A complete set of equipment and method for sludge multi-stage ultrasonic coupling micro-bubble elution

Abstract

The present application relates to the technical field of ultrasonic coupling exogenous microbubble pressure-bearing, in particular to a multistage ultrasonic coupling microbubble elution complete equipment and method for oil sludge. The technical scheme of the present application is as follows: a multistage ultrasonic coupling microbubble elution complete equipment for oil sludge, comprising a storage tank, a screw pump, a microbubble elution unit, a solid-liquid separation unit and an oil-water filter which are connected through conveying pipes; the storage tank, the screw pump and the microbubble elution unit are circularly connected through conveying pipes to form an elution channel; the storage tank, the screw pump, the solid-liquid separation unit and the oil-water filter are circularly connected through conveying pipes to form a separation channel. An elution method comprises the following steps: step S1) circular elution; step S2) solid-liquid separation; and step S3) oil-water separation. The present application realizes the purpose of strengthening separation and resource utilization of oil sludge, and has the advantages of stable operation, high elution efficiency and wide adaptability.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic coupling exogenous microbubble pressure technology, specifically to a complete set of equipment and methods for multi-stage ultrasonic coupling microbubble elution of oil sludge. Background Technology

[0002] Due to industrial development and urbanization, the impact of pollutants on human health and ecological safety from soils in petroleum, chemical, metallurgical, and mining sites, as well as river sediments, has become increasingly significant. Therefore, oil removal and reduction of heavy metal concentrations in contaminated soils and river sediments have become a focus of international attention. Soil pollution, in particular, is characterized by its hidden, irreversible, and long-term nature, making it a persistent and challenging issue in social discussion. Sludge carries a large number of pathogens, parasites, heavy metals, and salts, including benzene compounds, phenols, and polychlorinated biphenyls (PCBs), which are toxic and harmful substances with foul odors. If these massive amounts of pollutants are discharged directly without treatment, they will not only occupy vast amounts of land but also pollute the surrounding soil, water, and air.

[0003] Currently, remediation technologies for contaminated sites include chemical, physical, and biological methods, as well as combinations thereof. A dynamic equilibrium exists between the gas, water, and solid phases in the soil system. Related studies show a negative correlation between the pollutant content in soil and the particle size distribution; that is, the smaller the particle size, the higher the degree of contamination. Pollutants are mainly adsorbed by fine soil particles such as silt, clay, and humus. These fine particles then adhere to the surfaces of coarse sand and gravel particles. Among these, large soil particles (2-4 mm) constitute a relatively small proportion and have a low degree of contamination; intermediate-sized soil particles (0.076-2 mm) have a high concentration of contaminants, constitute the largest proportion, and exhibit good leaching efficiency; while fine particles smaller than 0.076 mm have a very high concentration of contaminants and exhibit poor leaching efficiency.

[0004] Soil is a porous particle, and the distribution morphology of the oil phase within these particles varies, resulting in different levels of desorption difficulty. Based on the different micro-interface morphologies in oil-bearing particle media, the oil phase in oil-bearing porous particles can be classified into four types: free oil, surface oil, capillary oil, and pore oil. In order of desorption difficulty, the sequence is: free oil < capillary oil < surface oil < pore oil. Multi-stage ultrasonic coupled microbubble technology allows particles to generate sufficiently large convective mass transfer in an ultrasonic field through an external bubble generator to overcome the adsorption force of oil droplets on the particles, thereby achieving deep elution of soil particles of different sizes. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings in the above-mentioned background technology and provide a complete set of equipment and methods for multi-stage ultrasonic coupling microbubble elution of oil sludge.

[0006] The technical solution of this invention is: A multi-stage ultrasonic coupled microbubble elution system for oil sludge includes a storage tank, a screw pump, a microbubble elution unit, a solid-liquid separation unit, and an oil-water filter, all connected by a delivery pipe. The storage tank, screw pump, and microbubble elution unit are circulatedly connected by the delivery pipe to form an elution channel. The storage tank, screw pump, solid-liquid separation unit, and oil-water filter are circulatedly connected by the delivery pipe to form a separation channel.

[0007] The microbubble elution unit includes three microbubble eluents connected in series; the solid-liquid separation unit includes two hydrocyclones connected in series.

[0008] The microbubble eluent includes an eluent housing, an ultrasonic transducer, and an ultrasonic vibrating head connected to the ultrasonic transducer and extending into the eluent housing.

[0009] The washing machine housing is also equipped with a bubble generator; the air pump is connected to each bubble generator through an air supply pipe.

[0010] The outlet of the storage tank is connected to the elution inlet of the first-stage microbubble eluent, the elution outlet of the first-stage microbubble eluent is connected to the elution inlet of the next-stage microbubble eluent, and the elution outlet of the third-stage microbubble eluent is connected to the inlet of the storage tank.

[0011] The outlet of the storage tank is connected to the separation inlet of the primary hydrocyclone separator, the liquid phase outlet of the primary hydrocyclone separator is connected to the separation inlet of the secondary hydrocyclone separator, the liquid phase outlet of the secondary hydrocyclone separator is connected to the oil-water inlet of the oil-water filter, and the drain outlet of the oil-water filter is connected to the inlet of the storage tank; the solid phase outlets of the two hydrocyclones are connected to the inlet of the storage tank.

[0012] The oil-water filter includes a tank, and the interior of the tank, from top to bottom, includes a first inner cavity, a second inner cavity consisting of a filtration zone and an oil discharge zone, a third inner cavity, and a fourth inner cavity; The tank is equipped with an oil-water inlet, an oil outlet, and a water outlet; the filtration zone is arranged from top to bottom as a primary fiber particle bed, a secondary fiber particle bed, and a tertiary fiber particle bed; the third inner cavity is equipped with a corrugated plate; the first inner cavity, the filtration zone, and the third inner cavity are connected from top to bottom; the oil outlet zone is connected to the third inner cavity.

[0013] An elution method, based on the aforementioned multi-stage ultrasonic coupled microbubble elution system for oil sludge, includes the following steps: Step S1) Circulation elution The oil sludge mixture to be treated is stored in the storage tank; the elution channel is opened and the separation channel is closed; the screw pump sends the oil sludge mixture from the storage tank into the microbubble elution unit for elution; the cavitation bubbles generated by the ultrasonic vibrating head remove the oil adhering to the particles; the dense external bubbles generated by the bubble generator improve the oil removal rate; the oil sludge mixture discharged from the microbubble elution unit is returned to the storage tank, and one wash is completed; the washing process is repeated continuously until an oil removal effect of more than 85% is achieved; Step S2) Solid-liquid separation The elution channel is closed and the separation channel is opened; the screw pump sends the oil sludge mixture from the storage tank into the solid-liquid separation unit. The centrifugal force generated by the swirling in the solid-liquid separation unit separates the oil sludge mixture into solid and liquid components. The separated solid particles are returned to the storage tank, and the separated oil-water mixture is sent to the oil-water filter. Step S3) Oil-water separation The oil-water mixture undergoes two-phase separation in an oil-water filter. The oil phase is discharged from the oil outlet and collected, while the water phase is discharged from the water outlet and returned to the storage tank.

[0014] In the microbubble elution unit, the ultrasonic vibration head frequency of the first-stage microbubble elution unit is 50kHz, the ultrasonic vibration head frequency of the second-stage microbubble elution unit is 35kHz, and the ultrasonic vibration head frequency of the third-stage microbubble elution unit is 21kHz.

[0015] In the solid-liquid separation unit, the solid particles separated by the first-stage hydrocyclone separator have a particle size greater than 500 mm, and the solid particles separated by the second-stage hydrocyclone separator have a particle size less than or equal to 500 mm.

[0016] The beneficial effects of this invention are: This invention utilizes a screw pump to drive the flow of an oil-sludge mixture. The cavitation effect generated by an ultrasonic vibrator, coupled with a bubble generator, enhances oil removal from the sludge. A series of first, second, and third-stage ultrasonic vibrators are used to circulate and wash the oil-sludge mixture. The washed-out mixture then enters a two-stage hydrocyclone separator for solid-liquid separation. The liquid phase oil-water mixture overflowing from the two-stage hydrocyclone separator enters an oil-water filter for oil-water separation, while the underflow solid phase enters a storage tank for further circulation and washing. This invention achieves enhanced separation and resource utilization of oil-sludge, and has advantages such as stable operation, high washing efficiency, and wide adaptability. Attached Figure Description

[0017] The following describes some specific embodiments of the invention in a detailed manner by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or components.

[0018] Figure 1 This is a schematic diagram of the connection relationship of the elution device of the present invention.

[0019] Figure 2 This is a schematic diagram of the structure of the oleophilic and hydrophobic fiber particulate filter of the present invention.

[0020] Figure 3 This is a schematic diagram of the structure of the ultrasonic vibrating head of the present invention.

[0021] Figure 4 This is a schematic diagram of the bubble generator of the present invention.

[0022] Figure 5a This is a schematic diagram of the main structure of the cyclone separator of the present invention.

[0023] Figure 5b This is a top view schematic diagram of the cyclone separator of the present invention.

[0024] Figure label: 1. Storage tank; 2. Screw pump; 3. Ultrasonic transducer; 4. Primary microbubble eluent; 5. Secondary microbubble eluent; 6. Tertiary microbubble eluent; 7. Bubble generator; 8. Gas meter; 8.1 Gas valve; 9. Primary hydrocyclone separator; 10. Secondary hydrocyclone separator; 11. Oil-water filter; 12. Oil-water inlet; 12.1 Primary fiber particle bed; 13. Secondary fiber particle bed; 14. Tertiary fiber particle bed; 15. Lower filter cap; 16. Baffle plate; 17. Corrugated plate; 18. Oil drain port; 19. Backwash inlet 20, drain outlet 21, backwash outlet 22, drain outlet 23, upper filter cap 24, conveying pipe 31, main pipe 31.1, washing branch pipe 31.2, separation branch pipe 31.3, recovery branch pipe 31.4, air supply pipe 32, first switching valve 41, second switching valve 42, ultrasonic vibrating head 50, protrusion 51, guide arc head 52, first inner cavity 61, second inner cavity 62, filtration zone 62.1, oil discharge zone 62.2, third inner cavity 63, fourth inner cavity 64. Detailed Implementation

[0025] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the scope of protection of the present invention.

[0026] Through long-term and in-depth research, the applicant has discovered that soil remediation technologies generally include physical separation, soil turning and replacement, airlift, solidification and stabilization, thermal desorption, chemical oxidation, chemical reduction, chemical amendment, chemical leaching / elution, solvent extraction, electrokinetic remediation, animal remediation, phytoremediation, and microbial remediation. However, integrated remediation technologies combining multiple techniques are relatively rare, and traditional remediation technologies suffer from problems such as high energy consumption, high cost, poor remediation effect, and secondary environmental pollution.

[0027] This invention employs a series of techniques: ultrasonic elution, bubble generator-enhanced convection disturbance, liquid-solid cyclone separation of solid particles and oil-water mixtures, and oleophilic-hydrophobic fiber particle filter for oil-water separation. This achieves pollutant particle size classification, efficient oil-water separation, and heavy metal ion removal. It features stable operation, high elution efficiency, and wide adaptability, making it suitable for rapid elution of soil and river sediment in contaminated sites such as petroleum, chemical, metallurgical, and mining industries. After treatment with this invention, the petroleum hydrocarbon content in the sediment is no more than 0.4%, and the oil content in the water is no higher than 100 ppm.

[0028] Example 1 A multi-stage ultrasonic coupled microbubble elution system for oil sludge includes a storage tank 1, a screw pump 2, a microbubble elution unit, a solid-liquid separation unit, an oil-water filter 12, and a delivery pipe 31.

[0029] The equipment includes two channels: an elution channel and a separation channel. The elution channel is formed by a storage tank, a screw pump, and a microbubble elution unit connected in a circulation loop via a delivery pipe. The separation channel is formed by a storage tank, a screw pump, a solid-liquid separation unit, and an oil-water filter connected in a circulation loop via a delivery pipe.

[0030] 1. The following is a detailed description of each component.

[0031] (1) Storage tank The storage tank is equipped with an inlet, an outlet, and a drain outlet 21, and has an agitator inside. The storage tank is used to store an oil sludge mixture, which is a mixture of water, petroleum, and soil (soil of different sizes contaminated with petroleum hydrocarbons or sludge containing heavy metal ions), wherein the mass ratio of water to oil sludge (oil sludge = soil + petroleum) is 10:1.

[0032] (2) Microbubble elution unit The microbubble elution unit is used for repeated elution of oil-sludge mixtures. Specifically: by controlling the bubble parameters generated by the bubble generator, the fluid flow and disturbance intensity are enhanced under the action of bubble agitation, promoting particle friction and collision; as the bubbles move, they collide with oil droplets, partially or entirely adhering to the droplets, or microbubbles, after adhering to the oil droplets, enter the interior of the droplets, forming oil-encapsulated gas-light particles, thereby accelerating the separation of the oil phase from solid particles; simultaneously, the ultrasonic cavitation phenomenon formed by ultrasonic waves of different frequencies generated by the ultrasonic vibrating head induces turbulence, micro-disturbance, interface, and energy-gathering effects, thereby thinning the boundary layer, improving micropore diffusion, and increasing the mass transfer area, thus comprehensively enhancing the mass transfer efficiency and depth of the pollutant desorption process, achieving the goal of highly efficient elution.

[0033] The microbubble elution unit includes three microbubble eluents (tubular ultrasonic washers) connected in series: a primary microbubble eluent 4, a secondary microbubble eluent 5, and a tertiary microbubble eluent 6. A screw pump delivers the oil-sludge mixture from the storage tank into the series of microbubble eluents for multi-stage elution, and then returns it to the storage tank, forming a flow loop to ensure that the oil-sludge mixture can undergo a circulating elution process.

[0034] The microbubble eluent includes a vertically arranged eluent housing, an ultrasonic transducer 3, and an ultrasonic vibrating head 50. The ultrasonic vibrating head is vertically arranged, with its top end connected to the ultrasonic transducer and its bottom end extending vertically downwards into the eluent housing. The microbubble eluent also has an elution inlet and an elution outlet.

[0035] The ultrasonic vibrating head is a long rod shape. The front end of the ultrasonic vibrating head is provided with a flow guiding arc head 52 and several protrusions 51 on the outer circumference. The protrusions can increase the contact surface area between the rod and the mud and microbubble mixture, while changing the flow field morphology when the fluid flows through, creating local turbulence, amplifying the fluid disturbance caused by cavitation, superimposing external microbubble convection, intensifying particle friction and collision, and mechanically tearing the oil film. The flow guiding arc head can disperse the fluid and prevent the slurry from accumulating at the end. The arc surface of the flow guiding arc head can uniformly radiate the ultrasonic field outward, expanding the coverage area of ​​the bottom end.

[0036] The ultrasonic transducer generates cavitation bubbles through an ultrasonic vibrating head to elute the oil-sludge mixture. Specifically: the ultrasonic vibrating head of the first-stage microbubble eluent has a frequency of 50 kHz and is used to remove oil particles with a diameter greater than 600 μm; the ultrasonic vibrating head of the second-stage microbubble eluent has a frequency of 35 kHz and is used to remove oil particles with a diameter of 200-600 μm; and the ultrasonic vibrating head of the third-stage microbubble eluent has a frequency of 21 kHz and is used to remove oil particles with a diameter less than 200 μm. The overall oil removal rate of the oil-sludge mixture after one cycle reaches over 70%.

[0037] The microbubble eluent is also equipped with a bubble generator. The bubble generator 7 is located at the bottom of the inner cavity of the eluent housing, and an external air pump 9 is connected to each bubble generator via an air supply pipe 32. Each branch of the air supply pipe 32 is equipped with an air meter 8 and an air valve 8.1. The bubble generator has a nominal diameter of 20 mm and can generate bubbles with a size of 100 μm.

[0038] The gas generated by the air pump is regulated by the gas meter and then enters the bubble generator, which generates 100μm exogenous microbubbles. The microbubbles can enhance convective disturbance and increase the probability of collision between microbubbles and sludge. At the same time, the non-polar oleophilic properties of the bubbles are used to load the oil phase in the sludge mixture, and the oil droplets are adhered to the microbubbles, which further improves the oil removal rate of the sludge.

[0039] (3) Solid-liquid separation unit The solid-liquid separation unit includes two hydrocyclones (existing equipment) connected in series: a primary hydrocyclone 10 and a secondary hydrocyclone 11. Each hydrocyclone has a separation inlet, a liquid outlet, and a solid outlet. The two hydrocyclones have different specifications. The primary hydrocyclone is a three-inlet hydrocyclone with three separation inlets at the top, which reduces the flow velocity at the mixture inlet and prevents separated solid particles from being carried away by the inner cyclone due to excessive flow velocity, thus affecting the solid removal effect. The secondary hydrocyclone is also a three-inlet hydrocyclone, used for fine particles. It is more sensitive to flow velocity than the primary hydrocyclone, as fine particles are more easily carried away by high-speed fluid; therefore, it also requires flow diversion and velocity reduction. The pressure drop at the separation inlet of each hydrocyclone should not exceed 0.16 MPa, and the liquid flow rate should be 5 m³ / h. The primary hydrocyclone separator separates solid particles with a diameter of 500 mm or larger. The separated solid particles are then introduced into a storage tank for further elution. The liquid phase (oil-water mixture) after desliming in the primary hydrocyclone separator overflows through centrifugal force and enters the secondary hydrocyclone separator. The secondary hydrocyclone separator separates solid particles with a diameter of less than 500 mm. The separated solid particles are also introduced into a storage tank for further elution. The liquid phase (oil-water mixture) after desliming in the secondary hydrocyclone separator overflows through centrifugal force and enters the next stage oil-water filter for oil-water separation. The solid particles separated by the hydrocyclone separator are returned to the storage tank.

[0040] Hydrocyclones utilize swirling currents and centrifugal force to separate mixtures. In a hydrocyclone, the separation of the liquid phase and solid particles is achieved through their different physical properties. The mixture enters the hydrocyclone through the separation inlet, forming a rotating fluid. This rotating fluid generates centrifugal force. Due to the larger mass of the solid particles, they are propelled towards the inner wall of the hydrocyclone by this centrifugal force and deposited downwards along the wall, while the liquid phase rises along the central axis of the equipment and is discharged through the overflow port. In this way, the solid particles and liquid phase are effectively separated. Two-stage hydrocyclones can separate solid particles of different sizes.

[0041] (4) Oil-water filter The oil-water filter is an oleophilic and hydrophobic fiber particle filter. The oil-water filter includes a tank. The tank is provided with an oil-water inlet 12.1 at the top, an oil outlet 19 on the side, a drain outlet 23 at the bottom, and a backwash inlet 20.

[0042] The tank interior is divided into four chambers from top to bottom by a partition 17: a first inner chamber 61, a second inner chamber 62, a third inner chamber 63, and a fourth inner chamber 64. The second inner chamber is further divided by a partition into a filtration zone 62.1 and an oil discharge zone 62.2, arranged horizontally. The filtration zone is provided with a primary fiber particle bed 13, a secondary fiber particle bed 14, and a tertiary fiber particle bed 15, arranged from top to bottom. The third inner chamber is equipped with a corrugated plate 18. The first inner chamber, the filtration zone, and the third inner chamber are connected from top to bottom. The oil discharge zone, the third inner chamber, and the fourth inner chamber are also connected from top to bottom.

[0043] The oil-water inlet connects to the first inner cavity, the oil outlet connects to the oil discharge area, and the water outlet and backwash inlet connect to the fourth inner cavity. Backwashing can be performed through the backwash inlet to prevent particle blockage; in this case, the oil-water inlet serves as the backwash outlet 22. During backwashing, high-pressure clean water is injected into the backwash inlet, and the pressure difference blows away the solid phase material in the blockage of the three-layer fiber particle bed, achieving efficient and stable operation of the device.

[0044] The oil-water mixture discharged from the solid-liquid separation unit enters the oil-water filter through the oil-water inlet at the top of the tank. It then passes through the primary, secondary, and tertiary fiber particle beds in the filtration zone to coalesce and demulsify the mixture. Finally, the oil and water phases are separated by the corrugated plate in the third inner cavity. The coalesced oil phase is recovered from the oil drain on the side wall of the tank, and the water content of the collected oil phase does not exceed 5%. The purified water phase is discharged into the storage tank through the drain at the bottom of the tank, and the oil content of the collected water phase does not exceed 100 ppm.

[0045] The nominal diameter of the tank is 300mm, the tangential length of the tank is 1327mm, and the processing capacity is 5~10m³. 3 / h. The thickness of the primary fiber particle bed, secondary fiber particle bed and tertiary fiber particle bed is 260mm, the porosity is 0.25, 0.4 and 0.6 respectively, the fiber particle size is 3.5μm, and the fiber adopts an X-type weaving method (refer to existing X-type fiber, patent number ZL201410211202.0).

[0046] The oil-water filter breaks down emulsions by using a three-layer fiber particle bed. The fiber particle bed, mainly in the form of packing material, allows emulsified oil droplets to coalesce, merge, and grow. The larger the oil droplet size, the higher the oil removal rate. When the oil-water mixture passes through the fiber particle bed, which is composed of oleophilic solid materials, the small oil droplets in the water adhere to the surface of the fiber particle bed, gradually accumulate, and eventually become large oil droplets, which are then separated more quickly under the action of buoyancy.

[0047] The height of the second inner cavity occupies 1 / 8 to 7 / 8 of the tank height. The filtration zone is wider at the top and narrower at the bottom, and correspondingly, the oil discharge zone is narrower at the top and wider at the bottom. The ratio of the cross-section of the upper part of the filtration zone to the cross-section of the tank is 5 / 6. The ratio of the cross-section of the lower part of the filtration zone to the cross-section of the tank is 1 / 3. An upper filter cap 24 is installed on the partition between the first inner cavity and the filtration zone. The installation opening diameter of the upper filter cap is 50mm (filter gap 0.25mm), and the opening area of ​​all upper filter caps occupies 40% of the area of ​​the partition between the first inner cavity and the filtration zone. A lower filter cap 16 is installed on the partition between the second inner cavity and the filtration zone. The installation opening diameter of the lower filter cap is 50mm (filter gap 0.15mm), and the opening area of ​​all lower filter caps occupies 45% of the area of ​​the partition between the third inner cavity and the filtration zone.

[0048] The corrugated plate is positioned below the oil discharge zone to separate the coalesced oil droplets from the water. Under buoyancy, the oil phase rises to the oil discharge zone and is discharged and collected through the oil discharge port. The purified water is collected through the drain port and introduced into a storage tank. The oil content of the purified water is no higher than 100 ppm.

[0049] The oil-water filter operates at a pressure of 0.4 MPa. Compared to traditional filters, the oil-water filter uses a three-layer filter layer of oleophilic and hydrophobic fiber particles, fixed by baffles. The upper and lower baffles are asymmetrically arranged and equipped with filter caps of different specifications (different filter gap specifications). This forces water to fully pass through the filtration zone. At the same time, a corrugated plate is added to agglomerate oil droplets for secondary agglomeration. The oil phase is discharged from an independent oil outlet. The oil content of the purified water is ≤100ppm, which significantly improves the oil-water separation and regeneration performance compared to traditional equipment.

[0050] 2. The connection relationships of each component are explained in detail below.

[0051] The outlet of the storage tank is connected to the elution inlet of the first-stage microbubble eluent via a delivery pipe 31. The elution outlet of the first-stage microbubble eluent is connected to the elution inlet of the second-stage microbubble eluent. The elution outlet of the second-stage microbubble eluent is connected to the elution inlet of the third-stage microbubble eluent. The elution outlet of the third-stage microbubble eluent is connected to the inlet of the storage tank.

[0052] The outlet of the storage tank is connected to the separation inlet of the first-stage hydrocyclone via a conveying pipe 31. The liquid phase outlet of the first-stage hydrocyclone is connected to the separation inlet of the second-stage hydrocyclone. The liquid phase outlet of the second-stage hydrocyclone is connected to the oil-water inlet of the oil-water filter. The drain outlet of the oil-water filter is connected to the inlet of the storage tank. The solid phase outlets of the two hydrocyclones are connected to the inlet of the storage tank.

[0053] The outlet of the storage tank is connected to the main pipe 31.1 of the delivery pipe 31. The main pipe is then divided into two branches, namely the elution branch pipe 31.2 and the separation branch pipe 31.3. The elution branch pipe connects three microbubble eluents in series between the main pipe and the inlet of the storage tank. The separation branch pipe connects two hydrocyclones and an oil-water filter between the main pipe and the inlet of the storage tank. The hydrocyclones are connected to the inlet of the storage tank through the recovery branch pipe 31.4.

[0054] The main pipe is equipped with a control valve and a screw pump 2, the washing branch pipe is equipped with a first switching valve 41, and the separation branch pipe is equipped with a second switching valve 42.

[0055] Example 2 The soil at a contaminated site has an oil content of 9%. A multi-stage ultrasonic coupled microbubble elution system for oil sludge is installed at this site. The flow rate of the oil sludge mixture delivered by the screw pump is 25 m³ / h. The elution method of this system includes the following steps: Step S1) Circulation elution The storage tank contains a mixture of oily sludge to be treated; When the screw pump starts, the first switching valve opens, the elution channel opens, the second switching valve closes, and the separation channel closes. A screw pump delivers the oil-sludge mixture from the storage tank into the microbubble elution unit for washing. The mixture first enters the microbubble section of the microbubble eluent. Due to ultrasonic cavitation, the collapse of these bubbles generates localized hot spots, accompanied by instantaneous high temperature and pressure, producing intense shock waves and microjets. This enhances the washing effect on petroleum hydrocarbon-contaminated soil. Simultaneously, the bubble generator produces microbubbles to enhance convective disturbance, which strengthens mass transfer and desorption. Under the turbulent bubble flow, the washing rate of pollutants from soil particles is increased. The oil-sludge mixture processed by the microbubble elution unit is returned to the storage tank, completing the washing process in one cycle.

[0056] The first-stage microbubble eluent has an ultrasonic frequency of 50kHz and is used to remove oil adhering to particles with a diameter of 600μm or larger. The second-stage microbubble eluent has an ultrasonic frequency of 35kHz and is used to remove oil adhering to particles with a diameter of 200~600μm. The third-stage microbubble eluent has an ultrasonic frequency of 21kHz and is used to remove oil adhering to particles with a diameter of less than 200μm. Each stage of the microbubble eluent is equipped with an external bubble generator at the bottom to generate 100μm microbubbles to enhance the convection disturbance effect.

[0057] The washing process described above is repeated continuously. By adjusting the number of ultrasonic sludge cycles, the time, and the bubble parameters, the oil sludge is deeply sludge-washed until an oil removal rate of over 85% is achieved.

[0058] Step S2) Solid-liquid separation The screw pump remains running, the first switching valve is closed, the elution channel is closed, the second switching valve is open, and the separation channel is open; The screw pump sends the oil sludge mixture in the storage tank into the solid-liquid separation unit. The centrifugal force generated by the swirling in the solid-liquid separation unit separates the oil sludge mixture into solid and liquid phases. The separated solid particles are returned to the storage tank, and the separated liquid phase (oil-water mixture) is sent to the oil-water filter. The process involves the following steps: The washed oil-sludge mixture first enters the primary hydrocyclone separator from the top, separating solid particles with a diameter of 500 mm or larger. The separated liquid phase overflows from the primary hydrocyclone separator and enters the secondary hydrocyclone separator from the top, separating solid particles with a diameter of 500 mm or smaller. The separated liquid phase (oil-water mixture) overflows from the secondary hydrocyclone separator and is introduced into an oil-water filter for oil-water separation. The solid particles are returned to the storage tank.

[0059] Step S3) Oil-water separation The liquid oil-water mixture enters the oil-water filter from the top. Under the action of gravity, the oil-water mixture undergoes coalescence and demulsification through the primary, secondary, and tertiary fiber particle beds. After demulsification, the oil-water mixture flows through the corrugated plate at the bottom of the filter for oil-water separation. The coalesced oil phase rises to the upper oil layer due to increased buoyancy and is collected and recovered from the oil drain. The purified water phase is discharged to the storage tank through the drain at the bottom of the filter.

[0060] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A complete set of equipment for multi-stage ultrasonic coupling microbubble elution of oil sludge, characterized in that: It includes a storage tank (1), a screw pump (2), a microbubble elution unit, a solid-liquid separation unit, and an oil-water filter (12) connected by a delivery pipe; the storage tank, screw pump, and microbubble elution unit are circulatedly connected by the delivery pipe to form an elution channel; the storage tank, screw pump, solid-liquid separation unit, and oil-water filter are circulatedly connected by the delivery pipe to form a separation channel.

2. The multi-stage ultrasonic coupled microbubble elution system for oil sludge according to claim 1, characterized in that: The microbubble elution unit includes three microbubble eluents connected in series; the solid-liquid separation unit includes two hydrocyclones connected in series.

3. The multi-stage ultrasonic coupled microbubble elution system for oil sludge according to claim 2, characterized in that: The microbubble eluent includes an eluent housing, an ultrasonic transducer (3), and an ultrasonic vibrating head (50) connected to the ultrasonic transducer and extending into the eluent housing.

4. The multi-stage ultrasonic coupled microbubble elution system for oil sludge according to claim 3, characterized in that: The washing machine housing is also equipped with a bubble generator (7); the air pump (9) is connected to each bubble generator through an air supply pipe (32).

5. The multi-stage ultrasonic coupled microbubble elution system for oil sludge according to claim 4, characterized in that: The outlet of the storage tank is connected to the elution inlet of the first-stage microbubble eluent, the elution outlet of the first-stage microbubble eluent is connected to the elution inlet of the next-stage microbubble eluent, and the elution outlet of the third-stage microbubble eluent is connected to the inlet of the storage tank.

6. The multi-stage ultrasonic coupled microbubble elution system for oil sludge according to claim 5, characterized in that: The outlet of the storage tank is connected to the separation inlet of the primary hydrocyclone separator, the liquid phase outlet of the primary hydrocyclone separator is connected to the separation inlet of the secondary hydrocyclone separator, the liquid phase outlet of the secondary hydrocyclone separator is connected to the oil-water inlet of the oil-water filter, and the drain outlet of the oil-water filter is connected to the inlet of the storage tank; the solid phase outlets of the two hydrocyclones are connected to the inlet of the storage tank.

7. The multi-stage ultrasonic coupled microbubble elution system for oil sludge according to claim 6, characterized in that: The oil-water filter includes a tank, and the inside of the tank includes, from top to bottom, a first inner cavity (61), a second inner cavity (62), a third inner cavity (63), and a fourth inner cavity (64), which are composed of a first inner cavity (61), a filtration zone (62.1), and an oil discharge zone (62.2). The tank body is provided with an oil-water inlet (12.1), an oil outlet (19), and a water outlet (23); the filtration zone is provided with a primary fiber particle bed (13), a secondary fiber particle bed (14), and a tertiary fiber particle bed (15) from top to bottom; the third inner cavity is provided with a corrugated plate (18); the first inner cavity, the filtration zone, and the third inner cavity are connected from top to bottom; the oil outlet zone is connected to the third inner cavity.

8. A elution method, based on the multi-stage ultrasonic coupled microbubble elution system for oil sludge as described in claim 7, comprising the following steps: Step S1) Circulation elution The oil sludge mixture to be treated is stored in the storage tank; the elution channel is opened and the separation channel is closed; the screw pump sends the oil sludge mixture from the storage tank into the microbubble elution unit for elution; the cavitation bubbles generated by the ultrasonic vibrating head remove the oil adhering to the particles; the dense external bubbles generated by the bubble generator improve the oil removal rate; the oil sludge mixture discharged from the microbubble elution unit is returned to the storage tank, and one wash is completed; the washing process is repeated continuously until an oil removal effect of more than 85% is achieved; Step S2) Solid-liquid separation The elution channel is closed and the separation channel is opened; the screw pump sends the oil sludge mixture from the storage tank into the solid-liquid separation unit. The centrifugal force generated by the swirling in the solid-liquid separation unit separates the oil sludge mixture into solid and liquid components. The separated solid particles are returned to the storage tank, and the separated oil-water mixture is sent to the oil-water filter. Step S3) Oil-water separation The oil-water mixture undergoes two-phase separation in an oil-water filter. The oil phase is discharged from the oil outlet and collected, while the water phase is discharged from the water outlet and returned to the storage tank.

9. The elution method according to claim 8, characterized in that: In the microbubble elution unit, the ultrasonic vibration head frequency of the first-stage microbubble elution unit is 50kHz, the ultrasonic vibration head frequency of the second-stage microbubble elution unit is 35kHz, and the ultrasonic vibration head frequency of the third-stage microbubble elution unit is 21kHz.

10. The elution method according to claim 8, characterized in that: In the solid-liquid separation unit, the solid particles separated by the first-stage hydrocyclone separator have a particle size greater than 500 mm, and the solid particles separated by the second-stage hydrocyclone separator have a particle size less than or equal to 500 mm.

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