Membrane separation and purification device for drilling waste liquid of marine drilling rig and use method

Abstract

The invention belongs to the technical field of marine oil and gas well drilling environmental protection equipment, and particularly relates to a marine drilling rig drilling waste liquid membrane separation and purification device and a use method, the device adopts a container tray integrated design, and the device sequentially comprises a cyclone desander, a sedimentation oil removal pool, an ultrasonic demulsification tank, an electromagnetic adsorption flow channel, a filtering tank and a membrane separation unit. Wherein the ultrasonic demulsification tank realizes physical demulsification through an ultrasonic transducer and adsorbs floating oil in combination with a top oil absorption material layer; a plurality of rows of magnetic plates are arranged in the electromagnetic adsorption flow channel to remove magnetic particles; the filtering tank is provided with a high-pressure rotary backwashing system; the membrane separation unit is innovatively connected with a pulse generator in parallel, and an annular gas distributor is integrated on a membrane shell end cover, so that a pulse gas-water collaborative cleaning mechanism is formed. The method effectively solves the technical problems of complex components of the marine drilling waste liquid, fast membrane pollution and poor adaptability of the traditional process by virtue of a multi-stage synergistic pretreatment and core anti-pollution technology, and has the remarkable advantages of high treatment efficiency, long membrane service life and capability of adapting to marine working conditions.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environmental protection equipment for offshore oil and gas drilling, and particularly relates to a membrane separation and purification device for drilling waste liquid of an offshore drilling rig and a use method thereof. BACKGROUND

[0002] In the process of offshore oil and gas drilling, drilling fluid carries cuttings, lubricates the drill bit, and stabilizes the well wall, while generating a large amount of drilling waste liquid. The waste liquid is extremely complex and is a stubborn multi-phase system containing difficult-to-treat emulsified oil, heavy metals, polymers, sulfonated treatment agents, and other drilling fluid additives, high-concentration salts (seawater-based), and cuttings particles (from gravel to colloidal particles).

[0003] The current commonly used pretreatment process of "cyclone sand removal-drug settling" for drilling waste liquid treatment has problems such as incomplete demulsification and low removal efficiency of fine particles, which leads to fast pollution of the subsequent membrane separation system, frequent chemical cleaning, high operating cost, and poor stability. At the same time, traditional land treatment devices are difficult to adapt to the special working conditions of offshore platforms: the requirement of compact integration of equipment due to limited space, and the aggravation of material corrosion in high-salt mist environment. These problems together result in poor effect and insufficient reliability of existing technologies when applied to offshore drilling platforms. SUMMARY

[0004] The present application aims to provide a membrane separation and purification device for drilling waste liquid of an offshore drilling rig and a use method thereof, to solve the technical problems of incomplete demulsification, low removal efficiency of fine particles, fast pollution of the subsequent membrane separation system, frequent chemical cleaning, high operating cost, and poor stability of the current commonly used pretreatment process of "cyclone sand removal-drug settling" for drilling waste liquid treatment. At the same time, traditional land treatment devices are difficult to adapt to the special working conditions of offshore platforms: the requirement of compact integration of equipment due to limited space, and the aggravation of material corrosion in high-salt mist environment. These problems together result in poor effect and insufficient reliability of existing technologies when applied to offshore drilling platforms.

[0005] To achieve the above-mentioned purpose, the specific technical solutions of the membrane separation and purification device for drilling waste liquid of an offshore drilling rig and the use method thereof are as follows: A membrane separation and purification device for drilling wastewater from marine drilling rigs and its usage method include a container pallet. A hydrocyclone desander and a settling oil removal tank are installed on the pallet. The overflow port of the hydrocyclone desander is connected via a pipe to a mixing tank located in front of the settling oil removal tank. A dosing device is installed on this connecting pipe. The device is characterized in that a demulsifying tank is connected via a pipe to the upper and middle clear liquid zone of the settling oil removal tank. Multiple ultrasonic transducers are installed on the periphery of the demulsifying tank, and these transducers are connected to an ultrasonic generator power supply cabinet located on one side of the demulsifying tank. An oil-absorbing material layer is installed at the top of the demulsifying tank. An electromagnetic adsorption channel with a rectangular cross-section is connected via a pipe to the clear liquid outlet at the bottom of the demulsifying tank. Multiple rows of magnetic plates are arranged inside the electromagnetic adsorption channel in the direction of liquid flow. A filter tank is connected to the outlet of the electromagnetic adsorption channel, and a filter tank is installed at the center of the filter tank. The filter tank contains a cylindrical filter screen, and a clean liquid outlet communicating with the interior of the filter screen is located at the bottom. A backwash pump is located at the top of the filter tank, and a backwash pipe is rotatably installed inside the filter screen through the outlet of the backwash pump. Multiple backwash nozzles are installed on the backwash pipe. The clean liquid outlet of the filter tank is connected to a membrane separation unit through a pipeline. The membrane separation unit includes a high-pressure pump and multiple horizontally arranged membrane housings connected in sequence through pipelines. Filter membranes are encapsulated inside each membrane housing. A pulse generator is connected in parallel between the high-pressure pump and the inlet pipe of the membrane housing through a pipeline. The product water ports of the multiple membrane housings are connected. An annular gas distributor is installed inside the end cap of the product water port of each membrane housing. The annular gas distributor has multiple micropores. The membrane separation unit also includes an air pump and a pulse solenoid valve. The air pump is connected to the multiple annular gas distributors through the pulse solenoid valve.

[0006] Furthermore, the oil-absorbing material layer is a chemically resistant modified polypropylene oil-absorbing cotton.

[0007] Furthermore, the multiple rows of magnetic plates in the electromagnetic adsorption channel are permanent magnet plates.

[0008] Furthermore, the cylindrical filter screen in the filter tank is a wedge-shaped wire filter screen.

[0009] Furthermore, the pulse generator is a piston-type or diaphragm-type pulse pump.

[0010] Furthermore, the micropores on the annular gas distributor are evenly distributed along the circumference of the annular distributor, and their injection direction is towards the end face of the filter membrane.

[0011] Furthermore, the filter membrane encapsulated inside the membrane housing is a salt- and oil-resistant composite membrane element.

[0012] Furthermore, the method of using the marine drilling rig wastewater membrane separation and purification device is characterized by comprising the following steps: S1. The marine drilling waste liquid is desanded by a hydrocyclone desander, and then coagulant and flocculant are added to the pipeline through a dosing device. It is then introduced into the mixing tank in front of the settling oil removal tank for mixing, and then gravity settling and oil separation are carried out in the settling oil removal tank. S2. Pump the clear liquid in the upper part of the settling and oil removal tank into the demulsification tank through a liquid pump. Start the ultrasonic generator power cabinet to perform ultrasonic demulsification treatment on the waste liquid through the ultrasonic transducer. After demulsification, the floating oil is absorbed by the top oil-absorbing material layer. S3. The clear liquid at the bottom of the demulsifier flows into the electromagnetic adsorption channel and passes through the gaps between multiple rows of magnetic plates, where the magnetic particles are adsorbed and removed. S4. The liquid after electromagnetic adsorption enters the filter tank and is finely filtered by the cylindrical filter screen. The filtered clear liquid is discharged from the clean liquid outlet at the bottom. The backwash pump and backwash nozzle are started periodically to perform high-pressure rotary backwashing of the filter screen. S5. The filtered clear liquid is pressurized by a high-pressure pump and sent into multiple membrane housings for membrane separation. The produced water is collected. During the membrane separation process, the pulse generator works continuously, applying pulses to the water inlet of multiple membrane housings. At the same time, the pulse solenoid valve opens according to the set cycle, so that the compressed gas provided by the air pump is pulsed to the membrane surface through the annular gas distributor. S6. Wastewater or concentrate generated by the settling oil removal tank, demulsification tank, filter tank and membrane separation unit shall be uniformly discharged to the subsequent treatment system.

[0013] Furthermore, in step S2, the frequency of the ultrasonic demulsification treatment is 20-40 kHz.

[0014] Furthermore, in step S5, the cycle of the pulsed gas flushing is 20-60 seconds for every 20-40 minutes of operation.

[0015] The marine drilling waste liquid membrane separation and purification device and its usage method of the present invention have the following advantages: All units of this device are integrated on a container pallet, forming a highly compact modular structure. This design greatly reduces the equipment's footprint, facilitates overall hoisting, transportation, and deployment, and is suitable for the confined space and tight layout of offshore drilling platforms. Through a multi-stage pretreatment process including sand removal, sedimentation, demulsification, electromagnetic adsorption, and self-cleaning filtration, the system achieves precise removal of contaminants from drilling wastewater step by step, reducing the filtration pressure on the filter membrane. The demulsification tank is equipped with ultrasonic equipment that utilizes physical cavitation to break down stable emulsified oil, and the oil-absorbing material layer promptly adsorbs floating oil, significantly reducing and replacing the use of chemical demulsifiers and avoiding damage to subsequent membrane separation unit components from chemical residues. The electromagnetic adsorption channel features multiple rows of magnetic plates that efficiently adsorb magnetic drilling fluid additives (such as iron ore powder and modified barite) and metal debris from the wastewater, effectively reducing the load on subsequent filtration units. The filter screen inside the filtration tank performs fine filtration of the wastewater, and the included backwashing device (backwash pump, backwash pipe, and backwash nozzle) ensures its self-cleaning capability, avoiding the frequent replacement of traditional filter elements. In the membrane separation unit, a pulse generator is connected in parallel to the water inlet pipe of the membrane housing. During the water inlet process, a high-frequency pressure wave is applied to the membrane housing, which can continuously destroy the initial deposited pollutants on the filter membrane surface and effectively delay the degree of filter membrane fouling. At the same time, an annular gas generator is set in the membrane housing relative to the filter membrane, which can periodically scour the filter membrane with high-pressure gas. During this process, intense gas-liquid turbulence is generated on the filter membrane surface. By physically removing the pollutants attached to the filter membrane surface, the dual physical cleaning mechanism of water inlet pulse and periodic high-pressure airflow pulse forms a synergistic antifouling effect, which can significantly extend the chemical cleaning cycle of the filter membrane, reduce downtime, and greatly improve the service life of the membrane element and the operational stability of the entire purification system. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 For the present invention Figure 1 Enlarged view of region A in the middle; Figure 3 This is a schematic diagram of the connection structure of the demulsifier of the present invention; Figure 4 For the present invention Figure 3 Enlarged view of region B in the middle; Figure 5 This is a schematic cross-sectional view of the internal structure of the demulsifier of the present invention; Figure 6 This is a schematic diagram of the cross-sectional structure of the electromagnetic adsorption flow channel of the present invention; Figure 7 This is a schematic cross-sectional view of the filter tank of the present invention; Figure 8 For the present invention Figure 7 Enlarged diagram of region C in the middle; Figure 9 This is a schematic diagram of the cross-sectional structure of the membrane shell of the present invention; Figure 10 This is a top view of the present invention; The markings in the diagram are as follows: 1. Tray; 2. Cyclone sand separator; 3. Sedimentation oil removal tank; 31. Mixing tank; 4. Dosing device; 5. Demulsifier; 6. Ultrasonic transducer; 7. Ultrasonic generator power supply cabinet; 8. Oil-absorbing material layer; 9. Electromagnetic adsorption channel; 10. Magnetic plate; 11. Filter tank; 12. Filter screen; 13. Backwash pump; 14. Backwash pipe; 15. Backwash nozzle; 16. Membrane separation unit; 17. High-pressure pump; 18. Membrane housing; 19. Filter membrane; 20. Pulse generator; 21. Annular gas distributor; 22. Air pump; 23. Pulse solenoid valve. Detailed Implementation

[0017] To better understand the purpose, structure, and function of this invention, the following detailed description, in conjunction with the accompanying drawings, provides an overview of the marine drilling waste liquid membrane separation and purification device and its usage method.

[0018] like Figures 1-10As shown, the present invention relates to a marine drilling rig waste liquid membrane separation and purification device and its usage method, comprising a container pallet 1, on which a hydrocyclone desander 2 and a settling oil removal tank 3 are installed. The overflow port of the hydrocyclone desander 2 is connected to a mixing tank 31 located in front of the settling oil removal tank 3 via a pipe. A dosing device 4 is installed on the connecting pipe. The device is characterized in that a demulsifying tank 5 is connected to the upper and middle clear liquid zone of the settling oil removal tank 3 via a pipe. Multiple ultrasonic transducers 6 are installed on the periphery of the demulsifying tank 5, and the multiple ultrasonic transducers 6 are connected to an ultrasonic generator power cabinet 7 located on one side of the demulsifying tank 5. An oil-absorbing material layer 8 is installed at the top inside the demulsifying tank 5. An electromagnetic adsorption channel 9 is connected to the bottom clear liquid outlet of the demulsifying tank 5 via a pipe. The electromagnetic adsorption channel 9 has a rectangular cross-section, and multiple rows of magnetic plates 10 are arranged inside it in accordance with the liquid flow direction. A filter tank 11 is connected to the outlet of the electromagnetic adsorption channel 9. A cylindrical filter screen 12 is installed at the center of the filter tank 11. The bottom of the tank 11 is provided with a clean liquid outlet communicating with the inside of the filter screen 12; the top of the filter tank 11 is provided with a backwash pump 13, the outlet of the backwash pump 13 extends into the inside of the filter screen 12 and a backwash pipe 14 is rotatably installed, and multiple backwash nozzles 15 are provided on the backwash pipe 14; the clean liquid outlet of the filter tank 11 is connected to a membrane separation unit 16 through a pipe, and the membrane separation unit 16 includes a high-pressure pump 17 and multiple horizontally arranged membrane housings 18 connected in sequence through pipes. The membrane housing 18 contains a filter membrane 19. A pulse generator 20 is connected in parallel with the inlet pipe of the membrane housing 18 via a pipe. The product water ports of multiple membrane housings 18 are connected. An annular gas distributor 21 is provided inside the product water port end cap of each membrane housing 18. The annular gas distributor 21 has multiple micropores. The membrane separation unit 16 also includes an air pump 22 and a pulse solenoid valve 23. The air pump 22 is connected to multiple annular gas distributors 21 through the pulse solenoid valve 23.

[0019] Combination Figures 1-10As shown, during operation, the drilling waste fluid from the marine drilling rig is pumped into the hydrocyclone desander 2 fixed on the tray 1 for preliminary solid-liquid separation, removing most of the sand and coarse rock cuttings from the waste fluid. The overflow from the hydrocyclone desander 2 is transported to the mixing tank 31 located in front of the settling and oil removal tank 3. A coagulant and flocculant are quantitatively added to the connecting pipe via the dosing device 4. After the chemicals and waste fluid are fully mixed in the mixing tank 31, the waste fluid enters the main body of the settling and oil removal tank 3. In the settling and oil removal tank 3, the flow rate of the mixed fluid is... The process slows down the sedimentation process, allowing the flocculents to settle slowly to the bottom of the tank under gravity, forming a sludge layer. Simultaneously, free oil and demulsified oil droplets in the wastewater, due to their lower density, float to the surface, forming an oil float. To enhance oil-water separation, a chain-plate oil skimmer or dissolved air flotation (DAF) equipment can be installed in the tank. If an oil skimmer is used, the slowly moving scraper scrapes the floating oil into the oil collection tank. If a DAF equipment is used, microbubbles are released to quickly lift oil droplets and fine suspended matter to the surface, forming scum that is then scraped off. The sludge settled at the bottom of the tank is periodically discharged through a bottom sludge discharge valve.

[0020] After sedimentation and oil removal, the clear liquid in the upper part is pumped to the demulsifying tank 5 by a liquid pump. Multiple ultrasonic transducers 6 installed on the periphery of the demulsifying tank 5 emit high-frequency ultrasonic waves into the waste liquid inside the tank under the drive of the ultrasonic generator power cabinet 7. The physical demulsification of the emulsified oil is achieved by utilizing the cavitation effect. The oil sludge that floats to the surface after demulsification is adsorbed by the oil-absorbing material layer 8 laid on the top of the demulsifying tank 5. The clear liquid at the bottom of the demulsifying tank 5 flows into the electromagnetic adsorption channel 9 by gravity. Multiple rows of magnetic plates 10 are set inside the rectangular channel. When the waste liquid flows through the gaps between the magnetic plates 10, the magnetic particles contained therein are efficiently adsorbed and removed.

[0021] The liquid purified by electromagnetic means then enters the filter tank 11. The cylindrical filter screen 12 set in the center of the filter tank 11 performs fine filtration of the liquid and intercepts residual suspended matter. The filtered clear liquid is discharged through the clean liquid outlet at the bottom of the filter tank 11. During the filtration process, when the pressure difference between the inside and outside of the filter screen 12 increases to a set value, the backwash pump 13 at the top of the filter tank 11 is automatically started, which delivers high-pressure water to the rotatable backwash pipe 14 inside the filter screen 12, drives multiple backwash nozzles 15 on it to perform efficient backwashing of the filter screen 12, and at the same time pushes the backwash pipe 14 to rotate, reducing cleaning dead corners. The washed dirt is discharged from the side drain port.

[0022] The purified liquid, after being finely filtered by the filter tank 11, is transported to the membrane separation unit 16. Powered by the high-pressure pump 17, the liquid is pressurized and sent into multiple interconnected membrane housings 18. Each membrane housing 18 encapsulates a filter membrane 19. A pulse generator 20 is connected in parallel between the high-pressure pump 17 and the inlet pipe of the membrane housing 18. The generator continuously applies pulse waves of a specific frequency and amplitude to the inlet water, impacting and removing the initial precipitated contaminants on the surface of the filter membrane 19. At the same time, an annular gas distributor 21 is integrated inside the end cap on the outlet side of each membrane housing 18. The air pump 22 is connected to all the annular gas distributors 21 through the pulse solenoid valve 23 and supplies compressed gas to the annular gas distributors 21 at a set cycle. The gas is ejected from the micropores on its surface, forming a pulsed air sweeping effect on the surface of the filter membrane 19.

[0023] The floating oil on top of the sludge at the bottom of the settling oil removal tank 3, the waste oil adsorbed by the oil-absorbing material layer 8 of the demulsifying tank 5, the backwash wastewater of the filter tank 11, and the concentrated liquid produced by the membrane separation unit 16 are all collected and discharged to the subsequent treatment system for centralized disposal.

[0024] The oil-absorbing material layer 8 is made of chemically resistant modified polypropylene oil-absorbing cotton, which has excellent chemical stability and avoids swelling, degradation or chemical reaction in complex marine drilling waste fluids. At the same time, it can effectively resist the erosion of complex chemical components and high salinity in drilling waste fluids, ensuring a long service life under harsh working conditions and is suitable for the complex operating environment of marine drilling platforms.

[0025] The multi-row magnetic plates 10 in the electromagnetic adsorption channel 9 are permanent magnet plates, which can generate a constant strong magnetic field without external power supply, ensuring inherent safety and zero-energy operation in the complex electrical environment of the offshore platform; at the same time, its stable magnetic force can continuously and efficiently adsorb magnetic drilling fluid additives and metal debris in the waste liquid, avoiding the failure risk that electromagnet coils are prone to in high temperature and vibration environments, and improving the reliability of the equipment in a limited space.

[0026] The cylindrical filter screen 12 in the filter tank 11 is a wedge-shaped wire filter screen. The wedge-shaped wire filter screen is used as the core filter element of the filter tank 11. Its unique V-shaped cross-section slit structure ensures high filtration accuracy and is not easy to clog. At the same time, the surface filtration effect formed makes the pollutants mainly trapped on the outside of the filter screen 12. It can adapt to the high-pressure water flow impact generated by the high-pressure rotary backwashing system, achieve efficient and thorough cleaning effect, ensure the continuous and stable high-flow operation of the filtration system, extend the service life of the filter screen 12, and reduce maintenance frequency and cost.

[0027] The pulse generator 20 is a piston-type or diaphragm-type pulse pump. Using a piston-type or diaphragm-type pulse pump as the pulse generator 20 can generate high-frequency mechanical pulse waves with stable intensity and precise controllable parameters. These pulse waves are transmitted to the interior of each membrane housing 18 through the inlet header, forming a continuous high-frequency shear force on the surface of the filter membrane 19. This effectively destroys the pollutant deposition layer and concentration polarization boundary layer, making it difficult for particulate matter and colloidal pollutants to adhere to the membrane surface. At the same time, the pressure fluctuations caused by the pulse action can also promote reverse diffusion within the membrane channels, slowing down the fouling rate of the filter membrane 19. This cleaning method based on pure mechanical action does not require the participation of chemical agents, providing continuous, efficient and environmentally friendly online antifouling protection for the membrane system.

[0028] like Figure 9 As shown, the micropores on the annular gas distributor 21 are evenly distributed circumferentially along the annular distributor, and their injection direction is towards the end face of the filter membrane 19. Through the design of the micropores on the annular gas distributor 21 being evenly distributed circumferentially and precisely injected towards the end face of the filter membrane 19, excellent cleaning effect of the filter membrane 19 is achieved. By forming an annular air curtain that evenly covers the entire membrane area at the inlet end face of the filter membrane 19, when compressed gas is ejected at high speed from the micropores, a synergistic effect is produced on the surface of the filter membrane 19: the evenly distributed micropores ensure that the airflow does not affect the entire surface of the filter membrane 19. Dead-angle coverage eliminates the cleaning blind spots present in traditional single-point air washing; directional injection ensures that the kinetic energy of the gas acts entirely on the surface of the filter membrane 19, forming strong turbulent shear force in the narrow flow channel between the membrane surface and the inner wall of the membrane shell 18, effectively stripping the adhering contaminants from the filter membrane 19; at the same time, the "air sweeping effect" generated by the tangential movement of the gas along the membrane surface can quickly carry away the stripped contaminants from the membrane surface. This refined airflow distribution pattern enables each pulse air wash to achieve highly efficient cleaning of the surface of the filter membrane 19, significantly improving the antifouling capability and operational stability of the membrane system.

[0029] The filter membrane 19 encapsulated inside the membrane housing 18 is a salt- and oil-resistant composite membrane element. Using this element as the core filtration medium within the housing, and through its specially designed separation layer structure and surface modification technology, it effectively overcomes the complex conditions of high-salt and high-oil marine drilling wastewater. This filter membrane 19 element possesses excellent salt resistance, maintaining a stable desalination rate and membrane flux in high-salinity environments, preventing membrane pore blockage caused by salt crystallization. Simultaneously, its special antifouling surface significantly reduces the adhesion strength of oily substances. Combined with an optimized flow channel design, the pulsed air-water dual-wash system can more efficiently remove oil from the membrane surface, improving the durability of the membrane system when treating extreme wastewater, extending the chemical cleaning cycle, and ensuring that the produced water quality continuously meets marine discharge or reuse standards, significantly reducing operation and maintenance costs.

[0030] The method of using the marine drilling rig waste liquid membrane separation and purification device includes the following steps: S1. The marine drilling wastewater is desanded by the hydrocyclone desander 2, and then coagulant and flocculant are added to the pipeline through the dosing device 4. It is then introduced into the mixing tank 31 in front of the settling oil removal tank 3 for mixing. During the mixing process, mechanical stirring equipment is added to increase the mixing effect and efficiency. Then, gravity settling and oil separation are carried out in the settling oil removal tank 3. The oil skimmer and sludge skimmer are set up to collect the oil and sediment respectively, completing the initial separation of clear liquid. S2. The clear liquid in the upper part of the settling and degreasing tank 3 is pumped into the demulsification tank 5 through a liquid pump. The ultrasonic generator power cabinet 7 is started and the waste liquid is ultrasonically demulsified through the ultrasonic transducer 6. During this process, the waste liquid generates cavitation effect under the action of ultrasonic waves, which destroys the emulsification state of the oil droplets. The demulsified oil droplets collide and coalesce with each other, forming larger oil droplets that float to the top and accumulate at the top of the demulsification tank 5 to form an oil layer. The oil sludge that floats to the top after demulsification is absorbed by the oil-absorbing material layer 8 at the top. S3. The clear liquid at the bottom of the demulsifying tank 5 flows into the electromagnetic adsorption channel 9. The liquid flows through the gaps formed by multiple rows of magnetic plates 10 at a specific flow rate within the channel. Magnetic particles in the wastewater are adsorbed onto the surface of the magnetic plates 10 under the action of the magnetic field. The purified liquid continues to flow forward, passing through the gaps between the multiple rows of magnetic plates 10, where the magnetic particles are adsorbed and removed. As the operating time increases, magnetic substances gradually accumulate on the surface of the magnetic plates 10, which need to be cleaned periodically by a special cleaning device to maintain the adsorption efficiency. S4. The liquid after electromagnetic adsorption enters the filter tank 11 and is finely filtered by the cylindrical filter screen 12. During the filtration process, solid particles are trapped on the outer surface of the filter screen 12, forming a filter cake layer, which causes the filtration resistance to gradually increase. When the preset pressure device of the filter tank 11 detects that the pressure is too high, the backwashing program is automatically started: the backwash pump 13 pumps clean water through the backwash pipe 14 into multiple backwash nozzles 15, which spray the filter screen 12 through the backwash nozzles 15. At the same time, the reaction force of the water spray from the backwash nozzles 15 drives the backwash pipe 14 to rotate, increasing the coverage of the backwash nozzles 15 and avoiding cleaning dead corners. The filtered clean liquid is discharged from the clean liquid outlet at the bottom. The backwash pump 13 and the backwash nozzles 15 are started periodically to perform high-pressure rotary backwashing on the filter screen 12. S5. The filtered clear liquid is pressurized by the high-pressure pump 17 and sent into multiple membrane housings 18 for separation by the filter membranes 19. Water molecules pass through the filter membranes 19 to form product water, while pollutants are trapped to form a concentrated liquid. The product water is collected. During the membrane separation process, the pulse generator 20 works continuously, applying pulses to the water inlet of multiple membrane housings 18 to form alternating pressure changes, which effectively inhibits the deposition of pollutants. At the same time, the pulse solenoid valve 23 opens according to a set cycle, so that the compressed gas provided by the air pump 22 is pulsed to the membrane surface through the annular gas distributor 21 to perform a sweeping gas flushing on the surface of the filter membrane 19. The two cleaning methods work together to significantly extend the service life of the filter membrane 19. S6. Waste liquids and wastes generated by each treatment unit are collected separately through dedicated pipelines. The floating oil and sludge in the settling oil removal tank 3, the waste oil absorption material in the demulsifying tank 5, the backwash wastewater in the filter tank 11, and the concentrate in the membrane separation unit 16 are all classified and transported to the subsequent treatment system for further treatment or resource utilization in accordance with environmental protection requirements, so as to achieve the environmental friendliness of the entire treatment process.

[0031] In step S2, the frequency of ultrasonic demulsification is 20-40 kHz. This frequency range achieves the best balance between demulsification efficiency and energy consumption. The mid-to-high frequency range of 20-40 kHz can generate a sufficiently strong cavitation effect to effectively destroy the oil-water interface film, while avoiding energy dispersion and thermal overload caused by excessively high frequencies. At this frequency, the ultrasound can ensure sufficient penetration depth so that the emulsified oil droplets in all areas of the tank can be treated, and can also generate a moderate micro-jet intensity to promote the collision and coalescence of oil droplets without redispersing them.

[0032] In step S5, the pulsed gas flushing cycle is 20-60 seconds every 20-40 minutes of operation. The 20-40 minute interval matches the accumulation rate of contaminants on the membrane surface, which can intervene in time at the early stage of contamination layer formation to prevent it from developing into stubborn dirt that is difficult to remove. At the same time, the 20-60 second flushing time ensures the maximization of cleaning effect, gives the gas sufficient time to interact with the membrane surface, and avoids energy waste caused by over-flushing.

[0033] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A membrane separation and purification device for drilling waste liquid from a marine drilling rig, comprising a container pallet (1), on which a hydrocyclone desander (2) and a settling oil removal tank (3) are installed, the overflow port of the hydrocyclone desander (2) being connected via a pipe to a mixing tank (31) located in front of the settling oil removal tank (3), and a dosing device (4) being installed on the connecting pipe, characterized in that, The upper and middle clear liquid zone of the settling oil removal tank (3) is connected to a demulsifying tank (5) via a pipe. Multiple ultrasonic transducers (6) are installed on the periphery of the demulsifying tank (5), and these transducers (6) are connected to an ultrasonic generator power cabinet (7) located on one side of the demulsifying tank (5). An oil-absorbing material layer (8) is installed at the top inside the demulsifying tank (5). An electromagnetic adsorption channel (9) is connected to the clear liquid outlet at the bottom of the demulsifying tank (5) via a pipe. (9) has a rectangular cross-section, and multiple rows of magnetic plates (10) are arranged inside in accordance with the direction of liquid flow; a filter tank (11) is connected to the outlet of the electromagnetic adsorption channel (9), a cylindrical filter screen (12) is arranged at the center of the filter tank (11), and a clean liquid outlet communicating with the inside of the filter screen (12) is arranged at the bottom of the filter tank (11); a backwash pump (13) is arranged at the top of the filter tank (11), and the outlet of the backwash pump (13) extends to the filter. The mesh (12) is equipped with a rotating backwash pipe (14), which has multiple backwash nozzles (15). The clean liquid outlet of the filter tank (11) is connected to the membrane separation unit (16) via a pipe. The membrane separation unit (16) includes a high-pressure pump (17) and multiple horizontally arranged membrane housings (18) connected in sequence via pipes. The membrane housings (18) encapsulate filter membranes (19). The high-pressure pump (17) is connected to the inlet pipe of the membrane housing (18). A pulse generator (20) is connected in parallel via pipes between the membrane housings (18); the water outlets of the multiple membrane housings (18) are connected, and an annular gas distributor (21) is provided inside the water outlet side cap of each membrane housing (18), and the annular gas distributor (21) has multiple micropores; the membrane separation unit (16) also includes an air pump (22) and a pulse solenoid valve (23), and the air pump (22) is connected to the multiple annular gas distributors (21) through the pulse solenoid valve (23).

2. The marine drilling rig wastewater membrane separation and purification device according to claim 1, characterized in that, The oil-absorbing material layer (8) is a chemically resistant modified polypropylene oil-absorbing cotton.

3. The marine drilling rig wastewater membrane separation and purification device according to claim 1, characterized in that, The multiple rows of magnetic plates (10) in the electromagnetic adsorption channel (9) are permanent magnet plates.

4. The marine drilling rig wastewater membrane separation and purification device according to claim 1, characterized in that, The cylindrical filter screen (12) in the filter tank (11) is a wedge-shaped wire filter screen.

5. The marine drilling rig wastewater membrane separation and purification device according to claim 1, characterized in that, The pulse generator (20) is a piston-type or diaphragm-type pulse pump.

6. The marine drilling rig wastewater membrane separation and purification device according to claim 1, characterized in that, The micropores on the annular gas distributor (21) are evenly arranged around the annular distributor, and their injection direction is toward the end face of the filter membrane (19).

7. The marine drilling rig wastewater membrane separation and purification device according to claim 1, characterized in that, The filter membrane (19) encapsulated inside the membrane housing (18) is a salt- and oil-resistant composite membrane element.

8. The method using the marine drilling rig wastewater membrane separation and purification device as described in claims 1-7, characterized in that, Includes the following steps: S1. The marine drilling waste liquid is desanded by a hydrocyclone desander (2), and then coagulant and flocculant are added to the pipeline through a dosing device (4). The mixture is then introduced into the mixing tank (31) in front of the settling oil removal tank (3) for mixing. Gravity settling and oil separation are then carried out in the settling oil removal tank (3). S2. Pump the clear liquid in the upper part of the settling oil removal tank (3) into the demulsification tank (5) through a liquid pump. Start the ultrasonic generator power cabinet (7) and use the ultrasonic transducer (6) to perform ultrasonic demulsification on the waste liquid. The oil sludge that floats to the surface after demulsification is adsorbed by the oil-absorbing material layer (8) on top. S3. The clear liquid at the bottom of the demulsifier (5) flows into the electromagnetic adsorption channel (9) and flows through the gap between multiple rows of magnetic plates (10), where the magnetic particles are adsorbed and removed. S4. The liquid after electromagnetic adsorption enters the filter tank (11) and is finely filtered by the cylindrical filter screen (12). The filtered clear liquid is discharged from the bottom clean liquid outlet. The backwash pump (13) and backwash nozzle (15) are started periodically to perform high-pressure rotary backwashing on the filter screen (12). S5. The filtered clear liquid is pressurized by the high-pressure pump (17) and sent into multiple membrane housings (18) for membrane separation (19). The produced water is collected. During the membrane separation process, the pulse generator (20) works continuously to apply pulses to the water inlet of multiple membrane housings (18). At the same time, the pulse solenoid valve (23) opens according to the set cycle, so that the compressed gas provided by the air pump (22) is pulsed and scoured to the membrane surface through the annular gas distributor (21). S6. Wastewater or concentrate generated by the settling oil removal tank (3), demulsifier (5), filter tank (11) and membrane separation unit (16) is uniformly discharged to the subsequent treatment system.

9. The method according to claim 8, characterized in that, In step S2, the frequency of the ultrasonic demulsification treatment is 20-40 kHz.

10. The method according to claim 8, characterized in that, In step S5, the pulsed gas flushing cycle is 20-60 seconds for every 20-40 minutes of operation.

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