A high-efficiency dissolved air flotation device for oilfield produced water

Abstract

The utility model discloses a kind of high-efficiency dissolved air flotation devices for oilfield produced water, including dissolved air flotation tank and the placing base of being arranged at the bottom end of dissolved air flotation tank, the dissolved air flotation tank is fixedly connected with placing base by welding, the right side of the inside center of dissolved air flotation tank is provided with dissolved air water release chamber, the left side of the inside center of dissolved air flotation tank is provided with water purification chamber, the right end of water purification chamber is provided with scum chamber, by adding novel water outlet filtration purification device in water outlet, water quality precision is improved by four-stage progressive filtration, it is intercepted large block impurity by stainless steel wire mesh filter screen, modified fiber ball filter screen removes oil, activated carbon filter screen adsorbs pollutant and peculiar smell, precision folding membrane filter screen retains small particle and microorganism, so that water quality meets standard and satisfies reinjection, broaden resource approach, device uses oil stain-resistant, corrosion-resistant material, and grading design can be flexibly adjusted, enhance equipment adaptability and stability, ensure long-term operation.

Description

Technical Field

[0001] The utility model belongs to the technical field related to dissolved air flotation machines, and particularly relates to an efficient dissolved air flotation device for oilfield produced water. Background Technique

[0002] During the oilfield exploitation process, a large amount of produced water is generated. The composition of this kind of water body is complex, containing high concentrations of petroleum substances, suspended particles, colloidal impurities and various organic pollutants. If directly discharged or reused, it will cause serious pollution to the environment, and at the same time, it will also affect the safety and economy of subsequent oilfield exploitation operations. Therefore, efficient purification treatment of oilfield produced water is an indispensable key link in oilfield production. At present, the dissolved air flotation technology is widely used in the treatment of oilfield produced water because it can effectively remove suspended particles and oil substances in the produced water. However, in actual operation, the traditional dissolved air flotation device has the problem of insufficient accuracy of the effluent quality and difficulty in adapting to diverse requirements. Although the traditional dissolved air flotation device can remove most suspended particles and oil through the air flotation effect, there are still trace amounts of oil, fine particles and colloidal impurities remaining in the treated water. If these residual impurities are not further treated, the effluent quality cannot meet the discharge standard, and it is even more difficult to meet the high-standard reuse requirements such as oilfield reinjection, which restricts the resource utilization of the produced water. In addition, the single air flotation treatment link has limited effects on removing organic pollutants and odors, affecting the sensory quality and safety of the effluent;

[0003] On the other hand, the filtration and purification device has poor adaptability and insufficient operation stability. The filter mesh materials of some filtration equipment supporting the dissolved air flotation device have weak anti-oil pollution and anti-corrosion properties, and are prone to aging and damage in the harsh environment of oilfield produced water, resulting in a rapid decline in the filtration effect. At the same time, traditional filtration devices mostly adopt an integrated structure or a fixed filter mesh design, and it is difficult to flexibly adjust the filtration levels according to the fluctuations in the quality of the produced water. When the water quality deteriorates, problems such as excessive filter mesh load and frequent blockage are likely to occur, seriously affecting the continuous and stable operation of the filtration system. Content of the Utility Model

[0004] The purpose of the utility model is to provide an efficient dissolved air flotation device for oilfield produced water, so as to solve the problems in the above background technique that the effluent accuracy of the traditional dissolved air flotation device is insufficient, after removing most suspended particles and oil, there are still trace amounts of oil, fine particles and colloidal impurities remaining, which do not meet the standards without treatment, are difficult to meet the requirements such as oilfield reinjection, restrict the resource utilization, and the single air flotation has limited effects on removing organic pollutants and odors, affecting the sensory and safety of the effluent.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a high-efficiency dissolved air flotation device for oilfield produced water, comprising a dissolved air flotation tank and a mounting base disposed at the bottom of the dissolved air flotation tank. The dissolved air flotation tank and the mounting base are fixedly connected by welding. A dissolved air water release chamber is disposed on the right side of the center of the dissolved air flotation tank, a clean water chamber is disposed on the left side of the center of the dissolved air flotation tank, and a scum chamber is disposed at the right end of the clean water chamber. The scum chamber and the clean water chamber do not interfere with each other. A scum scraper is disposed in the middle section of the top of the dissolved air flotation tank. A water outlet is disposed on the upper side of the center of the left end of the dissolved air flotation tank. The water outlet is connected to the interior of the clean water chamber, and a water filtration and purification device is connected to the left end of the water outlet.

[0006] Preferably, the effluent filtration and purification device includes a final discharge pipe, an effluent connection pipe, a cover handle, a sealing end cap, and a cuboid filtration and purification box. The cuboid filtration and purification box is welded and fixed to the outer wall of the left end of the dissolved air flotation tank, and the top of the cuboid filtration and purification box is open. The cuboid filtration and purification box is located below the effluent outlet. The left end of the effluent outlet is connected and fixed to the effluent connection pipe by a flange and screws. A sealing end cap is provided inside the opening at the top of the cuboid filtration and purification box. A cover handle is provided at the center of the top of the sealing end cap. The final discharge pipe is provided at the rear end of the cuboid filtration and purification box near the lower right corner, and the final discharge pipe communicates with the interior of the cuboid filtration and purification box.

[0007] Preferably, the left half of the water outlet connecting pipe is bent vertically downwards and inserted vertically into the left side of the center of the cuboid filter purification box. The bottom end of the left half of the water outlet connecting pipe is close to the inner wall of the bottom of the cuboid filter purification box. A sleeve hole is provided on the left side of the center of the sealing end cap, and the sealing end cap is sleeved on the outside of the vertical section of the water outlet connecting pipe through the sleeve hole. The sealing end cap can be moved up and down by the opening handle.

[0008] Preferably, the effluent filtration and purification device further includes a detachable filter screen. Multiple sets of U-shaped fixing sleeves are provided at the center of the inner walls of the front and rear ends of the cuboid filtration and purification box and on its left and right sides. The multiple sets of U-shaped fixing sleeves are located in the area between the vertical section of the effluent connecting pipe and the final discharge pipe, and a detachable filter screen is inserted into each set of U-shaped fixing sleeves. After the sealing end cap is closed into the opening at the top of the cuboid filtration and purification box, the bottom end of the sealing end cap is tightly attached to the top of the multiple sets of U-shaped fixing sleeves. The multiple detachable filter screens are stainless steel wire mesh filter screens, modified fiber ball filter screens, activated carbon filter screens, and precision pleated membrane filter screens.

[0009] Preferably, a scum outlet is provided at the front end of the dissolved air flotation tank near the upper left corner. The scum outlet is located below the center of the front end of the scum chamber and is connected to the interior of the scum chamber. When the scraper is running, it can use the scraper plate to send the scum floating on the water surface inside the dissolved air flotation tank into the scum chamber.

[0010] Preferably, an inclined guide plate is connected between the center of the rear inner wall of the scum chamber and the bottom of the front inner wall, so that the scum inside the scum chamber can be guided into the scum discharge outlet and discharged through the inclined guide plate.

[0011] Preferably, an electrical control box is fixed on the left side of the center of the rear outer wall of the dissolved air flotation tank, a delivery pump is installed on the right side of the electrical control box, a dissolved air tank is installed on the right side of the delivery pump, and a dissolved air water release device is installed at the bottom of the dissolved air water release chamber.

[0012] Preferably, the inlet of the delivery pump is connected to an external oilfield produced water supply pipeline. The delivery pump can directly deliver the oilfield produced water into the dissolved air tank through the delivery pipe. The dissolved air tank can deliver the dissolved air water to the dissolved air water release device through the delivery pipe. The dissolved air water release device fully releases the dissolved air water into the dissolved air water release chamber, and the dissolved air water release chamber is connected to the internal area of ​​the middle section of the dissolved air flotation tank.

[0013] Preferably, multiple sludge discharge outlets are provided on the lower side of the center of the front outer wall of the dissolved air flotation tank. The multiple sludge discharge outlets are all close to the bottom of the dissolved air flotation tank. The multiple sludge discharge outlets are respectively connected to the middle section area inside the dissolved air flotation tank, the clean water chamber and the dissolved air water release chamber. The clean water chamber is also connected to a circulation pipe head near the bottom rear end, and the circulation pipe head is connected to the inlet of the delivery pump through a delivery pipe.

[0014] Compared with the prior art, this utility model provides a high-efficiency dissolved air flotation device for oilfield produced water, which has the following beneficial effects:

[0015] This invention adds a novel effluent filtration and purification device to the outlet of the purified water discharge of the high-efficiency dissolved air flotation device. This device can improve the accuracy of the effluent water quality and meet diverse needs. Its stainless steel wire mesh filter first intercepts large suspended impurities to prevent subsequent filter clogging. The modified fiber ball filter efficiently removes emulsified and dispersed oils, significantly reducing the oil content in the water. The activated carbon filter deeply adsorbs trace amounts of oil, organic pollutants, and odors, improving the sensory quality of the water. The precision pleated membrane filter finally traps extremely fine particles and microorganisms. This four-stage filtration system forms a progressive purification system, ensuring that the treated water not only meets discharge standards but also satisfies the reuse requirements for oilfield reinjection, thus broadening the resource utilization pathways of produced water. Furthermore, this effluent filtration and purification device can enhance the adaptability and stability of high-efficiency dissolved air flotation equipment. Targeting the complex composition and high oil content of oilfield produced water, each filter is made of oil-resistant and corrosion-resistant materials, capable of withstanding harsh water quality environments for a long time and reducing filter failures caused by corrosion and aging. At the same time, the staged filtration design allows for flexible adjustment of the filter combination according to water quality fluctuations, avoiding excessive load on a single filter and ensuring long-term stable operation of the filtration system.

[0016] Furthermore, the detachable filter screen of the water filtration and purification device is installed through a U-shaped fixing sleeve. With the opening handle of the sealed end cap, the staff can quickly disassemble and clean or replace the filter screen without complicated tools, which greatly shortens the maintenance time. Compared with the integrated filtration structure, this design reduces the downtime for equipment maintenance and lowers labor costs. In addition, the staged filtration makes the filter screen wear more even, and can be replaced according to the actual degree of pollution of each filter screen, avoiding the material waste caused by replacing the whole screen and further saving operating costs. Attached Figure Description

[0017] Figure 1 This is a front-view three-dimensional structural diagram of a high-efficiency dissolved air flotation device for oilfield produced water according to the present invention.

[0018] Figure 2 This is a rear-view three-dimensional structural diagram of a high-efficiency dissolved air flotation device for oilfield produced water according to the present invention.

[0019] Figure 3 This is a top view schematic diagram of a high-efficiency dissolved air flotation device for oilfield produced water according to the present invention.

[0020] Figure 4 This is a schematic diagram of the external three-dimensional structure of the water filtration and purification device of this utility model.

[0021] Figure 5 This is a cross-sectional perspective view of the water filtration and purification device of this utility model.

[0022] In the diagram: 1. Dissolved air flotation tank; 2. Base; 3. Sludge outlet; 4. Scum outlet; 5. Water filtration and purification device; 6. Water outlet; 7. Clean water chamber; 8. Scum chamber; 9. Scum scraper; 10. Electrical control box; 11. Transfer pump; 12. Dissolved air tank; 13. Dissolved air water release chamber; 14. Dissolved air water release device; 15. Final discharge pipe; 16. Water outlet connection pipe; 17. Opening handle; 18. Sealed end cap; 19. Cuboid filtration and purification box; 20. Removable filter screen. Detailed Implementation

[0023] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0024] This utility model provides, for example Figure 1-5The illustrated high-efficiency dissolved air flotation (DAF) device for oilfield produced water includes a DAF tank 1 and a mounting base 2 located at the bottom of the DAF tank 1. The DAF tank 1 and the mounting base 2 are fixedly connected by welding. This welding method ensures a firm connection, preventing the DAF tank 1 from shifting due to vibration or other factors during operation, and providing a stable support foundation for the entire device. A dissolved air water release chamber 13 is located on the right side of the center inside the DAF tank 1. This location facilitates the release of dissolved air water into the oilfield water entering the middle section of the tank. The extracted water is rapidly mixed to improve the contact efficiency between air bubbles and contaminants. A clean water chamber 7 is located on the left side of the center of the dissolved air flotation tank 1. Its location on the left side allows it to form a reasonable water flow path with the dissolved air water release chamber 13 on the right, enabling the purified water to flow naturally to the outlet 6 on the left. A scum chamber 8 is located at the right end of the clean water chamber 7, and the scum chamber 8 and the clean water chamber 7 are independent of each other. This layout effectively prevents scum from entering the clean water chamber 7 and contaminating the purified water, ensuring the quality of the purified water. A scum scraper 9 is located at the top center of the dissolved air flotation tank 1, directly opposite... The surface area where scum accumulates facilitates efficient scraping of the scum into the scum chamber 8 by the scum scraper 9. An outlet 6 is located on the upper side of the center of the left end of the dissolved air flotation tank 1, communicating with the interior of the clean water chamber 7. This location on the upper left side of the clean water chamber 7 conforms to the characteristic of water flowing downhill, allowing the clean water in the clean water chamber 7 to be smoothly discharged through the outlet 6. A scum discharge outlet 4 is located near the upper left corner of the front end of the dissolved air flotation tank 1, below the center of the front end of the scum chamber 8, and communicating with the interior of the scum chamber 8. This location... The design facilitates the discharge of scum from the scum chamber 8 under its own gravity. When the scraper 9 is running, it can use the scraper plate to send the scum floating on the water surface inside the dissolved air flotation tank 1 into the scum chamber 8, ensuring that the scum can be collected and discharged in a concentrated manner. An inclined guide plate is connected between the center of the rear inner wall and the bottom of the front inner wall of the scum chamber 8. The inclined angle design can use gravity to guide the flow of scum. The scum inside the scum chamber 8 can be guided into the scum discharge outlet 4 through the inclined guide plate and discharged, improving the smoothness of scum discharge and preventing scum from accumulating inside the scum chamber 8.

[0025] like Figure 1 , Figure 2 and Figure 3As shown, an electrical control box 10 is fixed on the left side of the center of the rear outer wall of the dissolved air flotation tank 1, facilitating operator control and operation of the device. A delivery pump 11 is located to the right of the control box 10, and a dissolved air tank 12 is located to the right of the delivery pump 11. These three are arranged in a straight line, shortening the length of connecting pipes between components and reducing energy loss during liquid transport. A dissolved air water release device 14 is located at the bottom of the dissolved air water release chamber 13, ensuring that the released bubbles are evenly distributed in the water, enhancing the contact effect between the bubbles and contaminants. The inlet of the delivery pump 11 is connected to an external oilfield produced water supply pipeline, allowing direct extraction of external oilfield produced water. The delivery pump 11 can directly transport the oilfield produced water into the dissolved air tank 12 through a delivery pipe, ensuring smooth entry of the produced water into the dissolved air stage. The dissolved air tank 12 can transport the dissolved air water to the dissolved air water release device 14 through a delivery pipe, achieving precise delivery of the dissolved air water. The dissolved air water release device 14 fully releases the dissolved air water. The dissolved air water is released into the dissolved air water release chamber 13, which is connected to the middle section of the dissolved air flotation tank 1. This allows the dissolved air water to quickly diffuse into the extracted water in the middle section of the tank, improving the flotation efficiency. Multiple sludge discharge outlets 3 are located on the lower side of the center of the outer wall at the front end of the dissolved air flotation tank 1. These outlets are close to the bottom of the tank. Since sludge has a high density and tends to settle at the bottom of the tank, this location facilitates the complete discharge of the deposited sludge. The multiple sludge discharge outlets 3 are connected to the middle section of the dissolved air flotation tank 1, the clean water chamber 7, and the dissolved air water release chamber 13, respectively. This allows for the targeted discharge of sludge from different areas, ensuring the cleanliness of each area. The clean water chamber 7 is also connected to a circulation pipe head near the bottom rear end. This circulation pipe head is connected to the inlet of the transfer pump 11 via a delivery pipe. This location allows some of the incompletely purified water in the clean water chamber 7 to be transported back to the transfer pump 11 for circulation treatment, improving the wastewater treatment effect and water resource utilization rate.

[0026] like Figure 1 , Figure 2 and Figure 3As shown, this high-efficiency dissolved air flotation (DAF) device for oilfield produced water purifies the water through the synergistic effects of dissolved air, air release, flotation separation, and solid-liquid separation. Specifically, firstly, external oilfield produced water enters the delivery pump 11 through a pipeline. After being pressurized by the delivery pump 11, it is sent to the dissolved air tank 12. Inside the dissolved air tank 12, air is fully dissolved in the water under pressure, forming high-pressure dissolved air water. Subsequently, the dissolved air water is transported through a delivery pipe to the dissolved air water release device 14 inside the dissolved air flotation tank 1. When the dissolved air water is sprayed out from the release device into the dissolved air water release chamber 13, the pressure drops sharply to atmospheric pressure, and the dissolved air is rapidly released in the form of a large number of tiny bubbles. These tiny bubbles are fully mixed with the produced water in the dissolved air water release chamber 13 and the middle section of the tank. Due to their large surface area and adsorption capacity, the bubbles quickly adsorb suspended particles, emulsified oil, and other contaminants in the water. The pollutants form a gas-solid complex with a density less than water. Under buoyancy, the complex floats upward to the water surface, forming a scum layer. At this time, the scum scraper 9 at the top of the tank is activated, pushing the scum layer into the scum chamber 8 through the scraper plate. The scum slides down the inclined guide plate in the scum chamber 8 and is finally discharged through the scum outlet 4. The purified water flows to the left and enters the clean water chamber 7. The clean water chamber 7 and the scum chamber 8 are isolated from each other to prevent the scum from flowing back and contaminating the clean water. Some of the purified water can be returned to the inlet of the transfer pump 11 through the circulation pipe head, mixed with the newly input extracted water, and then re-enter the dissolved air tank 12 to form a circulation treatment process and improve the dissolved air efficiency. The remaining purified water enters the effluent filtration and purification device 5 through the outlet 6 for deep purification. Multiple sludge outlets 3 at the bottom of the tank can periodically discharge the deposited sludge to prevent the accumulation of impurities at the bottom from affecting the treatment effect.

[0027] like Figure 1 , Figure 4 and Figure 5As shown, the left end of the outlet 6 is connected to an outlet filtration and purification device 5. The outlet filtration and purification device 5 includes a final discharge pipe 15, an outlet connection pipe 16, a cover handle 17, a sealing end cap 18, and a cuboid filtration and purification box 19. The cuboid filtration and purification box 19 is welded and fixed to the outer wall of the left end of the dissolved air flotation tank 1, and the top of the cuboid filtration and purification box 19 is open. The cuboid filtration and purification box 19 is located below the outlet 6. The outlet 6 is connected and fixed to the outlet connection pipe 16 at the left end by a flange and screws. The sealing end cap 18 is set inside the top opening of the cuboid filtration and purification box 19. The cover handle 17 is set at the center of the top of the sealing end cap 18. The final discharge pipe 15 is set at the rear end of the cuboid filtration and purification box 19 near the lower right corner. The final discharge pipe 15 is connected to the cuboid filtration and purification box 19. The interior of the box 19 is interconnected. The left half of the water outlet connecting pipe 16 is bent vertically downwards and inserted vertically into the left side of the center of the cuboid filter purification box 19. The bottom end of the left half of the water outlet connecting pipe 16 is close to the inner wall of the bottom of the cuboid filter purification box 19. The left side of the center of the sealing end cap 18 is provided with a sleeve hole, and the sealing end cap 18 is fitted onto the outside of the vertical section of the water outlet connecting pipe 16 through the sleeve hole. The sealing end cap 18 can be moved up and down by the opening handle 17. When closed, the bottom end is tightly attached to the top of the U-shaped fixing sleeve, forming a closed environment to prevent unfiltered water from overflowing from the top of the box. When opened, the filter screen can be quickly removed and installed through the opening handle 17 for easy cleaning or replacement, ensuring long-term stable filtration efficiency.

[0028] like Figure 1 , Figure 4 and Figure 5As shown, the water filtration and purification device 5 also includes a detachable filter screen 20. Multiple sets of U-shaped fixing sleeves are installed at the center of the inner walls at both ends of the cuboid filtration and purification box 19 and on its left and right sides. These U-shaped fixing sleeves are located between the vertical section of the water outlet connecting pipe 16 and the final discharge pipe 15, and each U-shaped fixing sleeve contains a detachable filter screen 20. After the sealing end cap 18 is closed into the opening at the top of the cuboid filtration and purification box 19, the bottom end of the sealing end cap 18 is tightly attached to the top of the multiple sets of U-shaped fixing sleeves. The multiple detachable filter screens 20 are stainless steel wire mesh filters, modified fiber ball filters, activated carbon filters, and precision pleated membrane filters. Water flowing from the outlet 6 is introduced into the box through the water outlet connecting pipe 16 (the left half of which bends vertically downwards to the bottom of the cuboid filtration and purification box 19). The water first contacts the first stainless steel wire mesh filter, which utilizes a relatively... Large mesh screens intercept large suspended impurities (such as silt particles and fibrous impurities) remaining in the water, preventing subsequent filters from becoming clogged and providing pretreatment protection. After initial filtration, the water enters the second modified fiber ball filter. The fiber balls, with their oleophilic properties and large specific surface area, remove residual emulsified oil, dispersed oil, and some fine suspended particles through adsorption and retention, significantly reducing the oil content of the water. Subsequently, the water flows into the third activated carbon filter. The porous structure of the activated carbon further adsorbs trace amounts of oil, organic pollutants (such as phenols and benzene compounds), and odor substances in the water, improving the sensory indicators and safety of the water. Finally, the water flows through the fourth precision pleated membrane filter, which traps extremely fine particles, colloids, and microorganisms remaining after the previous filtration, ensuring the accuracy of the effluent. The purified water is discharged through the final discharge pipe 15 and can be directly reused or discharged in compliance with standards.

[0029] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A high-efficiency dissolved air flotation device for oilfield produced water, comprising a dissolved air flotation tank (1) and a mounting base (2) disposed at the bottom of the dissolved air flotation tank (1), wherein the dissolved air flotation tank (1) and the mounting base (2) are fixedly connected by welding, wherein a dissolved air water release chamber (13) is disposed on the right side of the center of the dissolved air flotation tank (1), a clean water chamber (7) is disposed on the left side of the center of the dissolved air flotation tank (1), and a scum chamber (8) is disposed at the right end of the clean water chamber (7), wherein the scum chamber (8) and the clean water chamber (7) do not interfere with each other, and a scum scraper (9) is disposed at the middle section of the top of the dissolved air flotation tank (1), characterized in that: The dissolved air flotation tank (1) has an outlet (6) on the upper side of the center of the left end. The outlet (6) is connected to the interior of the water purification chamber (7). The outlet (6) is connected to the left end of the outlet (6) by an outlet filtration and purification device (5). The water filtration and purification device (5) includes a final discharge pipe (15), a water outlet connection pipe (16), a cover handle (17), a sealing end cap (18), and a cuboid filtration and purification box (19). The cuboid filtration and purification box (19) is welded and fixed to the outer wall of the left end of the dissolved air flotation tank (1), and the top of the cuboid filtration and purification box (19) is set with an opening. The cuboid filtration and purification box (19) is located below the water outlet (6). The left end of the water outlet (6) is connected and fixed to the water outlet connection pipe (16) by a flange and screws. The top opening of the cuboid filtration and purification box (19) is provided with a sealing end cap (18). The center of the top of the sealing end cap (18) is provided with a cover handle (17). The rear end of the cuboid filtration and purification box (19) is provided with a final discharge pipe (15) near the lower right corner. The final discharge pipe (15) is connected to the inside of the cuboid filtration and purification box (19).

2. The high-efficiency dissolved air flotation device for oilfield produced water according to claim 1, characterized in that: The left half of the water outlet connecting pipe (16) is bent vertically downwards and is vertically inserted into the left side of the center of the cuboid filter purification box (19). The bottom end of the left half of the water outlet connecting pipe (16) is close to the inner wall of the bottom end of the cuboid filter purification box (19). The left side of the center of the sealing end cap (18) is provided with a sleeve hole, and the sealing end cap (18) is sleeved on the outside of the vertical section of the water outlet connecting pipe (16) through the sleeve hole. The sealing end cap (18) can be moved up and down by the opening handle (17).

3. The high-efficiency dissolved air flotation device for oilfield produced water according to claim 2, characterized in that: The water filtration and purification device (5) also includes a detachable filter screen (20). Multiple sets of U-shaped fixing sleeves are provided at the center of the inner wall of the front and rear ends of the cuboid filtration and purification box (19) and on its left and right sides. The multiple sets of U-shaped fixing sleeves are located in the area between the vertical section of the water outlet connecting pipe (16) and the final discharge pipe (15). Each set of U-shaped fixing sleeves is inserted with a detachable filter screen (20). After the sealing end cap (18) is closed into the top opening of the cuboid filtration and purification box (19), the bottom end of the sealing end cap (18) is close to the top of the multiple sets of U-shaped fixing sleeves. The multiple detachable filter screens (20) are stainless steel wire mesh filter screen, modified fiber ball filter screen, activated carbon filter screen and precision pleated membrane filter screen, respectively.

4. The high-efficiency dissolved air flotation device for oilfield produced water according to claim 1, characterized in that: The dissolved air flotation tank (1) has a scum outlet (4) located near the upper left corner of the front end. The scum outlet (4) is located below the center of the front end of the scum chamber (8) and is connected to the interior of the scum chamber (8). When the scraper (9) is running, it can use the scraper plate to send the scum floating on the surface of the water inside the dissolved air flotation tank (1) into the scum chamber (8).

5. A high-efficiency dissolved air flotation device for oilfield produced water according to claim 4, characterized in that: An inclined guide plate is connected at the center of the rear inner wall of the scum chamber (8) to the bottom of the front inner wall. The scum inside the scum chamber (8) can be guided into the scum discharge outlet (4) and discharged through the inclined guide plate.

6. The high-efficiency dissolved air flotation device for oilfield produced water according to claim 1, characterized in that: An electrical control box (10) is fixed on the left side of the center of the outer wall at the rear end of the dissolved air flotation tank (1). A delivery pump (11) is provided on the right side of the electrical control box (10). A dissolved air tank (12) is provided on the right side of the delivery pump (11). A dissolved air water release device (14) is provided at the bottom of the interior of the dissolved air water release chamber (13).

7. A high-efficiency dissolved air flotation device for oilfield produced water according to claim 6, characterized in that: The inlet of the pump (11) is connected to the external oilfield produced water supply pipeline. The pump (11) can directly transport the oilfield produced water into the dissolved air tank (12) through the delivery pipe. The dissolved air tank (12) can transport the dissolved air water to the dissolved air water release device (14) through the delivery pipe. The dissolved air water release device (14) fully releases the dissolved air water into the dissolved air water release chamber (13), and the dissolved air water release chamber (13) is connected to the internal area of ​​the middle section of the dissolved air flotation tank (1).

8. A high-efficiency dissolved air flotation device for oilfield produced water according to claim 7, characterized in that: Multiple sludge discharge outlets (3) are provided on the lower side of the center of the outer wall of the front end of the dissolved air flotation tank (1). The multiple sludge discharge outlets (3) are all close to the bottom end of the dissolved air flotation tank (1). The multiple sludge discharge outlets (3) are respectively connected to the middle section area inside the dissolved air flotation tank (1), the water purification chamber (7) and the dissolved air water release chamber (13). The water purification chamber (7) is also connected to a circulation pipe head near the bottom rear end, and the circulation pipe head is connected to the inlet of the delivery pump (11) through the delivery pipe.

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