CN220201661U - Multi-stage treatment device for oil-water separation - Google Patents

Abstract

The utility model provides a multistage treatment device for oil-water separation, which comprises a primary treatment tank and a secondary treatment tank, wherein a connecting pipe connected with the secondary treatment tank is arranged on the primary treatment tank; wherein, a pretreatment filter element component is arranged in the primary treatment tank; a fine treatment filter element component is arranged in the secondary treatment tank; a support structure for supporting the pretreatment filter element assembly is arranged in the primary treatment tank; the tail end of the liquid inlet pipe is provided with a guide structure; the secondary treatment tank is internally provided with a sleeve which is covered outside the fine treatment filter element component, and the sleeve is provided with a secondary guide structure. Through the setting of guide structure and the setting of second grade guide structure, carry out drainage direction to oil field output liquid to the impact force that produces when the swirl mode entering reduces with jar body contact, thereby reduce the turbulent flow, guarantee oil-water separation efficiency, and can produce centrifugal force when the whirl, and then further improve oil-water separation efficiency.

Description

Multi-stage treatment device for oil-water separation

Technical Field

The utility model relates to the technical field of oil field produced liquid treatment, in particular to a multistage treatment device for oil-water separation.

Background

Through searching Chinese patent, application publication number: CN202022632386.1, patent name, in an oil-water separation pretreatment filter element component and an oil-water separation pretreatment device, a filter element is disclosed, the filter element adopts hydrophilic oleophobic glass fiber filter wires and oleophilic hydrophobic glass fiber filter wires as fillers, a filling layer is formed by stacking, the periphery wraps up the hydrophilic oleophobic filter wires and the protective screening, the obtained filter element performs oil-water separation in a mode of going out from the outside and going in from the inside, particulate matters and larger oil drops in the oil field produced liquid can be effectively trapped, emulsified oil in the oil field produced liquid can be removed, meanwhile, the filter element is not easy to be polluted, and the service life is long.

Through searching Chinese patent, application publication number: CN202022854035.5, the patent name is an oil-water separation fine treatment filter element component and the oil-water separation fine treatment device applied by the same, discloses a filter element, the filter element adopts a hydrophilic oleophobic glass fiber filter wire as a filler, which is wound on the pipe body of an inner pipe, the periphery is wrapped with a protective net, the obtained filter element is used for oil-water separation in an in-out mode, and is specially used for treating oil-in-water emulsion smaller than 20 μm, and is suitable for the fine treatment process after the oil-water separation pretreatment, the filter element is not only ensured to be difficult to be polluted, but also the demulsification of emulsified oil in water and the separation of tiny dispersed oil drops can be realized; in addition, the oil-water separation fine treatment device obtained by taking the filter element as a core component has the advantages of the filter element, can enrich and recycle oil drops, and has high recovery rate.

The utility model is found in the use process, the fact that the oilfield produced fluid directly impacts on the inner wall of the tank body when the oilfield produced fluid enters the treatment tank to form turbulence is not considered, so that the oilfield produced fluid is mixed again when entering the tank body, large oil drops are scattered to form small oil drops, the work load of the filter element is increased, and the oil-water separation efficiency is affected. The utility model therefore proposes a multistage treatment device for oil-water separation.

Disclosure of Invention

The utility model aims to provide a multi-and-treatment device for oil-water separation, which solves the problems that in the background art, when oil field output liquid enters a treatment tank, the oil field output liquid directly impacts on the inner wall of the tank body to form turbulence, so that the oil field output liquid is mixed again when entering the tank body, large oil drops are scattered to form small oil drops, the work load of a filter element is increased, and the oil-water separation efficiency is affected.

In order to achieve the above object, the present utility model provides a multistage treatment device for oil-water separation, comprising a primary treatment tank and a secondary treatment tank, a connecting pipe installed on the primary treatment tank and connected with the secondary treatment tank; the primary treatment tank is provided with a liquid inlet pipe communicated with the interior of the primary treatment tank; the tail end of the connecting pipe is communicated with the inside of the secondary treatment tank; oil outlets are arranged at the tops of the primary treatment tank and the secondary treatment tank; wherein, a pretreatment filter element component is arranged in the primary treatment tank; a fine treatment filter element component is arranged in the secondary treatment tank; a support structure for supporting the pretreatment filter element assembly is arranged in the primary treatment tank; the tail end of the liquid inlet pipe is provided with a guide structure; the secondary treatment tank is internally provided with a sleeve which is covered outside the fine treatment filter element component, and the sleeve is provided with a secondary guide structure.

Optionally, cylindrical sections are arranged at the bottoms of the inner cavities of the primary treatment tank and the secondary treatment tank; the pretreatment filter element component is arranged at the top of a cylinder section in the primary treatment tank and is communicated with the cylinder section; the fine treatment filter element component is arranged at the top of a cylinder section in the secondary treatment tank and is communicated with the cylinder section; the bottoms of the primary treatment tank and the secondary treatment tank are respectively provided with a tee joint part communicated with one port and the inner cavity of the shell ring; the bottom ends of the primary treatment tank and the secondary treatment tank are also provided with external cavity blow-down pipes.

Optionally, one of the ports of the tee is a drain outlet; one opening of the tee piece at the bottom of the primary treatment tank is a water outlet; one port of the tee piece at the bottom of the secondary treatment tank is a liquid inlet; and two ends of the connecting pipe are respectively connected with the water outlet and the liquid inlet.

Optionally, the guiding structure comprises a connecting bent pipe arranged at the tail end of the liquid inlet pipe and facing the pretreatment filter element assembly, a guiding straight pipe arranged at the tail end of the connecting bent pipe, and two guiding bent pipes arranged at the two ends of the guiding straight pipe; a sealing cover is arranged at the top of the cylinder sleeve; and a supporting disc is arranged in the cylinder sleeve, and an adapting hole adapted to the fine treatment filter element assembly is formed in the supporting disc.

Optionally, the distances from the two guide bent pipes to the connecting bent pipe are equal; the liquid outlet directions of the two guide bent pipes are opposite.

Optionally, bearing structure installs the stopper on the one-level treatment jar inner wall, installs the connecting block on the stopper and installs the spacing ring that is used for stabilizing pretreatment filter element assembly on the connecting block, is equipped with the through-hole with pretreatment filter element assembly looks adaptation on this spacing ring.

Optionally, the secondary guiding structure comprises two communicating straight pipes which are arranged on the sleeve and communicated with the inside of the sleeve, and a communicating bent pipe which is arranged at the tail end of the communicating straight pipe.

Optionally, the mounting positions of the two communicating straight pipes differ by 180 degrees; the included angle between the communicating bent pipe and the communicating straight pipe is smaller than 180 degrees, but not smaller than 90 degrees.

Optionally, the liquid outlet directions of the two communicating elbows are opposite.

Optionally, lifting lugs and safety valve mounting openings are arranged at the tops of the primary treatment tank and the secondary treatment tank; and a water outlet pipe is arranged on the side surface of the secondary treatment tank.

Compared with the prior art, the utility model provides a multistage treatment device for oil-water separation, which has the following beneficial effects:

according to the multistage treatment device for oil-water separation, through the arrangement of the guide structure, when oil field produced liquid enters the first-stage treatment tank, drainage and guide are carried out, so that the oil field produced liquid can not be directly washed out of the inner wall of the first-stage treatment tank, but enters the first-stage treatment tank in a cyclone mode, the included angle of the oil field produced liquid when the oil field produced liquid contacts with the inner wall of the first-stage treatment tank is smaller than 90 degrees, the impact force generated during contact is reduced, turbulence is reduced, large oil drops are prevented from being scattered, the load of a pretreatment filter element assembly is further reduced, and the oil-water separation efficiency is improved;

according to the multistage treatment device for oil-water separation, through the arrangement of the secondary guide structure, after the oil field produced liquid which is treated by the primary treatment tank is treated by the fine treatment filter element assembly, drainage guide is also carried out when the oil field produced liquid enters the secondary treatment tank for oil-water separation, so that the oil field produced liquid treated by the fine treatment filter element assembly is prevented from entering in a cyclone mode; the included angle of the oilfield produced fluid when the oilfield produced fluid contacts with the inner wall of the secondary treatment tank is smaller than 90 degrees, the impact force generated during contact is reduced, turbulence is reduced, the oil fluid and the water body are mixed again due to impact, oil-water separation efficiency is guaranteed, centrifugal force is generated during rotational flow, and oil-water separation efficiency is further improved.

Drawings

FIG. 1 is a schematic view of the overall structure of the present utility model;

FIG. 2 is a schematic diagram of the primary treatment tank of the present utility model;

FIG. 3 is an enlarged view of a portion of the utility model at A in FIG. 2;

FIG. 4 is a top view of the primary treatment tank of the present utility model;

FIG. 5 is a bottom view of the primary treatment tank of the present utility model;

FIG. 6 is a schematic view of a support structure of the present utility model;

FIG. 7 is a schematic view of the structure of the shell ring of the present utility model;

FIG. 8 is a schematic diagram of the secondary treatment tank of the present utility model;

FIG. 9 is a top view of the secondary treatment tank of the present utility model;

FIG. 10 is a bottom view of the secondary treatment tank of the present utility model;

fig. 11 is a schematic view of the structure of the support plate of the present utility model.

The marks in the figure are as follows: 1. a first-stage treatment tank; 11. a liquid inlet pipe; 12. a cylinder section; 13. an outer cavity blow-down pipe; 14. lifting lugs; 15. a safety valve mounting port; 2. a secondary treatment tank; 21. a sleeve; 22. a secondary guide structure; 221. a straight communicating pipe; 222. a communicating elbow; 23. a cover; 24. a support plate; 241. an adapter hole; 25. a water outlet pipe; 3. a connecting pipe; 4. an oil outlet; 5. preprocessing the filter element assembly; 6. finishing the filter element assembly; 7. a support structure; 71. a limiting block; 72. a connecting block; 73. a limiting ring; 731. a through hole; 8. a guide structure; 81. a connecting bent pipe; 82. a guide straight pipe; 83. a guide elbow; 9. a tee; 91. a sewage outlet; 92. a water outlet; 93. a liquid inlet.

Detailed Description

The following detailed description is made with reference to the accompanying drawings and detailed description. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present utility model. The present utility model may be embodied in many other forms than described herein and similarly generalized by those skilled in the art without departing from the spirit of the utility model and, therefore, the present utility model is not limited to the specific embodiments disclosed below.

The multistage treatment device for oil-water separation can be suitable for occasions such as oil-water separation of oilfield produced fluid, can be used for other similar application scenes, and is described in detail below.

Referring to fig. 1-11, a schematic structure of a multi-stage treatment device for oil-water separation according to the present utility model is shown. The multistage treatment device for oil-water separation comprises a primary treatment tank 1 and a secondary treatment tank 2, wherein a connecting pipe 3 connected with the secondary treatment tank 2 is arranged on the primary treatment tank 1; a liquid inlet pipe 11 communicated with the inner cavity of the primary treatment tank is arranged on the primary treatment tank 1; the tail end of the connecting pipe 3 is communicated with the inside of the secondary treatment tank 2; the tops of the primary treatment tank 1 and the secondary treatment tank 2 are respectively provided with an oil outlet 4; wherein, a pretreatment filter element component 5 is arranged in the primary treatment tank 1; a fine treatment filter element component 6 is arranged in the secondary treatment tank 2; a support structure 7 for supporting the pretreatment filter element assembly 5 is arranged in the primary treatment tank 1; the tail end of the liquid inlet pipe 11 is provided with a guide structure 8; a barrel sleeve 21 covered outside the fine treatment filter element assembly 6 is arranged in the secondary treatment tank 2, and a secondary guide structure 22 is arranged on the barrel sleeve 21; the pretreatment cartridge assembly 5 of the present utility model has been disclosed in publication number CN202022632386.1, patent name: the utility model patent of an oil-water separation pretreatment filter element component and an oil-water separation pretreatment device discloses that the specific structure of the pretreatment filter element component 5 is not repeated here; the refined filter element assembly 6 is disclosed in the utility model patent with publication number of CN202022854035.5 and patent name of an oil-water separation refined filter element assembly and an oil-water separation refined treatment device applied by the same, and the specific structure of the refined filter element assembly 6 is not repeated here; according to the utility model, through the arrangement of the supporting structure 7, the pretreatment filter element in the primary treatment tank 1 can be supported, so that when oil field produced fluid enters the primary treatment tank 1, excessive water flow impact is prevented, and the pretreatment filter element assembly 5 is loosened at the installation position, so that the pretreatment filter element assembly 5 cannot be used normally, the pretreatment filter element assembly 5 is limited and supported, the pretreatment filter element assembly 5 is prevented from shaking, the installation firmness of the pretreatment filter element assembly 5 is ensured, and the primary treatment tank 1 can be operated more stably; through the arrangement of the guide structure 8, the oilfield produced liquid is guided when entering the primary treatment tank 1, so that the oilfield produced liquid is not directly and vertically flushed on the inner wall of the primary treatment tank 1 by 90 degrees, but is in a rotational flow mode, the included angle between the oilfield produced liquid and the inner wall of the primary treatment tank 1 is smaller than 90 degrees, thereby reducing the turbulence generated by the oilfield produced liquid when contacting the inner wall, preventing large oil drops in the oilfield produced liquid from being scattered due to impact force to form oil drops to be mixed into emulsion, enabling the large oil drops to be layered with the emulsion, reducing the work load of the pretreatment filter element assembly 5 and improving the treatment efficiency; by the arrangement of the barrel sleeve 21, the emulsion passing through the pretreatment filter element assembly 5 and the fine treatment filter element assembly 6 is firstly subjected to oil-water separation in the barrel sleeve 21 and then flows out of the barrel sleeve 21, and is subjected to oil-water separation again in the secondary treatment tank 2, so that the oil-water separation effect is improved; through the setting of second grade guide structure 22 for the mixed solution that has carried out oil water separation in barrel casing 21 flows out in the barrel casing 21 through second grade guide structure 22, makes when flowing out, to this oil water mixture direction, reduces the impact force when this oil water mixture contacts with the second grade treatment jar 2 inner wall, reduces the turbulence that produces when contacting, reduces oil water separation's mixture and flows out, the degree that the profit mixes once more, thereby improves the oil water mixture oil water separation's in the second grade treatment jar efficiency.

Referring to fig. 1, 2, 7 and 8, in the utility model, cylindrical sections 12 are arranged at the bottoms of the inner cavities of a primary treatment tank 1 and a secondary treatment tank 2; the pretreatment filter element assembly 5 is arranged at the top of a shell ring 12 in the primary treatment tank 1 and is communicated with the shell ring 12; the fine treatment filter element assembly 6 is arranged at the top of a shell ring 12 in the secondary treatment tank 2 and is communicated with the shell ring 12; the bottoms of the primary treatment tank 1 and the secondary treatment tank 2 are respectively provided with a tee piece 9 communicated with one port and the inner cavity of the shell ring 12; the bottom ends of the primary treatment tank 1 and the secondary treatment tank 2 are also provided with external cavity blow-down pipes 13; according to the utility model, through the arrangement of the tube sections 12, the inner cavities of the primary treatment tank 1 and the secondary treatment tank 2 are divided into two areas, the two areas are communicated through the filter element assembly, namely, the inner area formed by the tube sections 12 in the primary treatment tank 1 is communicated with the area positioned outside the tube sections 12 in the inner cavity of the primary treatment tank 1 through the pretreatment filter element assembly 5, and the inner area formed by the tube sections 12 in the secondary treatment tank 2 is communicated with the area positioned outside the tube sections 12 in the inner cavity of the secondary treatment tank 2 through the fine treatment filter element assembly 6, so that liquid treated by the filter element assembly cannot be mixed with untreated liquid, and the treatment effect is ensured.

Referring to fig. 1, 2 and 8, in the present utility model, one of the ports of the tee 9 is a drain 91; one opening of the three-way piece 9 at the bottom of the primary treatment tank 1 is a water outlet 92; one port of the three-way piece 9 at the bottom of the secondary treatment tank 2 is a liquid inlet 93; two ends of the connecting pipe 3 are respectively connected with the water outlet 92 and the liquid inlet 93; by the arrangement of the technical scheme, the emulsion in the primary treatment tank 1 after being treated by the pretreatment filter element assembly 5 is discharged from the water outlet 92 and is treated by the fine treatment filter element assembly 6 in the secondary treatment tank 2, so that the emulsion is treated.

Referring to fig. 2, in the present utility model, the guide structure 8 includes a connecting elbow 81 installed at the end of the liquid inlet pipe 11 toward the pretreatment cartridge assembly 5, a guide straight pipe 82 installed at the end of the connecting elbow 81, and two guide elbow 83 installed at both ends of the guide straight pipe 82; a sealing cover 23 is arranged at the top of the barrel sleeve 21; a supporting disc 24 is arranged in the cylinder sleeve 21, and an adapting hole 241 adapted to the fine treatment filter element assembly 6 is arranged on the supporting disc 24; wherein, the distances from the two guide bent pipes 83 to the connecting bent pipe 81 are equal, and the liquid outlet directions of the two guide bent pipes 83 are opposite; according to the utility model, through the arrangement of the guide straight pipe 82, the oilfield produced fluid is divided into two parts averagely, compared with the situation that one part of fluid enters the primary treatment tank 1, the impact force of the oilfield produced fluid on the primary treatment tank 1 is reduced, so that turbulence generated when the oilfield produced fluid contacts the inner wall of the primary treatment tank 1 is reduced, and the degree of remixing of the fluid and the emulsion due to the impact force of the oilfield produced fluid is reduced; through the arrangement of the guide bent pipe 83, the contact angle of the oil field produced liquid and the inner wall of the first-stage treatment tank 1 is adjusted, so that the contact angle is smaller than 90 degrees, the impact force generated when the oil field produced liquid contacts the inner wall of the first-stage treatment tank 1 is reduced, the generated turbulence is reduced, and when the oil field produced liquid flows out, the oil field produced liquid exists in the first-stage treatment tank 1 in a cyclone mode, and centrifugal force exists, so that the separation effect of large oil drops and emulsion in the oil field produced liquid and the oil-water separation speed of a clamping block are improved; the position of the fine treatment filter element assembly 6 is supported and limited through the arrangement of the supporting disc 24, so that the shaking of the fine treatment filter element assembly 6 caused by overlarge impact force of liquid flow is prevented; by the arrangement of the adapting holes 241, the finishing filter element assembly 6 is avoided, so that the supporting disc 24 can be sleeved on the finishing filter element assembly 6.

Referring to fig. 2, in the present utility model, the distances from the two guide bent pipes 83 to the connecting bent pipe 81 are equal; the liquid outlet directions of the two guide bent pipes 83 are opposite; the utility model makes the distance from the guide bent pipe 83 to the connecting bent pipe 81 equal, so that the oilfield produced fluid divided into two streams is the same, and the guide effect on the oilfield produced fluid is the same; through the setting of the opposite liquid outlet direction of two guide return bend 83 for the direction of two oil field output liquid is opposite, but the whirl direction that produces is unanimous, clockwise whirl or anticlockwise whirl promptly, prevents that two oil field output liquids from bumping, forms turbulent flow when unable formation whirl, thereby guarantees that the oil field output liquid is the state of whirl in first order treatment jar 1, guarantees the oil water separation effect.

Referring to fig. 2-6, in the present utility model, a limiting block 71 of a supporting structure 7 installed on the inner wall of a primary treatment tank 1, a connecting block 72 installed on the limiting block 71, and a limiting ring 73 installed on the connecting block 72 for stabilizing a pretreatment filter element assembly 5, wherein a through hole 731 adapted to the pretreatment filter element assembly 5 is provided on the limiting ring 73; according to the utility model, the installation position of the connecting block 72 is limited by the arrangement of the limiting block 71; through the arrangement of the connecting blocks 72, the limiting block 71 can limit the limiting ring 73, and the limiting ring 73 is prevented from falling off; through the setting of spacing ring 73, cooperation through-hole 731 carries out spacingly to pretreatment filter core assembly 5, prevents that it from taking place to rock at the in-process of handling the emulsion.

Referring to fig. 9 to 11, in the present utility model, the secondary guide structure 22 includes two straight communicating pipes 221 disposed on the sleeve 21 and communicating with the inside of the sleeve 21, and a bent communicating pipe 222 mounted at the end of the straight communicating pipe 221; wherein, the installation positions of the two communicating straight pipes 221 differ by 180 degrees; the angle between the communication bent pipe 222 and the communication straight pipe 221 is less than 180 degrees, but not less than 90 degrees; the liquid outlet directions of the two communicating elbows 222 are opposite; according to the utility model, through the arrangement of the communication bent pipe 222, the oil-water mixture flowing out of the barrel sleeve 21 is guided, so that the oil-water mixture is not directly flushed on the inner wall of the secondary treatment tank 2 when flowing out, but is contacted with the inner wall of the secondary treatment tank 2 at a certain angle, centrifugal force exists, and after the oil-water mixture flows out of the barrel section 12, the oil-water mixture exists in the secondary treatment tank 2 in a cyclone mode, so that the oil-water separation efficiency is improved, the oil-water separation effect is ensured, the included angle between the communication bent pipe 222 and the communication straight pipe 221 is smaller than 180 degrees but not smaller than 90 degrees, the angle of the oil-water mixture when flowing out of the barrel sleeve 21 is changed, centripetal force is generated, the cyclone is formed after the oil-water mixture flows out, the separation efficiency of the oil-water mixture is improved, and the oil-water mixture separation effect is ensured.

Referring to fig. 2 and 9, in the utility model, lifting lugs 14 and a safety valve mounting port 15 are arranged at the tops of a primary treatment tank 1 and a secondary treatment tank 2; a water outlet pipe 25 is arranged on the side surface of the secondary treatment tank 2; according to the utility model, the lifting lugs 14 are arranged, so that the primary treatment tank 1 and the secondary treatment tank 2 are conveniently lifted, and workers can conveniently install the treatment tanks; the pressure inside the primary treatment tank 1 and the secondary treatment tank 2 is adjusted through the arrangement of the safety valve mounting port 15, so that the safety during use is ensured; the water layer after oil-water separation in the secondary treatment tank 2 can be smoothly discharged through the arrangement of the water outlet pipe 25.

Referring to fig. 1-11, the use process of the utility model is that firstly, the oilfield produced fluid flows to a connecting elbow pipe 81 through a fluid inlet pipe 11, the tail end of the connecting elbow pipe 81 is divided into two oilfield produced fluids to flow to two ends of a guide straight pipe 82, then the two oilfield produced fluids flow out of the guide elbow pipe 83 at two ends of the guide straight pipe 82, after the guidance of the guide elbow pipe 83, the flow direction angle of the two oilfield produced fluids is changed to generate centripetal force, so that the oilfield produced fluids flow out of the guide elbow pipe 83, vortex is formed in a primary treatment tank 1, and simultaneously, the centrifugal force and the centripetal force belong to interaction force, and the density of oil is lower than that of water in cooperation, so that the oil-water separation effect is improved, large-particle oil drops are converged to form an oil layer, and after the primary treatment tank 1 is full of oilfield produced fluids, the oil layer at the top is discharged from an oil outlet 4 at the top of the primary treatment tank 1; the emulsion formed by mixing small particle oil drops and water in the produced liquid of the oil field enters the shell ring 12 communicated with the pretreated filter element assembly 5 after being treated, then enters the connecting pipe 3 through the water outlet 92, flows into the shell ring 12 of the secondary treatment tank 2 through the liquid inlet 93, continuously rises along with the liquid level in the shell ring 12, the treated emulsion in the shell ring 12 enters the refined filter element assembly 6, the refined filter element assembly 6 again treats the emulsion, the oil-water mixture obtained after the treatment enters the shell sleeve 21 for oil-water separation and precipitation, continuously rises along with the continuous treatment of the refined filter element assembly 6 on the emulsion, flows into the communicating straight pipe 221 and flows out of the communicating bent pipe 222, and the communicating bent pipe 222 guides the flowing oil-water mixture at the moment, so that vortex is formed in the secondary treatment tank 2, and simultaneously the centrifugal force and the centripetal force belong to the interaction force, the density of the oil is lower than that of the water, thus the oil-water separation effect is improved, oil drops are converged at the top to form, the water layer is discharged from the top of the water outlet pipe 25 of the water outlet of the secondary treatment tank 2 after the secondary treatment tank 2 is fully treated, and the water outlet of the water outlet 25 from the top of the secondary treatment tank 2 is discharged from the top of the secondary treatment tank 2.

The above embodiments are illustrative of the present utility model, and not limiting, and any simple modifications of the present utility model fall within the scope of the present utility model.

Claims (10)

1. A multistage treatment device for oil-water separation comprises a primary treatment tank (1) and a secondary treatment tank (2), and a connecting pipe (3) which is arranged on the primary treatment tank (1) and connected with the secondary treatment tank (2); a liquid inlet pipe (11) communicated with the inside of the primary treatment tank is arranged on the primary treatment tank (1); the tail end of the connecting pipe (3) is communicated with the inside of the secondary treatment tank (2); an oil outlet (4) is arranged at the top of each of the primary treatment tank (1) and the secondary treatment tank (2); the pretreatment filter element assembly is characterized in that a pretreatment filter element assembly (5) is arranged in the primary treatment tank (1); a fine treatment filter element component (6) is arranged in the secondary treatment tank (2); a supporting structure (7) for supporting the pretreatment filter element assembly (5) is arranged in the primary treatment tank (1); the tail end of the liquid inlet pipe (11) is provided with a guide structure (8); the secondary treatment tank (2) is internally provided with a barrel sleeve (21) which is covered outside the fine treatment filter element assembly (6), and the barrel sleeve (21) is provided with a secondary guide structure (22).

2. The multistage treatment device for oil-water separation according to claim 1, wherein cylindrical sections (12) are arranged at the bottoms of the inner cavities of the primary treatment tank (1) and the secondary treatment tank (2); the pretreatment filter element assembly (5) is arranged at the top of a cylinder section (12) in the primary treatment tank (1) and is communicated with the cylinder section (12); the fine treatment filter element assembly (6) is arranged at the top of a cylinder section (12) in the secondary treatment tank (2) and is communicated with the cylinder section (12); the bottoms of the primary treatment tank (1) and the secondary treatment tank (2) are respectively provided with a tee joint (9) communicated with one port and the inner cavity of the shell ring (12); the bottom ends of the primary treatment tank (1) and the secondary treatment tank (2) are also provided with an outer cavity blow-down pipe (13).

3. The multistage treatment device for oil-water separation according to claim 2, characterized in that one of the ports of the tee (9) is a drain (91); one opening of the tee piece (9) at the bottom of the primary treatment tank (1) is a water outlet (92); one opening of the tee (9) at the bottom of the secondary treatment tank (2) is a liquid inlet (93); two ends of the connecting pipe (3) are respectively connected with the water outlet (92) and the liquid inlet (93).

4. The multistage treatment device for oil-water separation according to claim 1, wherein the guiding structure (8) comprises a connecting bent pipe (81) arranged at the tail end of the liquid inlet pipe (11) and facing the pretreatment filter element assembly (5), a guiding straight pipe (82) arranged at the tail end of the connecting bent pipe (81), and two guiding bent pipes (83) arranged at the two ends of the guiding straight pipe (82); a sealing cover (23) is arranged at the top of the cylinder sleeve (21); a supporting disc (24) is arranged in the cylinder sleeve (21), and an adapting hole (241) adapted to the fine treatment filter element assembly (6) is arranged on the supporting disc (24).

5. Multistage treatment device for oil-water separation according to claim 4, characterized in that the distance from two guide elbows (83) to a connecting elbows (81) is equal; the liquid outlet directions of the two guide bent pipes (83) are opposite.

6. The multistage treatment device for oil-water separation according to claim 1, wherein the supporting structure (7) is provided with a limiting block (71) arranged on the inner wall of the primary treatment tank (1), a connecting block (72) arranged on the limiting block (71) and a limiting ring (73) arranged on the connecting block (72) and used for stabilizing the pretreatment filter element assembly (5), and the limiting ring (73) is provided with a through hole (731) matched with the pretreatment filter element assembly (5).

7. The multistage treatment device for oil-water separation according to claim 1, wherein the secondary guiding structure (22) comprises two communicating straight pipes (221) arranged on the sleeve (21) and communicated with the interior of the sleeve (21), and a communicating bent pipe (222) arranged at the tail end of the communicating straight pipes (221).

8. The multistage treatment device for oil-water separation according to claim 7, characterized in that the installation positions of two said communicating straight pipes (221) differ by 180 °; the included angle between the communication bent pipe (222) and the communication straight pipe (221) is smaller than 180 degrees but not smaller than 90 degrees.

9. The multi-stage treatment device for oil-water separation according to claim 7, wherein the liquid outlet directions of the two communicating elbows (222) are opposite.

10. The multistage treatment device for oil-water separation according to claim 1, wherein lifting lugs (14) and a safety valve mounting port (15) are arranged at the tops of the primary treatment tank (1) and the secondary treatment tank (2); and a water outlet pipe (25) is arranged on the side surface of the secondary treatment tank (2).