A device and method for removing oil from waste lye by extraction coupled with horizontal flow coalescence filtration

Abstract

The application relates to a device and a method for removing oil from waste alkali liquor by extraction coupling horizontal flow sand coalescence filtration, which comprises a micro-extraction chaotic reinforced mixing module, a first flow sand fine particle coalescence filtration module, a second flow sand coarse particle coalescence filtration module, a fiber coalescence module and a horizontal tank body. The device adopts liquid drop micro-dispersion and chaotic flow reinforced mixing to improve the butter extraction efficiency. After the mixing liquid is subjected to the coalescence and demulsification of the oil / water particles and fibers in the first flow sand fine particle coalescence filtration module and the second flow sand coarse particle coalescence filtration module, the oil-water two-phase separation is completed in the clarification zone. The suspended matters in the mixing liquid are intercepted in the particle pores. The system is provided with an intermittent self-control valve to adjust the vapor bubble controller to release the vapor bubbles to make the flow sand particles be on-line fluidized and cleaned. The impurities are floated and collected on the top of the fluidized expansion package and are discharged regularly. The application integrates the effective removal of dissolved oil, non-dissolved oil and suspended matters, and is especially suitable for the treatment of complex waste water containing high-viscosity oil.

Description

TECHNICAL FIELD

[0001] The application relates to a device and a method for removing oil from waste lye by extraction coupling horizontal flow coalescence filtration, in particular to a device and a method for removing oil from waste lye without interruption by integrating the effective removal of dissolved oil, non-dissolved oil and suspended matter. BACKGROUND

[0002] In the process of catalytic cracking, hydrocracking, hydrofining, delayed coking and the like in the field of petroleum and coal chemical industry, sulfides in raw oil are cracked or react with hydrogen to generate hydrogen sulfide and other acid gases in a high-temperature and high-pressure environment, and then the acid gases in light hydrocarbons are removed by alkali washing. The alkali washing process brings a large amount of waste lye, and the yellow oil in the waste lye is mainly a polymer after cross-linking polymerization of unsaturated hydrocarbons and condensation of aldehydes and ketones, with a concentration of 2%-10% and a high emulsification degree, existing in the form of floating, suspending and adhering to the surface of solids. Unlike conventional oil products, the yellow oil has a large viscosity and is prone to coking at low temperature; the waste lye also contains dissolved oil brought by the washing of light hydrocarbons, and the complex characteristics of the oil pollutants in multiple forms increase the difficulty of treatment. At present, most waste lye treatment facilities usually have a small tower diameter and are provided with fillers, and problems such as pipeline blockage and failure of treatment devices to normally operate occur during the transportation or treatment of waste lye, resulting in shutdown for maintenance. Therefore, it is of great significance to add effective yellow oil removal equipment to the waste lye treatment process for the recycling and resourceization of waste lye.

[0003] CN202072510U discloses a device for removing yellow oil from waste lye. The device mixes aromatic gasoline and waste lye filtered by a filter through a mixer, and then realizes oil-water separation through two coalescers, so as to realize the extraction of yellow oil from waste lye by gasoline according to the mutual solubility of oil. Although the device can remove yellow oil, it needs to be combined with multiple devices, occupies a large space, needs to introduce a filter to filter and intercept solid impurities such as suspended matter, and needs to be parked for cleaning after long-term use.

[0004] CN107673452A discloses a method for treating waste lye from ethylene cracking. The method mixes waste lye and a detergent (gasoline or toluene) through a mixer, and then realizes oil-alkali separation in a common coalescer at 20-60 DEG C for 1-5 h. Although the method can remove yellow oil, it needs to use more devices, occupies a large area, and needs to be placed for a long time, which seriously restricts the treatment efficiency of waste lye and is low in economy.

[0005] The generated amount of butter in waste lye fluctuates greatly, and the content of impurities such as iron filings, butter particles and suspended matters is high. By using conventional extraction, membrane treatment, adsorption filtration, conventional coalescence filtration and the like, there are defects such as easy blockage, difficult cleaning, difficult and incomplete oil-water separation of emulsion after extraction. Compared with the traditional treatment method, the present application adopts a horizontal design and a new treatment method of extraction coupled with horizontal flow sand coalescence filtration, which can realize online self-cleaning of the equipment while effectively removing oil with high precision, and has the advantages of simple operation, energy saving and consumption reduction. SUMMARY

[0006] In view of the problems and defects of the prior art and equipment, based on chaotic flow reinforced mixing extraction, fluidization characteristics of hydrophilic and hydrophobic flow sand particles and reinforced oil-water coalescence separation function, and in combination with hydrophilic and hydrophobic fiber reinforced demulsification coalescence performance, the present application provides a waste lye oil removal method and device of extraction coupled with horizontal flow sand coalescence filtration.

[0007] The technical scheme adopted by the present application is as follows:

[0008] An oil removal device for waste lye by extraction coupled with horizontal flow sand coalescence filtration, characterized in that the device comprises a horizontal tank body, a micro-extraction chaotic reinforced mixing module, a first flow sand fine particle coalescence filtration module, a second flow sand coarse particle coalescence filtration module, a fiber coalescence module and a process pump for circulating extractant.

[0009] The micro-extraction chaotic reinforced mixing module comprises a mixing chamber provided with a flow resistance block outside the front end of the horizontal tank body and connected with an asymmetric mixing flow channel in the front part of the horizontal tank body, a waste lye inlet on the side surface of the mixing chamber and a liquid droplet dispersion nozzle connected with the extractant circulating pump at the bottom.

[0010] The first flow sand fine particle coalescence filtration module and the second flow sand coarse particle coalescence filtration module are sequentially located in the middle part of the horizontal tank body and comprise two flow expansion bags above the horizontal tank body, a blowdown port provided at the top of each flow expansion bag, a particle grid provided at the top of the flow chamber, a particle bed layer below the particle grid, liquid distributors provided at both sides of the particle bed layer and a vapor bubble controller provided at the bottom.

[0011] The fiber coalescence module is located at the clarification zone behind the second flow sand coarse particle coalescence filtration module and is a woven bed composed of hydrophilic fibers and hydrophobic fibers.

[0012] Preferably, the small particle size lipophilic, hydrophilic particles have a particle size of 0.25-1mm, the stacking ratio of the lipophilic and hydrophilic particles is (1:3)-(3:1), the contact angle of the lipophilic particles in water with oil is not more than 70°, and the porosity is 20%-50%; the large particle size lipophilic, hydrophilic particles have a particle size of 0.5-3mm, the stacking ratio of the lipophilic and hydrophilic particles is (1:3)-(3:1), the contact angle of the lipophilic particles in water with oil is not more than 70°, and the porosity is 60%-90%.

[0013] Preferably, the inner diameter of the droplet dispersion nozzle is 0.5-4mm, the flow resistance block adopts 6 diamond-shaped metal blocks, and the asymmetric annular flow channel is 3 groups.

[0014] Preferably, the horizontal tank body is provided with a head on both sides, the radius is D, the length is L, D is 10%-20% of L; the horizontal length of the primary flow sand fine particle coalescence filtration module and the secondary flow sand coarse particle coalescence filtration module is L1, L1 is 1.5-3 times of D; the cross-sectional radius d1 of the two upper cylindrical fluidized expansion bags is 25%-50% of L1, and the height h1 is 0.8-1 times of D; a water phase outlet is arranged below the tail part of the horizontal tank body, an oil discharge outlet is arranged at the top of the cylindrical oil bag, the cross-sectional radius d2 of the cylindrical oil bag is 30%-60% of D, and the height h2 is 0.5-0.8 times of D; flanges are arranged on the outer connection ports of the horizontal tank body.

[0015] Preferably, when the cylinder diameter of the horizontal tank body is between 0.2-0.5m, the particle bed height in the primary flow sand fine particle coalescence filtration module and the secondary flow sand coarse particle coalescence filtration module is 0.3-0.8m; when the cylinder diameter is between 1-2m, the particle bed height in the primary flow sand fine particle coalescence filtration module and the secondary flow sand coarse particle coalescence filtration module is 1.5-3.5m.

[0016] Preferably, in the fiber coalescence module, the hydrophilic fiber is preferably metal fiber 316L, and the hydrophobic fiber is preferably polytetrafluoroethylene.

[0017] The application also provides a waste alkali liquid oil removal method by extraction coupled horizontal flow sand coalescence filtration, characterized in that the method comprises the following steps:

[0018] (1): The high-viscosity butter-containing waste alkali liquid from the liquid storage pool or the alkali washing tower enters the micro-extraction chaotic enhanced mixing module through the alkali liquid inlet, the extractant is pressurized by the extractant circulating pump to the droplet dispersion nozzle, and small particle size microdroplets are dispersed into the waste alkali liquid and enter the asymmetric annular flow channel with the waste alkali liquid, the ratio of the extractant to the waste alkali liquid is 1:10-1:1, and the alkali liquid-extractant mixed liquid containing oil-in-water and water-in-oil droplets is fully mixed and extracted and then enters the buffer zone.

[0019] (2): The above-mentioned mixed solution enters the first level of flow sand fine particle coalescence filter module, flows into the particle bed layer of the first level of flow sand fine particle coalescence filter module through a liquid distributor, and the filtration of solid particles and suspended impurities is completed by using the front half small particle size particle microchannel, so that the butter particles and the suspended matter are filtered and intercepted, and the oil / water droplets are captured and coalesced on the lipophilic / hydrophobic particle surface to realize preliminary two-phase separation;

[0020] (3): The liquid distributor flows to the particle bed layer of the second level of flow sand coarse particle coalescence filter module, and deep coalescence separation of large droplets which have grown and not yet completed separation is realized.

[0021] (4): The hydrophilic and hydrophobic fiber module located in the clarification zone completes the capture, demulsification and coalescence of small particle size droplets, the butter-containing extractant is discharged from the top oil outlet to the extractant recovery process area for next step processing, the waste alkali solution from which butter is removed is discharged from the bottom water phase outlet to the waste alkali solution recovery process area for alkali recovery and utilization; at the same time, in view of the high concentration of suspended matter and viscous butter in the waste alkali solution, the system is provided with an intermittent on-off valve to adjust a steam bubble controller to release steam bubbles, so that the flow sand particles are fluffy in the fluidized expansion bag, the porosity of the particles is expanded, and the flow sand particle module is continuously and on-line self-cleaned under the impact of the coming liquid and the steam bubble explosion impact, and the impurities are floated and collected on the top of the fluidized expansion bag and are regularly discharged.

[0022] In the step (1), the content of dispersed oil and emulsified oil in the waste alkali solution entering the micro-extraction chaotic enhanced mixing module is less than or equal to 10%, the content of dissolved oil is less than or equal to 2%, and the extractant is derived from one or more of process raw materials or process products (crude gasoline, benzene series, etc.).

[0023] In the step (1), the dispersed microdroplets entering the mixing cavity through the droplet dispersion nozzle have a particle size of 20-100 μm, a spraying pressure difference of 0.2-0.4 MPa, a nozzle diameter of 0.5-4 mm, an average flow velocity of the asymmetric annular flow channel of 0.5-5 m / s, and a turbulent intensity of 10%-20%.

[0024] In the step (2), the fluidization period of the second level of flow sand coarse particle coalescence filter module is more than five times that of the first level of flow sand fine particle coalescence filter module, and the horizontal cross-sectional flow velocity in the module is 0.005-0.1 m / s.

[0025] In the step (4), the fluidization steam is low-pressure steam at 120 ℃, and its dosage is 1-20 times the water flow rate according to the water quality of the treated waste alkali solution, the first level of flow sand fluidization period is 48-72 h, and the single fluidization time is 10 min.

[0026] The present application has the following beneficial effects:

[0027] 1. The application provides a non-stop extraction coupled horizontal flow sand coalescence filtration waste lye oil removal method and device, the extraction coupled horizontal flow sand coalescence filtration waste lye oil removal device includes a micro-mixing chaotic reinforcement module, a first flow sand fine particle coalescence filtration module, a second flow sand coarse particle coalescence filtration module and a fiber coalescence module; the micro-mixing chaotic reinforcement module realizes dispersion of extraction agent droplets into waste lye through internal nozzles, then uses flow resistance block collision and asymmetric flow channel to strengthen mixing and improve extraction effect; then a first flow sand fine particle coalescence filtration bed layer is used to remove suspended solids and preliminarily coalesce and grow oil droplets, then a second flow sand coarse particle coalescence filtration bed layer is used to realize deep coalescence and separation of un-layered droplets after growth; finally, the fiber coalescence module is used to realize deep demulsification and coalescence of oil-in-water and water-in-oil, after coalescence and separation, water phase is discharged from the bottom, and oil phase is discharged from the top.

[0028] 2. During operation, high-concentration suspended solids and viscous yellow oil in waste lye adhere and accumulate rapidly in the particle module screen filter section, in order to ensure treatment effect, the system is provided with an intermittent on-off valve to adjust a steam bubble controller to release steam bubbles, so that flow sand particles are fluffy in the fluidized expansion bag, and particle porosity is expanded, under the impact of incoming liquid and steam bubble explosion impact, the flow sand particle module realizes continuous online self-cleaning, and impurities float and collect on the top of the fluidized expansion bag and are periodically discharged.

[0029] 3. Compared with the traditional treatment method, the application adopts a horizontal design and a new treatment method of extraction coupled horizontal flow sand coalescence filtration, which can realize online self-cleaning of the equipment while achieving high-precision and effective oil removal. The application has the advantages of compact structure, small footprint, fast extraction mass transfer, high efficiency, simple operation, energy saving and consumption reduction, and is suitable for treatment of all high-oil-containing, suspended waste water and high-concentration organic waste water extraction, especially complex waste water containing high-viscosity oil. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is the structure diagram of the extraction coupled horizontal flow sand coalescence filtration waste lye oil removal device of the application.

[0031] Figure 2 It is the micro-extraction chaotic reinforcement mixing module of the device of the application, which embodies the micro-extraction and reinforcement mixing process.

[0032] Figure 3 It is the flow sand particle coalescence filtration module of the device of the application, which embodies the process of hydrophilic and hydrophobic particle adhesion and coalescence of two-phase droplets.

[0033] Figure 4 It is the fiber coalescence module of the device of the application, which embodies the process of demulsification, migration and coalescence of two-phase droplets of hydrophilic and hydrophobic fibers.

[0034] Figure 5is a schematic diagram of the effect of a vapor bubble controller of the present application;

[0035] Figure 6 The fluidized state of the fluid sand particles after the fluidizing vapor is passed in.

[0036] 1: horizontal tank body, 2: micro-extraction chaotic enhanced mixing module, 3a: primary fluid sand fine particle coalescence filter module, 3b: secondary fluid sand coarse particle coalescence filter module, 4: fiber coalescence module, 5: extractant circulating pump, 6: flow meter, 7: pressure gauge, 8-11: automatic control valve, 12-13: gate valve

[0037] 2-1: liquid droplet dispersion nozzle

[0038] 2-2: flow resistance block

[0039] 2-3: asymmetric mixing flow channel

[0040] 3-1: support cloth liquid distributor

[0041] 3-2: hydrophilic fluid sand particles

[0042] 3-3: oleophilic fluid sand particles

[0043] 3-4: vapor bubble generator

[0044] 3-5: filler grid

[0045] 4-1: oleophilic fiber

[0046] 4-2: hydrophilic fiber DETAILED DESCRIPTION

[0047] The present application will be further described in conjunction with the accompanying drawings and examples. It should be understood that the following examples are only used to further illustrate the present application, and should not be understood as limiting the scope of protection of the present application. Some non-essential improvements and adjustments made by the skilled in the art based on the content of the present application still fall within the scope of protection of the present application.

[0048] Figure 1The oil removal method and device for the extraction coupled horizontal flow sand coalescence filtration of waste alkali liquor, the oil removal device for the extraction coupled horizontal flow sand coalescence filtration of waste alkali liquor comprises a micro-extraction chaos reinforced mixing module 2, a first flow sand fine particle coalescence filtration module 3a, a second flow sand coarse particle coalescence filtration module 3b and a fiber coalescence module 4. The waste alkali liquor containing butter is fully extracted with an extractant in the micro-extraction chaos reinforced mixing module 2. When the mixed liquid enters the flow sand particle coalescence filtration module 3 through the support liquid distributor 3-1, the solid impurities such as iron filings, butter particles and suspended matters are intercepted by the first flow sand fine particle coalescence filtration module, and the oil and water droplets are preliminarily coalesced and separated. The long and large droplets which have not been separated are subjected to deep coalescence and separation in the second flow sand coarse particle coalescence module. The micro-particle size emulsion droplets are subjected to deep demulsification, coalescence and separation in the fiber coalescence module 4, and are separated in the clarification zone under the action of gravity and buoyancy. The water phase with a larger density moves to the lower part, and the oil phase with a smaller density moves to the upper part. During the operation, the high-concentration suspended matters and viscous butter in the waste alkali liquor are quickly accumulated on the filter screen of the particle module. In order to ensure the treatment effect, the system is provided with intermittent opening and closing valves 8 and 9, a steam bubble controller, a flow sand particle expansion bag, a particle porosity expansion device, a flow sand particle module continuous online self-cleaning device and a waste discharge valve 10 and 11.

[0049] Further, as shown in Figure 3 、 Figure 4 , the waste alkali liquor and the mixed liquid of the extractant collide, intercept, demulsify and coalesce in the flow sand coalescence filtration modules 3 and 4. The oil droplets and water droplets are captured by the oil-wet and water-wet particles, and the small droplets on the particle surface are coalesced into large droplets under the action of surface tension. The oil-wet and water-wet fibers complete the demulsification, coalescence, growth and separation of the water-in-oil droplets in the water phase and the oil-in-water droplets in the oil phase, and deepen the oil-water separation process.

[0050] Example 1

[0051] A petrochemical enterprise adopts the method and device to carry out a pilot test of an extractant-oil-containing waste alkali liquor at different phase ratios. The purified waste alkali liquor is discharged to a recovery treatment process to complete recovery and reuse, and the cracking gasoline serving as an extractant is returned to the process and discharged to a downstream separation tower for treatment and reuse.

[0052] The tangent length of the horizontal tank of the testing device is about 4200 mm, and the diameter is about 600 mm; the filling height of the fluid sand agglomerating filter bed is about 800 mm, the length is about 900 mm, and the remaining fluidization height of the fluidization cavity is about 400 mm; the diameter of the fluidization expansion bag is about 225 mm, the remaining segment height at the top of the fluidization cavity is about 300 mm, and is used for temporary storage of sewage; the diameter of the fiber agglomerating module is the same as the cross section of the tank, and the length is about 500 mm; the first fluid sand agglomerating filter, the second fluid sand agglomerating filter and the fiber agglomerating module are installed at intervals of about 200 mm; the length of the sedimentation area is about 600 mm; the diameter of the oil bag is about 275 mm, and the height is about 500 mm;

[0053] The vapor bubble controller is horizontally installed at the bottom of the agglomerating filter module, directly opposite the cross section of the fluidization expansion bag and having the same diameter, and is in the form of a circumferential nozzle.

[0054] The first fluid sand agglomerating filter module uses particles with a size of 0.5-1 mm, and the oil-wet / hydrophilic particles are mixed at a ratio of 1:1, and the average particle gap is about 0.05 mm; the second fluid sand agglomerating filter module uses particles with a size of 1-2 mm, and the oil-wet / hydrophilic particles are mixed at a ratio of 2:1, and the average particle gap is about 0.25 mm.

[0055] The oil removal step is as follows:

[0056] (1) After the waste lye and the extraction agent dispersed by the nozzle 2-1 are chaotically enhanced mixed by the rhombic flow resistance module 2-2 and the asymmetric mixing flow channel 2-3, the mixture enters the fluid sand agglomerating filter module 3 at a uniform horizontal speed after the balance pressure of the support liquid distributor 3-1, the fluid sand fine particle agglomerating filter module completes the filtration interception and preliminary oil-water droplet coalescence and separation of solid impurities such as iron filings, butter particles and suspended matters, and the fluid sand coarse particle agglomerating filter module completes the deep coalescence and separation of large droplets which have grown but not yet completed the separation;

[0057] (2) After the mixed liquid which has completed the preliminary layering is subjected to deep demulsification and coalescence and separation by the fiber agglomerating module, the layering is completed under the action of gravity and buoyancy;

[0058] (3) During the operation, the high-concentration suspended matters and viscous butter in the waste lye are quickly accumulated on the particle module screen filter section, in order to ensure the treatment effect, the system is provided with intermittent on-off valves 8 and 9 to adjust the release of vapor bubbles by the vapor bubble controller, so that the fluid sand particles are fluidized in the fluidization expansion bag, the particle porosity is expanded, and the fluid sand particle module is continuously and on-line self-cleaned under the impact of the incoming liquid and the explosion impact of the vapor bubbles, the impurities float and are collected at the top of the fluidization expansion bag, and the self-control valves 8 and 9 are opened and closed 5 times, and then the valves 10 and 11 are opened and closed once to discharge the sewage.

[0059] The processing capacity of the present embodiment is 5 m3 / h, and the extractant is the cracking gasoline (mainly C5 components) in the factory area, and the dosage is 5 m3 / h, that is, the waste lye containing oil and the extractant are mixed at a ratio of 1:1 for extraction; the average content of non-dissolved oil in the waste lye is about 5.1%, and the average content of dissolved oil is about 0.2%. After the device is stably operated for a certain period of time, part of the water sample is taken at the inlet and outlet, and the treatment effect is evaluated by an infrared oil measuring instrument, and the results are shown in Table 1. The self-cleaning period of the first flow sand coalescence filtration module is about 24 h, and the time length is about 15 min / time. The self-cleaning period of the second flow sand coalescence filtration module is about 120 h, and the time length is about 10 min / time.

[0060] Table 1

[0061]

Claims

1. A device for removing oil from waste lye solution by extraction coupled horizontal flow coalescence filtration, characterized in that, The device comprises a horizontal tank, a micro-extraction chaotic reinforced mixing module, a first flow sand fine particle coalescence filtration module, a second flow sand coarse particle coalescence filtration module, a fiber coalescence module, and a flow pump for circulating the extractant. The micro-extraction chaotic reinforced mixing module comprises a mixing cavity provided with a flow resistance block outside the front end of the horizontal tank and connected with an asymmetric mixing flow channel in the front part of the horizontal tank, and the mixing cavity is provided with a waste alkali liquid inlet on the side and a liquid droplet dispersion nozzle connected with the extractant circulating pump on the bottom. The first flow sand fine particle coalescence filtration module and the second flow sand coarse particle coalescence filtration module are sequentially arranged in the middle part of the horizontal tank and comprise two fluidized expansion bags above the horizontal tank, each of which is provided with a blowdown port on the top, a particle grid on the top of the fluidized cavity, a particle bed layer below the particle grid, liquid distributors on the two sides of the particle bed layer, and a vapor bubble controller on the bottom. The fiber coalescence module is arranged in the clarification zone behind the second flow sand coarse particle coalescence filtration module and is a woven bed composed of hydrophilic fibers and hydrophobic fibers.

2. The waste lye oil removing device according to claim 1, wherein The small-diameter oil-wet and water-wet particles have a particle size of 0.25-1 mm, a stacking ratio of (1:3)-(3:1), an oil contact angle in water of not more than 70°, and a porosity of 20%-50%.

3. The waste lye oil removing device according to claim 1, wherein The large-diameter oil-wet and water-wet particles have a particle size of 0.5-3 mm, a stacking ratio of (1:3)-(3:1), an oil contact angle in water of not more than 70°, and a porosity of 60%-90%.

4. The waste lye oil removing device according to claim 1, wherein The inner diameter of the liquid droplet dispersion nozzle is 0.5-4 mm, the flow resistance block adopts six diamond-shaped metal blocks, and the asymmetric annular flow channel has three groups.

5. The waste lye oil removing device according to claim 1, wherein When the barrel diameter of the horizontal tank is between 0.2-0.5 m, the particle bed layer height in the first flow sand fine particle coalescence filtration module and the second flow sand coarse particle coalescence filtration module is 0.3-0.8 m; when the barrel diameter is between 1-2 m, the particle bed layer height in the first flow sand fine particle coalescence filtration module and the second flow sand coarse particle coalescence filtration module is 1.5-3.5 m.

6. A method for removing oil from waste lye using the device according to any one of claims 1 to 5, characterized in that, In the fiber coalescence module, the hydrophilic fibers are metal fibers 316L, and the hydrophobic fibers are polytetrafluoroethylene. The method comprises the following steps: Step (1): the waste alkali liquid containing high-viscosity butter from the liquid storage tank or the alkali washing tower enters the micro-extraction chaotic reinforced mixing module through the alkali liquid inlet, the extractant is pressurized to the liquid droplet dispersion nozzle by the extractant circulating pump, and small-diameter micro-liquid droplets are dispersed into the waste alkali liquid and enter the asymmetric annular flow channel with the waste alkali liquid, the ratio of the extractant to the waste alkali liquid is 1:10-1:1, and the alkali liquid-extractant mixed liquid containing oil-in-water and water-in-oil droplets is fully mixed and extracted and then enters the buffer zone. Step (2): The above-mentioned mixed solution enters the first level of flow sand fine particle coalescence filtration module, flows into the particle bed layer of the first level of flow sand fine particle coalescence filtration module through the liquid distributor, and the filtration of solid particles and suspended impurities is completed by using the small particle size particle microchannel in the front half section, so that the butter particles and suspended matter are filtered and intercepted, and the oil / water droplets are captured and coalesced on the lipophilic / hydrophobic particle surface to be preliminarily separated into two phases; Step (3): The liquid distributor flows to the particle bed layer of the second level of flow sand coarse particle coalescence filtration module, and the large droplets that have grown and have not yet completed separation are subjected to deep coalescence and separation; Step (4): The hydrophilic / hydrophobic fiber module in the clarification zone completes the capture, demulsification and coalescence of small particle size droplets, the butter-containing extractant is discharged from the top oil outlet to the extractant recovery process area for further processing, the waste alkali solution from which the butter is removed is discharged from the bottom water phase outlet to the waste alkali solution recovery process area for alkali recovery and utilization; At the same time, in view of the high concentration of suspended matter and viscous butter in the waste alkali solution, the system is provided with an intermittent on-off valve to adjust the vapor bubble controller to release vapor bubbles to make the flow sand particles fluffy in the fluidized expansion bag, the porosity of the particles is expanded, and the flow sand particle module is continuously and on-line self-cleaned under the impact of the coming liquid and the explosion impact of the vapor bubbles, and the impurities are floated and collected at the top of the fluidized expansion bag and are discharged regularly.

7. The method of removing oil from spent caustic according to claim 6, wherein In step (1), the waste alkali solution entering the micro-extraction chaotic enhanced mixing module has a dispersed oil content of less than or equal to 10%, an emulsified oil content of less than or equal to 2%, and an extractant derived from one or more of crude gasoline or benzene series.

8. The method for removing oil from waste lye solution according to claim 6, wherein In step (1), the dispersed particles entering the mixing cavity through the liquid droplet dispersion nozzle have a particle size of 20-100 µm, a spraying pressure difference of 0.2-0.4 MPa, a nozzle diameter of 0.5-4 mm, an average flow velocity of the asymmetric annular flow channel of 0.5-5 m / s, and a turbulent intensity of 10%-20%.

9. The method for removing oil from waste lye solution according to claim 6, wherein In step (2), the fluidization period of the second level of flow sand coarse particle coalescence filtration module is more than five times that of the first level of flow sand fine particle coalescence filtration module, and the horizontal cross-sectional flow velocity in the module is 0.005-0.1 m / s.

10. The method for removing oil from waste lye solution according to claim 6, wherein In step (4), the fluidization vapor is low-pressure vapor at 120°C, and its dosage is 1-20 times the water flow rate according to the water quality of the treated waste alkali solution, the first level of flow sand fluidization period is 48-72 h, and the single fluidization time is 10 min.

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