Air floatation and extraction coupled oil removal device and method

Abstract

The invention provides an air floatation and extraction coupled oil removal device. The device is divided into an air floatation enhanced coalescence unit and an extraction unit, the air flotation reinforced coalescence unit is provided with an inner cylinder, a first-stage coalescence layer is arranged outside the inner cylinder, and a second-stage coalescence layer is arranged in the inner cylinder; the extraction unit is provided with a mixing separator and a coalescer from top to bottom; the device integrates a jet mixing function and a static mixing function. The invention also provides an air floatation and extraction coupled oil removal method adopting the device, the method comprises the following steps: sequentially carrying out air floatation, coalescence, extraction and other process treatments on the oil-containing wastewater, combining the advantages of various treatment processes, realizing air floatation and fiber coupling, efficient extraction and separation, and improving the oil removal efficiency of the wastewater.

Description

Technical Field

[0001] The present invention belongs to the technical field of heterogeneous phase separation, and specifically relates to an air flotation extraction coupled oil removal device and method. Specifically, the device is used to perform air flotation coupled coalescence, jet mixing, extraction and other process treatments on oily wastewater to achieve separation of the oil phase in the oily wastewater. Background Art

[0002] In recent years, water pollution has become an important factor restricting industrial development. Among them, oily wastewater generated by the petrochemical industry accounts for a large proportion of my country's industrial wastewater. Therefore, how to efficiently treat oily wastewater is one of the important tasks of environmental protection in my country. At present, there are many oil removal devices and methods, but these devices have different advantages and disadvantages, and have problems such as low working efficiency, high manufacturing cost, and secondary pollution. In view of this, it is necessary to study a new oily wastewater oil removal device and method.

[0003] Chinese patent CN216837238U discloses a complete set of sewage classification, coalescence and oil removal equipment, including a pretreatment device, a light and heavy oil separation device and a heavy oil deep separation device; wherein the pretreatment device includes a pretreatment tank, the upper and lower ends of which are respectively provided with a first light oil bag and a first heavy oil bag, and a packing column module is provided inside; the interior of the light and heavy oil separation tank is provided with a first distributor, a first coalescence module and a first sedimentation module from left to right; the interior of the deep separation tank is provided with a second distributor, a second coalescence module and a second sedimentation module from left to right. Although this device can deal with the problem of light / heavy oil at the same time, it has the problem of low light oil treatment efficiency, and its structure is relatively complex and the manufacturing cost is high.

[0004] Chinese patent CN112919571A discloses a device and method for flotation-enhanced multi-stage fiber coalescence oil removal, which first physically demulsifies the emulsion; the demulsified fluid enters the oleophilic fiber coalescence layer, so that tiny oil droplets are wetted and coalesced in the coalescence layer; the oil phase in the coalescence layer moves upward under the drive of buoyancy and bubbles, and the small oil droplets further coalesce and grow under the drive of bubbles, and are discharged through the first oil phase discharge port, and other oil phases enter the drainage layer; relying on the capillary repulsion of the oleophobic fiber drainage layer, the front end of the drainage layer can capture the oil phase droplets, and the coalesced oil droplets are more likely to move to the upper end of the drainage layer under the action of buoyancy and bubbles, promoting the oil phase to flow out through the second oil phase discharge port. Although the method and device of this invention can achieve deep demulsification, coalescence and separation of oily wastewater, and achieve efficient and clean treatment of oily wastewater. However, due to the complexity of its internal coalescence layer, the manufacturing cost may increase. And because the device is a highly integrated tank, it can effectively remove oil from different wastewaters when dealing with complex industrial wastewater.

[0005] Therefore, there is an urgent need in the art to develop an oil removal device that can not only deeply treat oily wastewater and remove oil efficiently, but also cope with different wastewater conditions and replace internal components to achieve the best effect. Summary of the invention

[0006] In order to solve the problems and shortcomings of the prior art, the inventors have found after extensive and in-depth research that adding flotation to the coalescence process can accelerate the floating rate of oil droplets, thereby increasing the collision between the oil droplets and the fibers in the coalescence layer and strengthening the coalescence oil removal effect. At the same time, the present invention adopts multi-stage processing, coupling the extraction technology in coalescence, realizing the continuous process of flotation-coagulation coupling, extraction, and separation, and solving the problem of low oil removal efficiency of a single process. At the same time, a new type of high-efficiency mixing separator is designed in the extraction process. The mixer integrates the functions of injection, static mixing, and rectification, which can accelerate the mixing of the extractant and the oily wastewater, thereby improving the extraction efficiency and achieving deep purification of oil-water separation. Based on the above concepts and discoveries, the present invention has been completed.

[0007] The present invention first provides an oil removal device coupled with air flotation extraction, the device comprising:

[0008] An oil removal tank body, and an air flotation enhanced coalescence unit and an extraction unit sequentially arranged from top to bottom in the oil removal tank body, wherein the air flotation enhanced coalescence unit and the extraction unit are separated by a unit partition;

[0009] The air flotation enhanced coalescence unit is provided with an inner cylinder, an oily wastewater inlet and a micro-nano bubble inlet are provided at the bottom, a primary coalescence layer and a secondary coalescence layer are provided in the middle, and an oil phase outlet and an exhaust port are provided at the top;

[0010] The extraction unit is provided with an extractant inlet at the top, an extractant outlet in the middle, a coalescing layer at the bottom, a treated wastewater outlet at the bottom, and a mixing separator, which is fixed in the oil removal tank body by a partition, and the partition divides the extraction unit into two closed spaces;

[0011] The inner cylinder of the air flotation enhanced coalescence unit is connected to the mixing separator of the extraction unit through a pipeline and a plurality of nozzles at its lower end.

[0012] In the air flotation enhanced agglomeration unit, the primary agglomeration layer is located outside the inner cylinder, is made of a mixed stainless steel wire fiber mesh, and is composed of oleophilic fibers and stainless steel wires. The diameter of the oleophilic fibers is 10-30 μm, and the porosity is 0.75-0.95; the secondary agglomeration layer is located inside the inner cylinder, and is composed of oleophobic fibers and stainless steel wires. The diameter of the oleophobic fibers is 10-50 μm, and the diameter of the stainless steel wire is 200-300 μm.

[0013] In the extraction unit, the mixing separator is provided with an axial mainstream inlet and a tangential secondary inlet, the axial mainstream inlet is connected to the nozzle; the mixing separator is provided with an intake chamber at the nozzle outlet, the intake chamber is connected to the mixing chamber; the mixing chamber is connected to the diffusion chamber.

[0014] In the extraction unit, the mixing chamber components of the mixing separator are replaceable, which are one or more combinations of traditional static mixer internal components SX, SV, SH, SL, SK and SD, or one or more combinations of new mixing components I, II and III.

[0015] In the extraction unit, the diffusion chamber of the mixing separator is connected to a cylindrical rectifier with small holes on the side, and the diameter of the small holes is 1 mm.

[0016] In the extraction unit, the novel mixing component I is composed of a plurality of groups of baffles with holes, the number of holes of the baffles with holes is 16-20, the hole diameter is 1-2 mm, and adjacent baffles are arranged to be 15°-45° apart.

[0017] In the extraction unit, the novel mixing component II is composed of multiple groups of perforated baffles, which are divided into two types: inner perforated baffles and outer perforated baffles. Both types of baffles have 8 holes and a hole diameter of 1-2 mm. Different types of baffles are arranged at intervals.

[0018] In the extraction unit, the novel mixing component III is composed of inner and outer plates. The outer plate is a circular plate with inner and outer diameters of 10 mm and 20 mm respectively; the inner plate is a circular plate with a diameter of 12 mm; the inner and outer plates are connected by 4 support rods.

[0019] In the extraction unit, the coalescence layer is formed by mixing oleophilic fibers with a roughness Ra of 0.6-0.9 μm and stainless steel wires, and has a thickness of 100-300 mm.

[0020] Secondly, the present invention also provides an oil removal method coupled with air flotation extraction, which comprises the following steps:

[0021] (a) The oily wastewater to be treated enters the outer cylinder through the wastewater inlet, and first floats with the bubbles entering from the micro-nano bubble inlet. The oil droplets in the wastewater come into contact with the bubbles. Under the action of the bubbles, the oil droplets accelerate to rise through the primary coalescing layer. Under the coupling action of the micro-nano bubbles and the primary coalescing layer, the oil droplets continue to coalesce and grow on the oleophilic fibers, and finally suspend to the top of the tank body and are discharged from the oil phase outlet;

[0022] (b) the wastewater treated in step (a) enters the inner cylinder and flows downward through the secondary coalescing layer, and the oil droplets are retained in the upper part because they cannot pass through the oleophobic layer;

[0023] (c) the wastewater treated in step (b) flows into the mixing separator through the axial main flow inlet, and is sprayed and mixed with the extractant flowing in from the tangential secondary flow inlet. The two-phase fluid is intensively mixed through the mixing chamber component, and finally flows to the lower part of the tank through the rectifier;

[0024] (d) The wastewater containing the extractant after treatment in step (c) passes through the coalescence layer, and the extractant droplets are coalesced and suspended in the upper layer at the lower part of the tank body, and flow out through the extractant outlet, and the aqueous phase after extraction flows out through the wastewater outlet.

[0025] Wherein: in step (a), the oil concentration in the oily wastewater is not more than 1500 mg / L, and the superficial flow rate of the fluid in the device is 0.02-0.04 m / s. In step (c), the extractant is one or any combination of cyclohexane, kerosene or toluene, the extraction temperature is 20-30°C, and the extraction ratio O / A=(1-2):1.

[0026] The beneficial effects of the present invention are:

[0027] (1) The air flotation coupled coalescence process is adopted. Micro-nano bubbles can accelerate the floating of oil droplets during the floating process, achieving the effect of air flotation oil removal; and can also strengthen the collision between oil droplets and fibers, producing a better coalescence effect. In addition, the air flotation enhanced coalescence unit adopts an inner and outer cylinder design to achieve multi-stage coalescence. After the first coalescence layer, the small oil droplets remaining in the water phase are blocked by the oleophobic fibers inside the second coalescence layer, further improving the coalescence ability.

[0028] (2) For the extremely small oil droplets remaining in the wastewater that cannot be removed by flotation and agglomeration, an extraction process is adopted. The entire extraction process is completed in a high-efficiency mixing separator. The mixing part of the high-efficiency mixing separator uses detachable components, which can be combined in different ways according to actual needs to achieve the best effect.

[0029] (3) In the post-extraction separation process, in addition to using the traditional gravity sedimentation method to separate the extract phase and the raffinate phase, agglomeration separation technology is added to overcome the shortcomings of low efficiency of traditional gravity sedimentation and improve the separation efficiency of the two phases. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 . Schematic diagram of oil removal device coupled with flotation extraction

[0031] Figure 2 . Schematic diagram of the cross section of the mixing separator in the oil removal device coupled with air flotation extraction

[0032] Figure 3 . Mixing chamber components of the mixing separator

[0033] The reference numerals represent the following equipment and internal parts:

[0034] 1 oil removal tank body; 1-1 air flotation enhanced coalescence unit; 1-2 extraction unit; 2 oily wastewater inlet; 3 micro-nano bubble inlet; 4 primary coalescence layer; 5 secondary coalescence layer; 6 oil phase outlet; 7 exhaust port; 8 extractant inlet; 9 extractant outlet; 10 coalescence layer; 11 treated wastewater outlet; 12 mixing separator; 12-1 suction chamber; 12-2 mixing chamber; 12-3 diffusion chamber; 12-4 cylindrical rectifier; 12-5 axial mainstream inlet; 12-6 tangential secondary inlet; 13 inner cylinder; 14 partition; 15 pipeline; 16 nozzle; 17 unit partition. DETAILED DESCRIPTION

[0035] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0036] Figure 1 This is a schematic diagram of an air flotation extraction coupled oil removal device according to a preferred embodiment of the present invention. It includes an oil removal tank body 1; and an air flotation enhanced coalescence unit 1-1 and an extraction unit 1-2 arranged in sequence from top to bottom in the oil removal tank body; the air flotation enhanced coalescence unit 1-1 and the extraction unit 1-2 are separated by a unit partition 17; the air flotation enhanced coalescence unit 1-1 is provided with an inner cylinder 13, an oily wastewater inlet 2 and a micro-nano bubble inlet 3 at the bottom; a primary coalescence layer 4 and a secondary coalescence layer 5 in the middle; an oil phase outlet 6 and an exhaust port 7 at the top. The extraction unit 1-2 has an extractant inlet 8 at the top, an extractant outlet 9 in the middle, a coalescence layer 10 at the bottom, and a treated wastewater outlet 11 at the bottom, and contains a mixing separator 12 inside, which is fixed in the oil removal tank body by a partition 14, and the partition 14 divides the extraction unit into two closed spaces. The inner cylinder 13 of the air flotation enhanced coalescence unit 1-1 is connected to the mixing separator 12 of the extraction unit 1-2 through a pipeline 15 and multiple nozzles 16 at its lower end. The high-efficiency mixing separator is provided with an axial main flow inlet 12-5 and a tangential secondary flow inlet 12-6, and the high-efficiency mixing separator is provided with an intake chamber 12-1, which is connected to the mixing chamber 12-2; the mixing chamber is connected to the diffusion chamber 12-3. The diffusion chamber is connected to a cylindrical rectifier 12-4 with small holes on the side.

[0037] Oily wastewater with an oil concentration of no more than 1500 mg / L enters the outer cylinder of the flotation enhanced coalescence unit through the wastewater inlet, and first floats with the bubbles entering from the micro-nano bubble inlet. The oil droplets in the wastewater come into contact with the bubbles. Under the action of the bubbles, the oil droplets accelerate to rise through the primary coalescence layer. Under the coupling of the micro-nano bubbles and the inclined plate, the oil droplets continue to coalesce and grow on the oleophilic fibers, and finally suspend to the top of the tank body; the wastewater treated by the primary coalescence layer enters the inner cylinder and flows downward through the secondary coalescence layer. At this time, the small oil droplets remaining in the wastewater are retained at the top of the tank body because they cannot pass through the oleophobic fibers in the secondary coalescence layer, and are finally discharged from the oil phase outlet. The wastewater treated by the flotation enhanced coalescence unit enters the extraction unit through the pipeline. Wastewater flows into the high-efficiency mixing separator through the axial mainstream inlet, and is sprayed and mixed with the extractant flowing in from the tangential secondary flow inlet. The two-phase fluid is intensively mixed through the mixing chamber components. In this process, the extractant fully extracts the oil in the wastewater. Finally, the oil-containing extractant and wastewater flow to the lower part of the tank through the rectifier; the two-phase fluid passes through the coalescence layer, and the extractant droplets are aggregated and suspended in the upper layer of the lower part of the tank, and flow out through the extractant outlet, and the extracted water phase flows out through the wastewater outlet.

[0038] The present invention will be further described below in conjunction with specific examples. However, it should be understood that these examples are only used to illustrate the present invention and do not constitute a limitation of the scope of the present invention. The test methods in the following examples that do not specify specific conditions are usually based on conventional conditions or the conditions recommended by the manufacturer. Unless otherwise stated, all percentages and parts are by weight.

[0039] Embodiment 1:

[0040] In this embodiment, the oily wastewater to be separated comes from the laboratory's homemade oily wastewater. In the primary coalescence layer, the diameter of the oleophilic fiber is 10 μm and its porosity is 0.75. In the secondary coalescence layer, the diameter of the oleophobic fiber is 10 μm, and the diameter of the stainless steel wire is 200 μm. In the experiment, isooctane and tap water are transported to the emulsification kettle in proportion according to the standard of 1500 mg / L, and the emulsification kettle is continuously stirred at a speed of 1000 rpm for 45 minutes to obtain oily wastewater with uniform droplet size distribution and uniform concentration.

[0041] Oily wastewater flows in from the wastewater inlet at a speed of 1000ml / min through a peristaltic pump, micro-nano bubbles flow in from the bubble inlet, with a controlled diameter of 0.5-1μm, and extractant kerosene flows in from the extractant inlet at a speed of 500ml / min. The high-efficiency mixing separator uses type I mixing components, with 20 holes on the perforated baffles, a hole diameter of 1mm, and adjacent baffles are set to be 15° apart.

[0042] According to the national environmental protection standard HJ 637 2012, an infrared spectrophotometer is used to measure the oil concentration in the water to ensure that the oil concentration at the wastewater inlet is 1500 mg / L.

[0043] After treatment, the oil phase flows out through the wastewater outlet. The oil concentration is measured to be lower than 20 mg / L, and the oil removal efficiency reaches 98.26%, meeting the relevant discharge standards for wastewater in my country.

[0044] Embodiment 2:

[0045] The method and device of the present invention were used in a wastewater treatment test at a petrochemical company in Shanghai. The wastewater had low biodegradability, BOD5 / CODCr<0.2, and an oil concentration of 1000-1500 mg / L.

[0046] Oily wastewater flows in from the wastewater inlet at a speed of 1200ml / min through a peristaltic pump, micro-nano bubbles flow in from the bubble inlet, with a controlled diameter of 0.5-1μm, and extractant kerosene flows in from the extractant inlet at a speed of 600ml / min. The high-efficiency mixing separator uses type III mixing components, with inner and outer diameters of the outer plate of 10mm and 20mm respectively; the inner plate diameter is 12mm.

[0047] According to the national environmental protection standard HJ 637 2012, the oil concentration in water is measured using an infrared spectrophotometer. According to the national standard GB11914-89, the CODCr is measured using a Hach DR3900 visible spectrophotometer. According to the HJ505-2009 standard, II BOD analyzer is used to measure CODCr.

[0048] After treatment, the oil phase flows out through the wastewater outlet. The oil concentration is measured to be less than 20mg / L, and the oil removal efficiency is 98.37%, which meets the relevant discharge standards of sewage in my country. At the same time, BOD5 / CODCr>0.3, which improves the biodegradability of wastewater.

[0049] Embodiment 3-12:

[0050] The experimental steps of Examples 3-12 are the same as those of Example 1, but the value ranges of relevant parameters are different, see Table 1 for details.

[0051] Table 1: Ranges of experimental parameters for each embodiment

[0052]

[0053]

[0054] The experimental results of Examples 1-12 are shown in Table 2. As can be seen from Table 2, a higher oil removal efficiency can be achieved by using the method used in the present invention.

[0055] Table 2 Experimental results of various embodiments

[0056] Example Oil concentration Oil removal efficiency (%) 1 Less than 20mg / L 98.26 2 Less than 20mg / L 98.37 3 Less than 20mg / L 98.11 4 Less than 20mg / L 98.16 5 Less than 20mg / L 98.28 6 Less than 20mg / L 98.32 7 Less than 20mg / L 98.25 8 Less than 20mg / L 98.34 9 Less than 20mg / L 98.15 10 Less than 20mg / L 98.37 11 Less than 20mg / L 98.18 12 Less than 20mg / L 98.27

[0057] Finally, it should be noted that the above is only a preferred embodiment of the present invention and does not limit it. Although this patent is described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions recorded in the aforementioned embodiments or to replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included in the protection scope of the present invention.

Claims

1. An air flotation extraction coupled oil removal device, characterized in that: The device comprises: An oil removal tank body (1), and an air flotation enhanced coalescence unit (1-1) and an extraction unit (1-2) arranged in sequence from top to bottom in the oil removal tank body, wherein the air flotation enhanced coalescence unit (1-1) and the extraction unit (1-2) are separated by a unit partition (17); The air flotation enhanced coalescence unit (1-1) is provided with an inner cylinder (13), an oily wastewater inlet (2) and a micro-nano bubble inlet (3) at the bottom, a primary coalescence layer (4) and a secondary coalescence layer (5) at the middle, and an oil phase outlet (6) and an exhaust port (7) at the top; The extraction unit (1-2) is provided with an extractant inlet (8) at the top, an extractant outlet (9) at the middle, a coalescing layer (10) at the bottom, a treated wastewater outlet (11) at the bottom, and a mixing separator (12), which is fixed in the deoiling tank (1) via a partition (14); the partition (14) divides the extraction unit into two closed spaces; The inner cylinder (13) of the air flotation enhanced coalescence unit (1-1) is connected to the mixing separator (12) of the extraction unit (1-2) via a pipeline (15) and a plurality of nozzles (16) at its lower end.

2. The oil removal device according to claim 1, characterized in that: In the air flotation enhanced agglomeration unit (1-1), the primary agglomeration layer (4) is located outside the inner tube (13), is made of a mixed stainless steel wire fiber mesh, and is composed of oleophilic fibers and stainless steel wires. The diameter of the oleophilic fibers is 10-30 μm, and the porosity is 0.75-0.95; the secondary agglomeration layer (5) is located inside the inner tube (13), and is composed of oleophobic fibers and stainless steel wires. The diameter of the oleophobic fibers is 10-50 μm, and the diameter of the stainless steel wire is 200-300 μm.

3. The oil removal device according to claim 1, characterized in that: In the extraction unit (1-2), the mixing separator (12) is provided with an axial main flow inlet (12-5) and a tangential secondary flow inlet (12-6), and the axial main flow inlet (12-5) is connected to the nozzle (16); the mixing separator (12) is provided with an intake chamber (12-1) at the outlet of the nozzle (16), and the intake chamber (12-1) is connected to the mixing chamber (12-2); and the mixing chamber (12-2) is connected to the diffusion chamber (12-3).

4. The oil removal device according to claim 3, characterized in that: In the extraction unit (1-2), the mixing chamber components of the mixing separator (12) are replaceable, and are one or more combinations of traditional static mixer internal components of SX type, SV type, SH type, SL type, SK type and SD type, or one or more combinations of new mixing components of type I, II and III.

5. The oil removal device according to claim 3, characterized in that: In the extraction unit (1-2), the diffusion chamber (12-3) of the mixing separator (12) is connected below to a cylindrical rectifier (12-4) with small holes on the side, and the diameter of the small holes is 1 mm.

6. The oil removal device according to claim 4, characterized in that: In the extraction unit (1-2), the novel mixing component I is composed of a plurality of groups of perforated baffles, the number of holes in the perforated baffles is 16-20, the hole diameter is 1-2 mm, and adjacent baffles are arranged to be 15°-45° apart.

7. The oil removal device according to claim 4, characterized in that: In the extraction unit (1-2), the novel mixing component II is composed of multiple groups of perforated baffles, which are divided into two types: inner perforated baffles and outer perforated baffles. Both types of baffles have 8 holes and a hole diameter of 1-2 mm. Different types of baffles are arranged at intervals.

8. The oil removal device according to claim 4, characterized in that: In the extraction unit (1-2), the novel mixing component III is composed of inner and outer plates, the outer plate is a circular plate with inner and outer diameters of 10 mm and 20 mm respectively; the inner plate is a circular plate with a diameter of 12 mm; the inner and outer plates are connected by 4 support rods.

9. The oil removal device according to claim 1, characterized in that: In the extraction unit (1-2), the coalescing layer (10) is made of a mixture of oleophilic fibers with a roughness Ra of 0.6-0.9 μm and stainless steel wires, and has a thickness of 100-300 mm.

10. An air flotation extraction coupled oil removal method using the oil removal device of claim 1, characterized in that: The method comprises the following steps: (a) The oily wastewater to be treated enters the outer cylinder through the wastewater inlet (2), and first floats with the bubbles entering from the micro-nano bubble inlet (3). The oil droplets in the wastewater come into contact with the bubbles. Under the action of the bubbles, the oil droplets are accelerated to rise through the primary coalescing layer (4). Under the coupling action of the micro-nano bubbles and the primary coalescing layer (4), the oil droplets continue to coalesce and grow on the oleophilic fibers, and finally suspend to the top of the tank body and are discharged from the oil phase outlet (6); (b) the wastewater treated in step (a) enters the inner cylinder (13), flows downward through the secondary coalescing layer (5), and the oil droplets are retained in the upper part because they cannot pass through the oleophobic layer; (c) the wastewater treated in step (b) flows into the mixing separator (12) through the axial main flow inlet (12-5), and is sprayed and mixed with the extractant flowing in from the tangential secondary flow inlet (12-6), and the two-phase fluid is intensively mixed through the mixing chamber component, and finally flows to the lower part of the tank through the rectifier (12-4); (d) The wastewater containing the extractant after treatment in step (c) passes through the coalescing layer (10), and the extractant droplets are coalesced and suspended in the upper layer at the lower part of the tank body, and flow out through the extractant outlet (9), and the aqueous phase after extraction flows out through the wastewater outlet (11).

11. The oil removal method according to claim 10, characterized in that: In step (a), the oil concentration in the oily wastewater is not greater than 1500 mg / L, and the superficial flow velocity of the fluid in the device is 0.02-0.04 m / s.

12. The oil removal method according to claim 10, characterized in that: In step (c), the extractant is one or any combination of cyclohexane, kerosene or toluene, the extraction temperature is 20-30° C., and the extraction phase ratio O / A=(1-2):1.

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