Four-in-one oil and gas field sewage treatment device

Abstract

The invention relates to a four-in-one oil and gas field sewage treatment device, which comprises a sedimentation outer cylinder, a cylindrical air floatation inner cylinder, a sewage pipeline, an oil discharge pipe, a dissolved gas water injection system and a flocculation dosing system, the air floatation inner cylinder is arranged in the upper middle space of the sedimentation outer cylinder, one end of the oil discharge pipe extends to the upper part of the air floatation inner cylinder, and the other end of the oil discharge pipe downwards extends out of the sedimentation outer cylinder; a sewage inlet and an air inlet which are tangent to the inner wall of the air floatation inner cylinder penetrate through the side wall of the air floatation inner cylinder, a sewage pipeline is connected with the sewage inlet, an air-dissolved water injection system is connected with the air inlet, a flocculation dosing system is connected with the sewage pipeline, a sludge outlet is formed in the lower part of the sedimentation outer cylinder, a water outlet is formed in the upper part of the side wall of the sedimentation outer cylinder, and the sludge outlet is connected with the sewage inlet through a return pipeline. The device has the advantages that the structural design is simple and reasonable, rotational flow, air floatation, sedimentation and sludge dosing are integrated in one device, oil, water and solid phases can be efficiently separated, the structure is more compact, the effect (sludge backflow) of a medicament can be fully exerted, and the dosing amount is saved by more than 50%.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field wastewater pretreatment technology, and in particular to a four-in-one oil and gas field wastewater treatment device. Background Technology

[0002] Oil and gas field wastewater pretreatment generally includes equipment and methods such as chemical dosing, sedimentation, cyclone oil-water separation, and flotation. The main purpose is to separate most of the oil and suspended solids from the wastewater. Chemical dosing is typically a one-time addition. The sludge at the bottom of the tank after sedimentation contains a large amount of chemicals. Reusing part of the sludge at the bottom of the tank can optimize the dosing process and reduce the amount of chemicals needed. There are currently no reports on sludge reuse technology. Our laboratory research shows that sludge reuse can save more than 50% of the chemical dosage. Large tank sedimentation is a traditional method for separating oil, water, and solid phases using gravity. Due to its large size, it is mostly used in onshore oil and gas fields. Cyclone oil-water separators utilize the density difference between oil and water, and the centripetal acceleration (up to 1000-2000g) generated by high-speed rotation enables rapid oil-water separation. It is a highly efficient separation method, but high-speed rotation can easily lead to oil droplet emulsification, which negatively affects the oil-water separation effect. This is the key reason why it is difficult to widely promote and apply in oil and gas fields. Air flotation is a method that uses a dissolved air system to generate a large number of microbubbles in water, so that the gas attaches to oil and suspended particles in the form of highly dispersed microbubbles, creating a state where the density is less than that of water. It uses the principle of buoyancy to make them float on the water surface, thereby achieving the separation of oil, water and solid phases. However, air flotation equipment is large in size and has low efficiency, making it difficult to use in offshore oil and gas fields where space is limited.

[0003] Patents ZL201020213485.X and CN110902758B showcase single-stage or multi-stage cyclone flotation oil-water separation devices that combine micro-cyclone flow with air flotation, improving the compactness and efficiency of oil-water separation, but do not involve the removal of solids. Patent CN103145216B describes a two-stage cyclone flotation separator, the biggest difference from the above two patent technologies being the absence of guide vanes, and similarly lacking solids removal capabilities. Patent application CN102557322A discloses a multifunctional device integrating centripetal air flotation oil removal, eddy coagulation, and electrostatic scaling prevention, emphasizing the absence of chemical agents (flocculators). Practice has shown that without flocculants, only large oil droplets can be removed, while emulsified oil or small oil droplets cannot be removed. Patent application CN112759159A discloses a skid-mounted device that combines three processors (coarse, fine, and fine) in series, integrating turbulent flotation, filtration, and electrolytic cation removal principles. It has the function of separating oil, water, and solid phases, but it does not have the characteristics of being compact and efficient. Patent application CN110143684A discloses an ion flotation three-in-one purifier that integrates flotation and filtration into one tank. This makes it easy to cause difficulties in cleaning and replacing the filter media, resulting in filter media caking and loss of filtration effectiveness. Through visits to Changqing Oilfield, several sets of equipment in operation have all suffered serious failures.

[0004] Therefore, it is necessary to develop an oil and gas field wastewater treatment device that can overcome the above-mentioned technical problems. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a four-in-one oil and gas field wastewater treatment device, which effectively overcomes the defects of the prior art.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0007] A four-in-one oil and gas field wastewater treatment device includes a sedimentation outer cylinder, a cylindrical air flotation inner cylinder, a wastewater pipeline, an oil discharge pipe, a dissolved air water injection system, and a flocculation dosing system. The air flotation inner cylinder is located in the upper part of the sedimentation outer cylinder. One end of the oil discharge pipe extends above the air flotation inner cylinder, and the other end extends downward outside the sedimentation outer cylinder. The side wall of the air flotation inner cylinder is provided with a wastewater inlet and an air inlet tangent to its inner wall. The wastewater pipeline is connected to the wastewater inlet, the dissolved air water injection system is connected to the air inlet, and the flocculation dosing system is connected to the wastewater pipeline. The lower part of the sedimentation outer cylinder is provided with a sludge discharge port, and the upper part of the side wall of the sedimentation outer cylinder is provided with a water outlet. The sludge discharge port is connected to the wastewater inlet through a return pipeline.

[0008] Based on the above technical solution, the present invention can be further improved as follows.

[0009] Furthermore, the lower end of the aforementioned settling outer cylinder is cone-shaped, and the aforementioned sludge discharge port is located at the lower end of the side wall of the aforementioned settling outer cylinder near its bottom wall.

[0010] Furthermore, the aforementioned oil drain pipe is vertically installed, with its lower end penetrating the bottom walls of both the air flotation inner cylinder and the settling outer cylinder.

[0011] Furthermore, the upper end of the aforementioned oil drain pipe is provided with a trumpet-shaped oil inlet.

[0012] Furthermore, there are two sludge discharge ports, one of which is connected to the sewage inlet via a return pipeline, and a sludge return pump is installed on the return pipeline.

[0013] Furthermore, the dissolved gas water injection system includes a dissolved gas injection pipeline, one end of which is connected to the air inlet, and a dissolved gas pump is installed on the dissolved gas injection pipeline.

[0014] Furthermore, the other end of the dissolved gas injection pipeline is connected to the aforementioned water outlet.

[0015] Furthermore, the upper part of the inner wall of the aforementioned settling outer cylinder is provided with a downwardly extending water collection cylinder, and the aforementioned water outlet is located at the position corresponding to the upper end of the aforementioned water collection cylinder.

[0016] Furthermore, the aforementioned flocculation dosing system includes a dosing pipeline, with a dosing port on the wastewater pipeline, and one end of the dosing pipeline connected to a dosing tank.

[0017] Furthermore, sewage lift pumps are installed on the aforementioned sewage pipelines.

[0018] The beneficial effects of this invention are: the structural design is simple and reasonable, integrating cyclone, flotation, sedimentation and sludge dosing into one device, which can efficiently separate oil, water and solid phases, has a more compact structure, and can give full play to the effect of the agent (sludge return), saving more than 50% of the dosage. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of one embodiment of the four-in-one oil and gas field wastewater treatment device of the present invention.

[0020] Figure 2 This is a cross-sectional view of the air flotation inner cylinder in the four-in-one oil and gas field wastewater treatment device of the present invention;

[0021] Figure 3 This is a schematic diagram of another embodiment of the four-in-one oil and gas field wastewater treatment device of the present invention;

[0022] Figure 4 This is a schematic diagram of another embodiment of the four-in-one oil and gas field wastewater treatment device of the present invention;

[0023] Figure 5 This is a schematic diagram of another embodiment of the four-in-one oil and gas field wastewater treatment device of the present invention;

[0024] Figure 6 This is a schematic diagram of another embodiment of the four-in-one oil and gas field wastewater treatment device of the present invention;

[0025] Figure 7 This is a schematic diagram of an embodiment of the four-in-one oil and gas field wastewater treatment device of the present invention with a cover.

[0026] The attached diagram lists the components represented by each number as follows:

[0027] 1. Settling outer cylinder; 2. Flotation inner cylinder; 3. Sewage pipeline; 4. Oil discharge pipe; 5. Return pipeline; 11. Sludge discharge port; 12. Water outlet; 13. Water collection cylinder; 21. Sewage inlet; 22. Air inlet; 31. Sewage lift pump; 51. Sludge return pump; 61. Dissolved air injection pipeline; 62. Dissolved air pump; 71. Chemical dosing pipeline; 72. Chemical dosing tank. Detailed Implementation

[0028] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0029] Example: Figure 1 and 2 As shown, the four-in-one oil and gas field wastewater treatment device of this embodiment includes a sedimentation outer cylinder 1, a cylindrical air flotation inner cylinder 2, a wastewater pipeline 3, an oil discharge pipe 4, a dissolved air water injection system, and a flocculation dosing system. The air flotation inner cylinder 2 is located in the upper part of the sedimentation outer cylinder 1. One end of the oil discharge pipe 4 extends above the air flotation inner cylinder 2, and the other end extends downward outside the sedimentation outer cylinder 1. The side wall of the air flotation inner cylinder 2 is provided with a wastewater inlet 21 and an air inlet 22 tangent to its inner wall. The wastewater pipeline 3 is connected to the wastewater inlet 21. The dissolved air water injection system is connected to the air inlet 22. The flocculation dosing system is connected to the wastewater pipeline 3. The lower part of the sedimentation outer cylinder 1 is provided with a sludge discharge port 11, and the upper part of the side wall of the sedimentation outer cylinder 1 is provided with a water outlet 12. The sludge discharge port 11 is connected to the wastewater inlet 21 through a return pipeline 5.

[0030] In this embodiment, the four-in-one oil and gas field wastewater treatment device adds flocculant through a flocculation dosing system simultaneously with the incoming wastewater from the wastewater pipeline 3. This causes small oil droplets in the wastewater to coalesce into larger oil droplets and small solid particles to coalesce into larger solid particles. Afterward, the wastewater from the pipeline 3 is fed into the air flotation inner cylinder 2. Simultaneously, dissolved air water is injected into the air flotation inner cylinder 2 through a dissolved air water injection system. Since both the wastewater inlet 21 and the air inlet 22 enter tangentially along the inner wall of the air flotation inner cylinder 2, a swirling flow field with a centripetal acceleration of 8-20g is generated within the air flotation inner cylinder 2. A large number of 5-30μm (diameter) bubbles precipitate from the dissolved air water, fully mixing and contacting the oil droplets in the swirling flow field, carrying the oil droplets rapidly towards the upper center of the air flotation inner cylinder 2. The wastewater accumulates at one end and then enters through one end of the oil drain pipe 4, and exits through the other end of the oil drain pipe 4 outside the settling outer cylinder 1. During this process, the wastewater spreads from the upper part of the air flotation inner cylinder 2 into the settling outer cylinder 1, the swirling field gradually disappears, the water flow changes from a turbulent state to a laminar state, and the solids in the water begin to settle and deposit at the bottom of the settling outer cylinder 1 to form sludge. The sludge flows back to the air flotation inner cylinder 2 through the sludge discharge port 11, the return pipeline 5 and the wastewater inlet 21. The flocculant contained in the sludge plays a flocculation role again and flocculates with the oil and solids in the wastewater again. Therefore, the amount of flocculant added to the flocculation dosing system can be reduced. Experiments have shown that sludge reuse can save more than 50% of the amount of flocculant added. The clear water after settling can flow out through the outlet 12. The entire device has a simple and reasonable structural design, integrating cyclone, flotation, sedimentation, and sludge dosing into one device. It can efficiently separate oil, water, and solid phases, has a more compact structure, and can fully utilize the effect of the chemicals (sludge return), saving more than 50% of the dosage. The effect is very good and has high economic benefits.

[0031] It should be further explained that in this embodiment, the wastewater and dissolved air water enter the lower end of the side wall of the air flotation inner cylinder 2 tangentially, forming a swirling air flotation with microgravity acceleration (centripetal acceleration 8-20g) inside the air flotation inner cylinder 2. The microgravity acceleration can accelerate the separation of oil, water and solid phases on the one hand, and protect the flocs formed by flocculation on the other hand, so that they do not break and affect the separation effect.

[0032] In this embodiment, the outer settling cylinder 1 is also a cylinder with a circular cross-section, or a cylinder (with a conical lower end). The diameter of the inner air flotation cylinder 2 is 25%-35% of the upper diameter of the outer settling cylinder 1, and the height is 70%-80% of the height of the outer settling cylinder 1.

[0033] In a preferred embodiment, the lower end of the settling outer cylinder 1 is cone-shaped, and the sludge discharge port 11 is located at the lower end of the side wall of the settling outer cylinder 1 near its bottom wall.

[0034] In the above implementation scheme, the settling outer cylinder 1 has a shape that is larger at the top and smaller at the bottom, which can promote the sludge after settling to gather at the bottom along the lower conical surface of the settling outer cylinder 1, ensuring good sludge return and avoiding poor return due to sludge dispersion.

[0035] In this embodiment, the oil drain pipe 4 is vertically arranged, with its lower end penetrating the bottom walls of both the air flotation inner cylinder 2 and the settling outer cylinder 1. The oil drain pipe 4 is a vertical pipe, which facilitates the discharge of oil under gravity. At the same time, the layout of the oil drain pipe 4 is also relatively simple, using a downward insertion method to optimize space utilization.

[0036] As a preferred implementation method, such as Figure 3 As shown, the upper end of the above-mentioned oil drain pipe 4 is provided with a trumpet-shaped oil inlet (a in the figure).

[0037] In the above implementation scheme, the funnel-shaped oil inlet design facilitates the proper discharge of the air-float oil.

[0038] As a preferred implementation method, such as Figure 4 As shown, there are two sludge discharge ports 11. One of the sludge discharge ports 11 is connected to the sewage inlet 21 through the return pipeline 5. The return pipeline 5 is equipped with a sludge return pump 51.

[0039] In the above implementation scheme, two sludge discharge ports 11 are designed, one of which can discharge sludge normally, and the other can realize the return of sludge, making the use more flexible.

[0040] In a preferred embodiment, the dissolved air water injection system includes a dissolved air injection pipeline 61, one end of which is connected to the air inlet 22, and a dissolved air pump 62 is provided on the dissolved air injection pipeline 61.

[0041] In the above implementation scheme, the dissolved air pump 62 draws liquid source connected to the dissolved air injection pipeline 61, and forms dissolved air water with the intake air, which is then sent into the air flotation inner cylinder 2 to ensure the good preparation and delivery of dissolved air water.

[0042] As a preferred implementation method, such as Figure 5 As shown, the other end of the dissolved air injection pipeline 61 is connected to the water outlet 12.

[0043] In the above implementation scheme, the outlet 12 of the dissolved air injection pipeline 61 makes full use of the clean water source after sewage treatment for recycling, effectively saving water resources.

[0044] As a preferred implementation method, such as Figure 6 As shown, the upper part of the inner wall of the sedimentation outer cylinder 1 is provided with a downwardly extending water collection cylinder 13, and the water outlet 12 is provided at the part corresponding to the upper end of the water collection cylinder 13.

[0045] In the above implementation scheme, the design of the water collection cylinder 13 facilitates the discharge of clean water, and the thickness of the annular cavity between the side wall of the water collection cylinder 13 and the sedimentation outer cylinder 1 is relatively narrow, which can suppress the entry of overflowing air bubbles.

[0046] In this embodiment, the above-mentioned flocculation dosing system includes a dosing pipeline 71. The sewage pipeline 3 is provided with a dosing port. One end of the dosing pipeline 71 is connected to the dosing tank 72. The dosing pipeline 71 is connected to the sewage pipeline 3 with a control valve. The dosing pipeline 71 is generally connected above the sewage pipeline 3. The dosing tank 72 is filled with flocculant. After the control valve is opened, the flocculant can enter the sewage pipeline 3 under the action of gravity and enter the air flotation inner cylinder 2 along with the sewage pipeline 3.

[0047] In this embodiment, a sewage lift pump 31 is provided on the sewage pipeline 3 to ensure that sewage is well transported into the air flotation inner cylinder 2.

[0048] In this embodiment, the discharge capacity of the sludge return pump 51 is 5%-12% of the discharge capacity of the sewage lift pump 31. The discharge capacity of the dissolved air pump 62 is 15%-30% of the discharge capacity of the sewage lift pump 31.

[0049] It should be noted that in this embodiment, the return pipeline 5 can be connected to the sewage pipeline 3 (specifically, connected to the pipeline where the outlet of the sewage lift pump 31 is located), the dosing pipeline 71 is connected to the pipeline at the inlet of the sewage lift pump 31, and the head of the sludge return pump 51 is more than 20% higher than the head of the sewage lift pump 31.

[0050] In this embodiment, an openable or closable cover plate (such as...) can be provided at the upper end of the settling outer cylinder 1. Figure 7 As shown in the figure (b refers to the cover plate), a flushing pipeline and a flushing nozzle are installed at the lower end of the cover plate.

[0051] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to 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 invention.

[0052] Furthermore, 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. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0053] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," 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, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0054] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0055] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0056] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A four-in-one oil and gas field wastewater treatment device, characterized in that: The system includes a settling outer cylinder (1), a cylindrical air flotation inner cylinder (2), a sewage pipeline (3), an oil drain pipe (4), a dissolved air water injection system, and a flocculation dosing system. The air flotation inner cylinder (2) is located in the upper part of the settling outer cylinder (1). One end of the oil drain pipe (4) extends above the air flotation inner cylinder (2), and the other end extends downward outside the settling outer cylinder (1). A sewage inlet (2) tangential to the inner wall of the air flotation inner cylinder (2) is provided through the side wall of the air flotation inner cylinder (2). 1) and air inlet (22), the sewage pipeline (3) is connected to the sewage inlet (21), the dissolved air water injection system is connected to the air inlet (22), the flocculation dosing system is connected to the sewage pipeline (3), the sedimentation outer cylinder (1) is provided with a sludge discharge port (11) at the bottom, the sedimentation outer cylinder (1) is provided with a water outlet (12) at the upper side wall, and the sludge discharge port (11) is connected to the sewage inlet (21) through a return pipeline (5).

2. The four-in-one oil and gas field wastewater treatment device according to claim 1, characterized in that: The lower end of the settling outer cylinder (1) is cone-shaped, and the sludge discharge port (11) is located at the lower end of the side wall of the settling outer cylinder (1) near its bottom wall.

3. The four-in-one oil and gas field wastewater treatment device according to claim 1, characterized in that: The oil drain pipe (4) is set vertically, and its lower end passes through the bottom walls of both the air flotation inner cylinder (2) and the settling outer cylinder (1).

4. The four-in-one oil and gas field wastewater treatment device according to claim 3, characterized in that: The upper end of the oil drain pipe (4) is provided with a trumpet-shaped oil inlet.

5. The four-in-one oil and gas field wastewater treatment device according to claim 1, characterized in that: There are two sludge discharge ports (11), one of which is connected to the sewage inlet (21) through the return pipeline (5). The return pipeline (5) is equipped with a sludge return pump (51).

6. The four-in-one oil and gas field wastewater treatment device according to claim 1, characterized in that: The dissolved air water injection system includes a dissolved air injection pipeline (61), one end of which is connected to the air inlet (22), and a dissolved air pump (62) is provided on the dissolved air injection pipeline (61).

7. The four-in-one oil and gas field wastewater treatment device according to claim 6, characterized in that: The other end of the dissolved air injection pipeline (61) is connected to the water outlet (12).

8. The four-in-one oil and gas field wastewater treatment device according to claim 7, characterized in that: The upper part of the inner wall of the settling outer cylinder (1) is provided with a downwardly extending water collection cylinder (13), and the water outlet (12) is located at the upper part of the water collection cylinder (13).

9. The four-in-one oil and gas field wastewater treatment device according to claim 1, characterized in that: The flocculation dosing system includes a dosing pipeline (71), and a dosing port is provided on the sewage pipeline (3). One end of the dosing pipeline (71) is connected to the dosing tank (72).

10. A four-in-one oil and gas field wastewater treatment device according to any one of claims 1 to 9, characterized in that: The sewage pipeline (3) is equipped with a sewage lift pump (31).

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