A coalescing filter tank for treating oily wastewater

Abstract

The present invention discloses a coalescing filter tank for treating oily wastewater, which relates to the technical field of filter tanks and solves the technical problems that in the process of treating oily wastewater, when there is a large amount of oily wastewater, the single filtration area has a small wastewater treatment capacity and the filtration is not clean enough; it includes: a tank body, and the interior of the tank body is partitioned into a left filtration area I, a middle pretreatment area, and a right filtration area II from left to right in sequence; the middle pretreatment area includes a hydrocyclone vertically installed in the middle position of the tank body, and a plurality of separation inclined plates for separating oil and water are arranged above the hydrocyclone, and the water separated from the middle pretreatment area enters the left filtration area I and the right filtration area II respectively; through the first method of treating oil and water by the cooperation of the left filtration area I, the middle pretreatment area, and the right filtration area II, the present invention increases the filtration treatment process, can realize the multi-stage filtration treatment of wastewater, improves the treatment effect on oily wastewater, and ensures that the treated water quality index is qualified.

Description

Technical Field

[0001] The present invention belongs to the technical field of filter tanks, and specifically relates to a coalescing filter tank for treating oily wastewater. Background Art

[0002] Oily wastewater is a type of wastewater generated during oil exploration and production. Oily wastewater has complex components, high oil content, and high salinity. If it is directly reinjected without treatment, it will cause equipment damage and pipeline or formation blockage, affecting safe production; if it is directly discharged into the soil, it will affect the activity of soil microorganisms and also cause pollution to water bodies and the atmosphere. Therefore, filter tanks are used to purify oily wastewater.

[0003] In the treatment of oily wastewater by some existing filter tanks, when the oil content of the wastewater is high, the filter bed and filter element are easily contaminated and blocked, and it is difficult to restore the performance of the filter material and filter element even through backwashing; when the incoming water volume suddenly increases, a single filtration area cannot meet the production requirements, the pressure is high, and the filtration is not clean; when the filter element is dirty, it is necessary to stop work to replace the filter element, and only after the replacement is completed can the filter be used to treat oily wastewater again, resulting in a relatively large shutdown cost. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art; for this purpose, the present invention proposes a coalescing filter tank for treating oily wastewater.

[0005] A coalescing filter tank for treating oily wastewater, comprising:

[0006] A tank body, the interior of which is sequentially divided into a left filtration area one, a middle pretreatment area, and a right filtration area two from left to right;

[0007] The middle pretreatment area includes a hydrocyclone vertically installed in the middle of the tank body. Above the hydrocyclone, there are multiple separation inclined plates for oil-water separation. The water separated from the middle pretreatment area enters the left filtration area one and the right filtration area two respectively, and is filtered by the filter bed and filter element arranged in the left filtration area one and the right filtration area two.

[0008] Preferably, the middle pretreatment area further includes a first water inlet arranged on the front surface of the tank body. The rear end of the first water inlet is communicated with the hydrocyclone and supplies water to the interior of the hydrocyclone.

[0009] Preferably, the middle pretreatment area further includes a partition plate horizontally installed on the inner wall of the tank body and located at the upper end of the hydrocyclone. A small number of water delivery holes are opened on the upper surface of the partition plate.

[0010] Preferably, a wastewater cavity is formed between the hydrocyclone, the partition plate, and the inner wall of the tank body. A first water outlet communicated with the water cavity is arranged at the bottom of the tank body.

[0011] Preferably, the left filtration zone I and the right filtration zone II have the same structure. The left filtration zone I includes:

[0012] A filter bed horizontally installed inside the tank body. A guiding inclined plate is arranged inside the tank body below the filter bed. A water storage cavity is formed between the lower surface of the guiding inclined plate and the inner wall of the tank body;

[0013] A second water inlet installed on the upper surface of the left end of the tank body. A left water pipe is arranged between the second water inlet and the first water outlet;

[0014] A third water inlet installed on the upper surface of the right end of the tank body. A right water pipe is arranged between the third water inlet and the first water outlet;

[0015] And two groups of filter elements longitudinally distributed between the lower part of the guiding inclined plate and the inner wall of the tank body.

[0016] Preferably, a plurality of water passing holes are formed on the surface of the guiding inclined plate. A second water outlet communicated with the filter element is arranged on the lower surface of the left end of the tank body;

[0017] A third water outlet communicated with the filter element is arranged on the lower surface of the right end of the tank body.

[0018] Preferably, the left filtration zone I further includes a water distribution pipe located above the filter bed. The water distribution pipe is connected to the second water inlet, and a plurality of water distribution ports are evenly formed on the surface of the water distribution pipe.

[0019] Preferably, a flushing structure for cleaning the filter media in the filter bed is arranged inside both the left filtration zone I and the right filtration zone II. The flushing structure includes:

[0020] A scrubbing barrel for cleaning the filter media;

[0021] A cloth barrel extending above the filter bed. The cloth barrel is in a Y shape, and the cloth outlet at its lower end extends towards both ends of the filter bed;

[0022] A left electric valve I and a right electric valve II for controlling the filter media in the scrubbing barrel to enter the cloth barrel;

[0023] And a backwashing discharge port installed at the bottom of the tank body. The backwashing discharge port is located between the two guiding inclined plates.

[0024] Preferably, the flushing structure further includes a sewage discharge pipe communicated with the inside of the scrubbing barrel. A valve IX is arranged on the sewage discharge pipe.

[0025] Preferably, an oil collection device communicated with the left filtration zone I, the middle pretreatment zone and the right filtration zone II respectively is arranged at the top of the tank body. An oil-water interface instrument is arranged at the top of the oil collection device, and an oil collection pipe is arranged between a plurality of oil collection devices.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) By adding a middle pretreatment area in the left filtration area I and the right filtration area II, most of the oil in the oily wastewater can be removed through a hydrocyclone, reducing the pollution of the oil to the subsequent filter bed and filter element.

[0028] (2) Through the first method of treating oily water by the cooperation of the left filtration area I, the middle pretreatment area, and the right filtration area II, the filtration treatment process is increased, and multi-stage filtration treatment of the wastewater can be realized, improving the treatment effect and cleanliness of the oily wastewater, and ensuring that the treated water quality index is qualified.

[0029] (3) Through the second method of treating oily water by the cooperation of the middle pretreatment area with the left filtration area I and the right filtration area II, the wastewater treatment capacity is large, and emergency treatment of a sudden increase in the front-end wastewater can be realized.

[0030] (4) Through the third method of treating oily water by the cooperation of the left filtration area I, the middle pretreatment area, and the right filtration area II, when the filter element in the left filtration area I or the right filtration area II is dirty and needs to be replaced, the left filtration area I or the right filtration area II can work independently, ensuring continuous treatment of the oily wastewater, avoiding the trouble of the entire filter tank shutting down for filter element replacement, reducing the shutdown cost, and improving the continuous filtration or treatment effect of the oily wastewater.

[0031] (5) Through the fourth method of treating oily water by the cooperation of the left filtration area I, the middle pretreatment area, and the right filtration area II, when the filter material in the left filtration area I is being cleaned, the wastewater in the middle pretreatment area first enters the left filtration area I for filtration through the first water outlet, and the filtered water in the left filtration area I then enters the right filtration area II for filtration through the second water outlet, realizing the synchronous progress of filter material cleaning and multi-stage treatment, and achieving efficient treatment of the oily wastewater.

[0032] (6) Through the fifth method of treating oily water by the cooperation of the left filtration area I, the middle pretreatment area, and the right filtration area II, when the filter material in the right filtration area II is being cleaned, the wastewater in the middle pretreatment area first enters the right filtration area II for filtration through the first water outlet, and the filtered water in the right filtration area II then enters the left filtration area I for filtration through the third water outlet, realizing the synchronous progress of filter material cleaning and multi-stage treatment, and achieving efficient treatment of the oily wastewater. Brief Description of the Drawings

[0033] Figure 1 It is a schematic structural diagram of the wastewater treatment process of the filter tank of the present invention;

[0034] Figure 2 For the present invention Figure 1 It is a schematic structural diagram of the middle pretreatment area in the present invention;

[0035] Figure 3 For the present inventionFigure 1 Enlarged view of area A;

[0036] Figure 4 For the present invention Figure 1 Schematic structural diagram of the water distribution pipe;

[0037] Figure 5 For the present invention Figure 1 Schematic structural diagram of the flushing structure;

[0038] In the figure: 1, tank body; 2, cyclone; 3, first water inlet; 4, partition board; 5, separation inclined plate; 6, first water outlet; 7, right water pipe; 8, second water outlet; 9, filter element; 10, left water pipe; 11, guiding inclined plate; 12, filter bed; 13, second water inlet; 14, sewage discharge pipe; 15, oil collection pipe; 16, oil-water interface meter; 17, flushing structure; 18, sewage discharge port; 19, water distribution pipe; 20, backwashing discharge port; 21, scrubbing barrel; 22, cloth barrel; 23, valve eight; 24, valve six; 25, valve three; 26, valve five; 27, valve seven; 28, valve nine; 29, valve thirteen; 30, valve one; 31, valve two; 32, valve four; 33, third water inlet; 34, third water outlet; 35, electric valve one; 36, electric valve two. Specific embodiments

[0039] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0040] Embodiment 1

[0041] Please refer to Figure 1 - Figure 3 , this application provides a coalescing filter tank for treating oily wastewater, including:

[0042] Tank body 1, the interior of the tank body 1 is divided into a left filter zone 1, a middle pretreatment zone, and a right filter zone 2 from left to right in sequence;

[0043] The middle pretreatment area includes a hydrocyclone 2 vertically installed at the middle position of the tank body 1. Above the hydrocyclone 2, there are multiple groups of separation inclined plates 5 for oil-water separation. Wastewater enters the hydrocyclone 2 through the first water inlet 3. The hydrocyclone 2 is used to facilitate the rapid separation of oil and water. Oil flows out from the upper middle part of the hydrocyclone 2 and is dehydrated by the separation inclined plates 5. The water separated from the middle pretreatment area enters the left filtration area one and the right filtration area two respectively and is filtered by the filter beds 12 arranged in the left filtration area one and the right filtration area two. The middle pretreatment area also includes the first water inlet 3 arranged on the front surface of the tank body 1. The rear end of the first water inlet 3 is communicated with the hydrocyclone 2 and supplies water to the inside of the hydrocyclone 2.

[0044] In this embodiment, preferably, the middle pretreatment area also includes a partition plate 4 horizontally installed on the inner wall of the tank body 1 and located at the upper end of the hydrocyclone 2. The water on the separation inclined plates 5 can flow downward along its inclined surface and fall into the wastewater cavity through the water delivery holes. A small number of water delivery holes are opened on the upper surface of the partition plate 4. The setting of the water delivery holes can ensure that when the incoming liquid fluctuates, the upper separation inclined plates 5 are not impacted, which is convenient for the wastewater separated by the separation inclined plates 5 to re-enter the wastewater cavity and improves the oil removal effect of the wastewater.

[0045] In this embodiment, preferably, a wastewater cavity is formed between the hydrocyclone 2, the partition plate 4 and the inner wall of the tank body 1. A first water outlet 6 communicated with the water cavity is arranged at the bottom of the tank body 1, which is convenient for discharging the pretreated wastewater.

[0046] In summary, the incoming water first enters the hydrocyclone 2 through the first water inlet 3. In the hydrocyclone 2, the water moves downward and flows out from the lower part of the hydrocyclone 2, while the oil flows out from the upper part of the hydrocyclone 2 and is dehydrated by the separation inclined plates 5. The oil is collected by the oil collection device along the upward direction of the separation inclined plates 5, and the water on the separation inclined plates 5 flows downward along the inclined surface, passes through the water delivery holes on the partition plate 4 and enters the wastewater cavity. The left filtration area one, the middle pretreatment area and the right filtration area two cooperate in the first way of treating oil and water. The water flowing out from the lower part of the hydrocyclone 2 enters the wastewater cavity and then is discharged from the first water outlet 6, passes through the valve two 31 and the left water pipe 10 and enters the second water inlet 13 in the left filtration area one, and falls on the filter bed 12 through the water distribution openings on the water distribution pipe 19 and is filtered by the filter media in the filter bed 12. The preliminarily filtered wastewater passes through the guiding inclined plate 11 and enters the filter element 9 for treatment. After being filtered by the filter element 9, the purified water passes through the valve five 26, then passes through the valve four 32 and the extended drain pipe and enters the second water inlet 13 in the right filtration area two, and then flows downward after being filtered by the right filter bed 12. After being filtered by the right guiding inclined plate 11 and the filter element 9, the secondary purified water can be transported out through the valve eight 23. In the first way, by adding filtration treatment procedures, multi-stage filtration treatment of the wastewater can be realized, the treatment effect and cleanliness of the oily wastewater can be improved, and the qualified treatment water quality index can be ensured.

[0047] In summary, the incoming water first enters the hydrocyclone 2 through the first water inlet 3. In the hydrocyclone 2, the water moves downward and flows out from the lower part of the hydrocyclone 2, while the oil flows out from the upper part of the hydrocyclone 2 and is then dehydrated by the separation inclined plate 5. The oil is collected by the oil collecting device along the upward direction of the separation inclined plate 5, and the water on the separation inclined plate 5 flows downward along the inclined surface, passes through the water conveyance holes on the partition plate 4 and enters the wastewater chamber. This is the second method for the middle pretreatment area to cooperate with the left filtration area 1 and the right filtration area 2 in treating oil and water. The water flowing out from the lower part of the hydrocyclone 2 enters the wastewater chamber and then is discharged from the first water outlet 6. It enters the second water inlet 13 in the left filtration area 1 and the third water inlet 33 in the right filtration area 2 in parallel through the valve 1 30, the valve 2 31, the left water pipe 10 and the right water pipe 7, and falls on the filter bed 12 through the water distribution openings on the water distribution pipe 19. The wastewater is filtered by the filter media in the filter bed 12. The preliminarily filtered wastewater passes through the guiding inclined plate 11 and enters the filter element 9 for treatment. After being filtered by the filter element 9, the purified water can be conveyed out through the valve 7 27 and the valve 8 23. In the second method, the wastewater treatment capacity is large, and it can realize the emergency treatment of a sudden increase in the front-end wastewater.

[0048] Embodiment 2

[0049] Referring to Figure 1 、 Figure 4 and Figure 5 , this is the second embodiment of the present invention.

[0050] In this embodiment, preferably, the left filtration area 1 and the right filtration area 2 have the same structure. The left filtration area 1 includes:

[0051] The filter bed 12 horizontally installed inside the tank body 1. There is a guiding inclined plate 11 arranged inside the tank body 1 below the filter bed 12. A water storage cavity is formed between the lower surface of the guiding inclined plate 11 and the inner wall of the tank body 1;

[0052] The second water inlet 13 installed on the upper surface of the left end of the tank body 1, which is convenient for sending the wastewater discharged from the middle pretreatment area into the left filtration area 1 for treatment. There is a left water pipe 10 arranged between the second water inlet 13 and the first water outlet 6. A valve 2 31 is arranged on the left water pipe 10. Drainage ports 18 are arranged at both the left and right bottoms of the tank body 1;

[0053] The third water inlet 33 installed on the upper surface of the right end of the tank body 1. There is a right water pipe 7 arranged between the third water inlet 33 and the first water outlet 6;

[0054] And four groups of filter elements 9 longitudinally distributed between the guiding inclined plate 11 below and the inner wall of the tank body 1. The filter elements 9 can be set as an externally pullable type according to needs, which is convenient for replacing and cleaning the filter elements 9.

[0055] In this embodiment, preferably, a number of water through holes are provided on the surface of the guiding inclined plate 11 to facilitate the entry of water into the filter element 9 for treatment. A second water outlet 8 communicating with the filter element 9 is provided on the lower surface of the left end of the tank body 1, and a third water outlet 34 communicating with the filter element 9 is provided on the lower surface of the right end of the tank body 1. A left water pipe 10 is provided between the first water outlet 6 and the second water inlet 13 on the left side, and a right water pipe 7 is provided between the first water outlet 6 and the third water inlet 33 on the right side. A valve two 31 is provided on the left water pipe 10, and a valve one 30 is provided on the right water pipe 7. Drain pipes are connected to both the second water outlet 8 and the third water outlet 34, and a valve seven 27 and a valve eight 23 are respectively provided on the two drain pipes. Two branch pipes are respectively connected to the left water pipe 10 and the right water pipe 7, and a valve four 32 and a valve three 25 are respectively provided on the two branch pipes. Connecting water pipes are respectively provided between the two branch pipes and the two drain pipes, and a valve five 26 and a valve six 24 are provided on the two connecting water pipes.

[0056] In this embodiment, preferably, the left filtration zone one further includes a water distribution pipe 19 located above the filter bed 12. The water distribution pipe 19 is connected to the second water inlet 13, and a number of water distribution openings are evenly provided on the surface of the water distribution pipe 19 to facilitate uniform water distribution to the filter bed 12 and facilitate the full filtration treatment of the wastewater by the filter bed 12.

[0057] In summary, for the three methods of oil-water treatment in cooperation with the left filtration zone one, the middle pretreatment zone, and the right filtration zone two, when the filter element 9 in the left filtration zone one is replaced, the right filtration zone two works. The specific working process is that the water flowing out from the lower part of the hydrocyclone 2 enters the wastewater chamber, and then enters the third water inlet 33 of the right filtration zone two through the right water pipe 7 and the valve one 30 connected to the first water outlet 6. After being filtered by the filter material of the right filter bed 12, it flows downward, and the purified water after being filtered by the filter element 9 is transported out through the valve eight 23; when the filter element 9 in the right filtration zone two is replaced, the left filtration zone one works. The specific working process is that the water flowing out from the lower part of the hydrocyclone 2 enters the wastewater chamber, and then enters the second water inlet 13 of the left filtration zone one through the left water pipe 10 and the valve one 30 connected to the first water outlet 6. After being filtered by the filter material of the left filter bed 12, it flows downward, and the purified water after being filtered by the filter element 9 is transported out through the valve seven 27; at this time, continuous treatment of the oily wastewater can be ensured, the trouble of shutting down for replacing the filter element 9 can be avoided, the shutdown cost can be reduced, and the filtration continuity or treatment effect of the oily wastewater can be improved.

[0058] Embodiment Three

[0059] Refer to Figure 5 , which is the third embodiment of the present invention.

[0060] In this embodiment, preferably, a flushing structure 17 for cleaning the filter material in the filter bed 12 is provided inside both the left filtration zone one and the right filtration zone two. The flushing structure 17 includes:

[0061] The scrubbing barrel 21 for cleaning the filter media. The scrubbing barrel 21 cleans the filter media, and a pipeline is connected to the scrubbing barrel 21, and a ninth valve 28 is arranged on the pipeline;

[0062] The cloth-feeding barrel 22 extending above the filter bed 12. The cloth-feeding barrel 22 is in a Y shape, and the cloth outlet at its lower end extends towards both ends of the filter bed 12, facilitating the re-filling of the filter media into the filter bed 12, and the filter media has a large distribution range and will not converge in the middle of the filter bed 12;

[0063] The left electric valve 35 and the right electric valve 36 for controlling the filter media in the scrubbing barrel 21 to enter the cloth-feeding barrel 22;

[0064] And the backwash discharge port 20 installed at the bottom of the tank body 1. The backwash discharge port 20 can introduce cleaning water and filter media into the scrubbing barrel 21, and the backwash discharge port 20 is located between the two guiding inclined plates 11.

[0065] In this embodiment, preferably, the flushing structure 17 further includes a sewage discharge pipe 14 communicating with the inside of the scrubbing barrel 21, facilitating the discharge of sewage.

[0066] In this embodiment, preferably, an oil collection device communicating with the left filter zone one, the middle pretreatment zone, and the right filter zone two respectively is arranged at the top of the tank body 1. An oil-water interface meter 16 is arranged at the top of the oil collection device, and an oil collection pipe 15 is arranged between multiple oil collection devices, and valves are arranged on the oil collection pipes 15 at the tops of multiple oil collection devices.

[0067] In summary, for the four ways of oil-water treatment by the cooperation of the left filter zone one, the middle pretreatment zone, and the right filter zone two, when the filter bed 12 in the left filter zone one is relatively dirty and the filter media needs to be cleaned, the left filter zone one and the right filter zone two work in series. The specific working process is that the water flowing out from the lower part of the hydrocyclone 2 enters the wastewater cavity, and then enters the second water inlet 13 of the left filter zone one through the second valve 31 at the first water outlet 6. After being filtered by the filter media in the left filter bed 12, it flows downward. The filtered water is further filtered by the filter element 9 and then enters the purification cavity. The purified water in the left filter zone one then enters the third water inlet 33 through the fifth valve 26 and the third valve 25. After being filtered by the filter media in the left filter bed 12, it flows downward. The filtered water is further filtered by the filter element 9 and then enters the purification cavity. The purified water is conveyed out through the eighth valve 23; later, the ninth valve 28 is opened, and under the action of water pressure, the filter media in the lower funnel is pressed into the upper scrubbing barrel 21. Under the action of agents such as cleaning agents and bactericides, the filter media is scrubbed, and the sewage is discharged from the ninth valve 28 at the upper part of the scrubbing barrel 21. After the filter media is cleaned, the ninth valve 28 is closed, and the lower electric valve 35 of the scrubbing barrel 21 is opened, and the cloth-feeding barrel 22 falls into the filter bed 12 to complete the filter media cleaning work.

[0068] The five ways of oil-water treatment by the cooperation of the left filtration area I, the middle pretreatment area, and the right filtration area II. When the filter bed 12 in the right filtration area II is dirty and needs to be cleaned, the right filtration area II and the left filtration area I work in series. The specific working process is that the water flowing out from the lower part of the hydrocyclone 2 enters the waste water chamber, and then enters the third water inlet 33 of the right filtration area II through the first water outlet 6 and the valve 30. After being filtered by the filter material in the left filter bed 12, it flows downward. The filtered water is then filtered by the filter element 9 and enters the purification chamber. The purified water in the right filtration area II then enters the second water inlet 13 through the valve 6 and the valve 4. After being filtered by the filter material in the left filter bed 12, it flows downward. The filtered water is then filtered by the filter element 9 and enters the purification chamber. The purified water is transported out through the valve 7. Later, the valve 29 is opened, and the filter material in the lower funnel is pressed into the upper scrubbing barrel 21 under the action of water pressure. Under the action of agents such as cleaning agents and fungicides, the filter material is scrubbed, and the sewage is discharged from the valve 29 at the upper part of the scrubbing barrel 21. After the filter material is cleaned, the valve 29 is closed, and the electric valve 36 at the lower part of the scrubbing barrel 21 is opened, and the cloth barrel 22 falls into the filter bed 12 to complete the filter material cleaning work.

[0069] Embodiment 4

[0070] This embodiment is obtained by combining Embodiment 1, Embodiment 2, and Embodiment 3.

[0071] During use, in order to ensure that the treated water quality index is qualified, the left filtration area I, the middle pretreatment area, and the right filtration area II are made to work together simultaneously. The treatment time of the waste water can be extended and the filtration steps can be increased. Multi-stage filtration improves the treatment effect of the oily waste water. When the amount of the oily waste water is large, the middle pretreatment area is made to work in parallel with the left filtration area I and the right filtration area II to achieve the emergency treatment of the sudden increase in the front-end waste water. When the filter element 9 on either side needs to be replaced, the filter element 9 on the other side continues to work to ensure continuous treatment of the oily waste water, and the situation of shutting down the entire filtration tank for cleaning will not occur, reducing the cost of shutdown and improving the treatment efficiency of the oily waste water.

[0072] The above embodiments are only used to illustrate the technical method of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical method of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical method of the present invention.

Claims

1. A coalescing and filtering tank for treating oily wastewater, characterized in that, Comprising: A tank body (1), the interior of the tank body (1) is sequentially divided into a left filtration zone one, a middle pretreatment zone, and a right filtration zone two from left to right. A first water outlet (6) is provided at the bottom of the middle pretreatment zone; the middle pretreatment zone includes a hydrocyclone (2) vertically installed at the middle position of the tank body (1). Above the hydrocyclone (2), multiple separation inclined plates (5) for oil-water separation are provided. In the hydrocyclone (2), water moves downward and flows out from the lower part of the hydrocyclone (2), while oil flows out from the upper part of the hydrocyclone (2) and is dehydrated through the separation inclined plates (5). The water separated from the middle pretreatment zone enters the left filtration zone one and the right filtration zone two respectively and is filtered by the filter beds (12) provided in the left filtration zone one and the right filtration zone two; the left filtration zone one and the right filtration zone two have the same structure. The left filtration zone one includes: a filter bed (12) horizontally installed inside the tank body (1), a guiding inclined plate (11) provided inside the tank body (1) below the filter bed (12), and a water storage cavity is formed between the lower surface of the guiding inclined plate (11) and the inner wall of the tank body (1); a second water inlet (13) installed on the upper surface of the left end of the tank body (1), and a left water pipe (10) is provided between the second water inlet (13) and the first water outlet (6); a third water inlet (33) installed on the upper surface of the right end of the tank body (1), and a right water pipe (7) is provided between the third water inlet (33) and the first water outlet (6); and four groups of filter elements (9) longitudinally distributed between the guiding inclined plate (11) and the inner wall of the tank body (1). The left filtration zone one further includes a water distribution pipe (19) located above the filter bed (12), the water distribution pipe (19) is connected to the second water inlet (13), and a plurality of water distribution openings are evenly formed on the surface of the water distribution pipe (19). Flushing structures (17) for cleaning the filter media in the filter beds (12) are provided inside both the left filtration zone one and the right filtration zone two. The flushing structures (17) include: a scrubbing barrel (21) for cleaning the filter media; a cloth barrel (22) extending above the filter bed (12), the cloth barrel (22) is in a Y shape, and the cloth outlet at its lower end extends towards both ends of the filter bed (12); a left electric valve one (35) or a right electric valve two (36) for controlling the filter media in the scrubbing barrel (21) to enter the cloth barrel (22); and a backwashing discharge port (20) installed at the bottom of the tank body (1), and the backwashing discharge port (20) feeds cleaning water and filter media into the scrubbing barrel (21), and the backwashing discharge port (20) is located between two guiding inclined plates (11). The flushing structure (17) further includes a sewage discharge pipe (14) communicated with the inside of the scrubbing barrel (21), and a valve nine (28) is provided on the sewage discharge pipe (14).

2. The coalescing filter tank for treating oily wastewater according to claim 1, characterized in that, The middle pretreatment zone further includes a first water inlet (3) provided on the front surface of the tank body (1), and the rear end of the first water inlet (3) is communicated with the hydrocyclone (2) and supplies water to the inside of the hydrocyclone (2).

3. The coalescing filter tank for treating oily wastewater according to claim 2, characterized in that, The middle pretreatment zone further includes a partition plate (4) horizontally installed on the inner wall of the tank body (1) and located at the upper end of the hydrocyclone (2), and a water conveyance hole is formed on the upper surface of the partition plate (4).

4. The coalescing filter tank for treating oily wastewater according to claim 3, characterized in that, A wastewater chamber is formed between the hydrocyclone (2), the partition plate (4) and the inner wall of the tank body (1), and a first water outlet (6) communicating with the water chamber is arranged at the bottom of the tank body (1).

5. The coalescing filter tank for treating oily wastewater according to claim 4, characterized in that, A plurality of water passing holes are formed on the surface of the guiding inclined plate (11), and a second water outlet (8) communicating with the filter element (9) is arranged on the lower surface of the left end of the tank body (1); a third water outlet (34) communicating with the filter element (9) is arranged on the lower surface of the right end of the tank body (1).

6. The coalescing filter tank for treating oily wastewater according to claim 1, characterized in that, An oil collecting device communicating with the left filtering area I, the middle pretreatment area and the right filtering area II respectively is arranged at the top of the tank body (1). An oil-water interface detector (16) is arranged at the top of the oil collecting device, and an oil collecting pipe (15) is arranged between a plurality of oil collecting devices.

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