulsifier are respectively input into a demulsifier mixing device for mixing, and a secondary mixture is output; Step S3, the secondary mixture is input into an oil-water separation device for oil-water separation, and primary desalted crude oil and primary wastewater are output; Step S4, the crude oil after primary desalting is input into an external subsequent treatment device; the primary wastewater is sent to a desalting tank for secondary separation; Step S5, the desalting tank outputs secondary desalting crude oil and secondary sewage; the secondary desalting crude oil is input into a subsequent treatment device, and the secondary sewage is input into an external sewage treatment device.

[0046] In step S1, the injection ratio of crude oil to water is 95:5.

[0047] In step S2, the injection amount of the demulsifier is: 5 ml of demulsifier is injected per liter of the secondary mixture.

[0048] The principle of the present invention is as follows Figure 2 As shown: When the crude oil desalting and dehydration system is in working condition, the crude oil 11 first enters the water injection mixing device 2 after being transported by the crude oil conveying device 1. The liquid water 12 injected into the unit is fully mixed with the crude oil 11 under the action of the water injection mixing device 2. To ensure the mixing effect, the equipment scheme adopted is: CN202020534712.2, a low pressure drop and high efficiency pipeline mixer. Then it enters the demulsifier injection mixing device 3, and continues to mix with the injected demulsifier 13 in the device. At the same time, since the injection amount of the demulsifier 13 is very small compared with the crude oil 11, to ensure the mixing effect, the equipment scheme adopted is: CN216878804U, a mixer with a Venturi structure, to ensure the mixing effect of trace fluids. Then, when the crude oil 11 is fully mixed with the liquid water 12 and the demulsifier 13, the oil-water phase boundary is clear due to the effect of the demulsifier 13, and the oil and water are no longer in a disordered mixed state. Therefore, after the mixture enters the oil-water separation device 4, the effective components in the crude oil 11, that is, the primary de-oiled crude oil 14, are separated from the oil-water separation device 4 and can directly enter the external subsequent treatment device. Since the separated primary sewage 15 still contains more effective components, it is sent to the desalting tank 5 for secondary separation, and is further separated under the action of electric desalting and dehydration or other separation schemes. After separation, secondary de-oiled crude oil 16 and secondary sewage 17 are formed. The secondary de-oiled crude oil 16 enters the subsequent treatment device, and the secondary sewage 17 enters the external sewage treatment device.

[0049] Taking the atmospheric and vacuum unit with an annual processing capacity of 8 million tons as an example, the system and process of the present invention are used for treatment, and a water injection volume of 5% and a demulsifier injection volume of 5 mg / L are also used. The system and process of the present invention can make water and crude oil fully contact and fully dissolve the salt in the crude oil; at the same time, the demulsifier is more fully and evenly dispersed, thereby avoiding crude oil emulsification. The salt content of the crude oil after demulsification can reach 2.0 mg / L, which is far lower than the 3 mg / L specified in the standard, which can effectively reduce the corrosion problem of subsequent equipment and save energy consumption.

[0050] Parts of the present invention not described in detail are prior art.

Claims

1. A crude oil desalting and dehydrating system, comprising a crude oil conveying device (1), a water injection mixing device (2), an emulsifier injection mixing device (3), an oil-water separation device (4) and a desalting tank (5), wherein: The crude oil conveying device (1) is connected to a water injection mixing device (2), the water injection mixing device (2) is connected to an external water source, and the output port of the water injection mixing device (2) is connected to an injection and demulsifier mixing device (3); the injection and demulsifier mixing device (3) is connected to an external demulsifier conveying device, and the output interface of the injection and demulsifier mixing device (3) is connected to an oil-water separation device (4); the crude oil outlet of the oil-water separation device (4) is connected to an external subsequent treatment device, and the sewage outlet of the oil-water separation device (4) is connected to a desalting tank (5); the desalting crude oil outlet of the desalting tank (5) is connected to an external subsequent treatment device, and the sewage outlet is connected to an external sewage treatment device.

2. The crude oil desalting and dehydrating system according to claim 1, characterized in that: The water injection mixing device (2) comprises a mixer tube body (21), a mixing unit (22) and a flow guide pipe (23); a crude oil delivery device is connected to the inlet of the mixer tube body (21) through a pipeline; one end of the flow guide pipe (23) passes through the mixer tube body (21) to connect to an external water source, and the other end is located inside the mixer tube body (21); a plurality of mixing units (22) are sleeved at intervals on the outer edge surface of the flow guide pipe (23); the mixing unit (22) has a curved surface mixer (221); an inner ring (223) of a medium outlet of the curved surface mixer (221) is sleeved with the outer edge surface of the flow guide pipe (23); and an outer ring (222) of a medium outlet of the curved surface mixer (221) is connected to the inner edge surface of the inner wall of the mixer tube body (21); the outlet of the mixer tube body (21) serves as an output port of the water injection mixing device (2) and is connected to the demulsifier injection mixing device (3).

3. The crude oil desalting and dehydrating system according to claim 2, characterized in that: The curved surface mixer (221) is a trumpet-shaped structure with a small opening at one end and a large opening at the other end. An outer curved surface circulation channel (234) is provided on the outer surface of the curved surface mixer (221), and an inner curved surface circulation channel (232) is provided on the inner surface of the curved surface mixer (221).

4. The crude oil desalting and dehydrating system according to claim 2, characterized in that: One end of the curved surface mixing body (221) is fixedly connected to a mixing unit body (201), and a through inner hole (202) is provided in the middle of the end surface of the mixing unit body (201); the guide tube (23) is inserted into the inner hole (202), and the outer edge surface of the guide tube (23) is fixedly connected to the inner hole (202).

5. The crude oil desalting and dehydrating system according to claim 4, characterized in that: The guide tube (23) is an L-shaped tube as a whole, one end of which is inserted into the tube wall of the mixer tube body (21), and the other end of which is located at the front end of the tube cavity of the mixer tube body (21).

6. The crude oil desalting and dehydrating system according to claim 1, characterized in that: The demulsifier injection and mixing device (3) comprises a return pipe (34), an introduction pipe (35) and a mixer body (30); the inlet hole (302) of the mixer body (30) is connected to the output port of the water injection and mixing device (2), and the outlet hole (305) of the mixer body (30) is connected to the oil-water separation device (4); a throat hole (301) is provided in the middle of the mixer body (30); the inlet hole (302) of the mixer body (30) is connected to one end of the throat hole (301) through a gradually shrinking hole (303), and the other end of the throat hole (301) is connected to the outlet hole (305) of the mixer body (30) through a gradually expanding hole (304); one end of the return pipe (34) is connected to the middle of the throat hole (301), and the other end is connected to the outlet hole (305); one end of the introduction pipe (35) is connected to an external demulsifier delivery device, and the other end is connected to the return pipe (34).

7. A crude oil desalting and dehydrating process, characterized by: The following steps are involved: Step S1, crude oil and water are respectively input into a water injection mixing device for mixing, and an oil-water mixture is output; Step S2, the oil-water mixture and the demulsifier are respectively input into a demulsifier mixing device for mixing, and a secondary mixture is output; Step S3, the secondary mixture is input into an oil-water separation device for oil-water separation, and primary desalted crude oil and primary wastewater are output; Step S4, the crude oil after primary desalting is input into an external subsequent treatment device; the primary wastewater is sent to a desalting tank for secondary separation; Step S5, the desalting tank outputs secondary desalting crude oil and secondary sewage; the secondary desalting crude oil is input into a subsequent treatment device, and the secondary sewage is input into an external sewage treatment device.

8. The crude oil desalting and dehydrating process according to claim 7, characterized in that: In step S1, the injection ratio of crude oil to water is 95:

5.

9. The crude oil desalting and dehydrating process according to claim 7, characterized in that: In step S2, the injection amount of the demulsifier is: 5 ml of the demulsifier is injected per liter of the secondary mixture.

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