A gradient composite particle-based offshore platform oil removal and lithium extraction integrated device and method

Abstract

The application discloses an offshore platform oil removal and lithium extraction integrated device and method based on gradient composite particles. The gradient composite particles are in a spherical core-shell structure, comprising a hydrophobic and oleophilic modified porous shell and a hydrophilic fiber inner core loaded with lithium ion sieves and encapsulated in the shell. The shell intercepts and coalesces oil droplets, and the inner core adsorbs lithium ions, realizing the functions of oil removal and lithium extraction. The device fills the modular bed layer unit of the particles. The bed layer is divided into an upper oil separation zone and a lower lithium extraction zone according to the functional gradient, and is integrated with a monitoring control and cleaning regeneration system. The method comprises the operation steps of adsorption operation, maintenance point judgment based on pressure difference and lithium concentration, and online regeneration or offline replacement of the modular unit. The application deeply integrates the functions of oil removal and lithium extraction, solves the problems of fear of oil stains and long process flow of the adsorption method, has the advantages of strong anti-pollution, convenient operation and maintenance, high lithium ion selectivity, and is suitable for compact space application of offshore platforms.

Description

Technical Field

[0001] This invention belongs to the field of marine wastewater treatment and resource recovery technology, specifically, it relates to an integrated device and method for oil removal and lithium extraction on offshore platforms based on gradient composite particles. Background Technology

[0002] Offshore platform production water is high-salinity, oily wastewater generated during crude oil extraction. Its composition is complex, containing not only dissolved and dispersed oils but also enriched with various valuable metal ions, including lithium. With the surge in demand for lithium resources from industries such as electric vehicles, recovering lithium from this type of wastewater has become an important resource utilization strategy.

[0003] Currently, there are many limitations in the treatment processes for production water from offshore platforms. Traditional treatment methods typically employ a step-by-step process, first removing oil through technologies such as hydrocyclone separation, flotation, and membrane separation, and then extracting lithium ions from the oil-removed water using adsorption, membrane, or extraction methods. However, this multi-step process chain is not only lengthy and requires a large area, but also incurs high equipment investment and operating costs, making it difficult to adapt to the harsh environment of offshore platforms with limited space and load capacity. Furthermore, oily substances easily contaminate and clog subsequent lithium extraction adsorption materials, leading to rapid deactivation and difficulty in regeneration of the adsorption materials, seriously affecting the stability and economy of the entire process. Summary of the Invention

[0004] The purpose of this invention is to overcome the deficiencies in the prior art and provide an integrated oil removal and lithium extraction device and method for offshore platforms based on gradient composite particles, aiming to achieve a highly compact device, long-term stable operation, and maximize lithium recovery.

[0005] The objective of this invention can be achieved through the following technical solutions: This invention provides an integrated oil removal and lithium extraction device for offshore platforms based on gradient composite particles. The integrated device includes a vertical pressure vessel tank. The tank has an outlet at its bottom, an inlet on one side wall, and an oil outlet on the other side wall. The oil outlet is connected to an oil collection bag to collect the separated oil phase, and its axial height is slightly lower than the inlet. Inside the vertical pressure vessel tank, below the inlet, is a cylindrical skid-mounted unit. An annular interlayer between the skid-mounted unit and the inner wall of the vertical pressure vessel tank serves as an oil phase channel. The skid-mounted unit is connected to the vertical pressure vessel tank via a connector. The inner wall of the skid unit is connected to the oil-oil separation zone and the lithium extraction adsorption zone are arranged sequentially along the water inlet flow direction. A first liquid distributor and a second liquid distributor are respectively arranged above the oil-oil separation zone and the lithium extraction adsorption zone, for example, fixed to the inner wall of the skid unit by flange connection. The side wall of the skid unit has several uniform small holes in the axial section corresponding to the oil-oil separation zone, so that the separated oil phase overflows from the side wall to the oil phase channel and floats to the oil outlet for output. A conical component with a matching upper diameter is connected to the lower part of the skid unit, for example, fixed to the lower part of the skid unit by flange connection. The bottom of the conical component is connected to the water outlet.

[0006] In some embodiments of the present invention, the side wall of the vertical pressure vessel tank is provided with an operating hole that communicates with the skid-mounted unit. The operating hole is located in the axial middle section of the skid-mounted unit and has a diameter of 30cm to 60cm. The skid-mounted unit is provided with an openable and closable pressure-bearing and sealing door in the area corresponding to the operating hole for replacing the particle bed in the oil-polymerization separation zone and the lithium extraction adsorption zone.

[0007] In some embodiments of the present invention, a first pressure sensor, a second pressure sensor, an online oil analyzer, and a lithium concentration monitor are arranged from top to bottom on the outside of the vertical pressure vessel tank; the first pressure sensor, the second pressure sensor, the online oil analyzer, and the lithium concentration monitor are all connected to a PLC control unit; the first pressure sensor is located below the first liquid distributor, the second pressure sensor and the online oil analyzer are located above the second liquid distributor, and the lithium concentration monitor is located below the lithium extraction adsorption zone.

[0008] In some embodiments of the present invention, the device further includes a cleaning and regeneration system connected to the PLC control unit, used to automatically trigger water cleaning and acid washing regeneration programs according to a preset differential pressure threshold or lithium ion concentration threshold; specifically, The oil-oil separation zone is connected to a backwash water pump for hydraulic backwashing. Furthermore, during hydraulic backwashing, the oil drain port is closed, and backwash water enters from the outlet and exits from the inlet. The lithium extraction adsorption zone is connected to a regeneration solution supply unit. The regeneration solution is a hydrochloric acid or sulfuric acid solution with a concentration of 0.1 to 1.5 mol / L, which is used to desorb and regenerate the adsorbed composite particles and collect the lithium-rich liquid to recover lithium ions. Furthermore, when desorption and regeneration are performed, the water inlet and oil outlet are closed, and the pickling solution enters from the water outlet. When the pickling solution covers the lithium extraction adsorption zone, the water outlet is closed by a valve. After desorption and regeneration for a period of time, the water outlet is opened to discharge the pickling solution.

[0009] In some embodiments of the present invention, the oil-oil separation zone and the lithium extraction adsorption zone are gradient particle beds formed by gradient composite particles; the gradient composite particles are spherical or near-spherical structures, comprising a hydrophobic and oleophilic porous outer shell and a hydrophobic and oleophilic adsorption core, wherein... The porous shell is a rigid structure with several through pores. After the surface of the porous shell and the inner wall of the pores are modified to be hydrophobic and oleophilic, the contact angle with water is greater than 120°, which is used to intercept, adhere to and promote the coalescence of oil droplets. The adsorption core is a hydrophilic fiber loaded with lithium ion sieves, which is encapsulated in the cavity formed by the porous shell and is used to adsorb lithium ions in the production water that enters the cavity through the through-pores.

[0010] In some embodiments of the present invention, the porous outer shell is made of hydrophobically modified porous ceramic, porous glass, or sintered polymer; the hydrophilic fibers in the adsorption core are made of silica gel fibers, activated alumina fibers, or modified polymer fibers; and the lithium ion sieve is a manganese-based lithium ion sieve or a titanium-based lithium ion sieve.

[0011] Furthermore, the gradient composite particles may also include magnetic nanoparticles located in the hydrophilic fibers of the adsorption core or in the material of the porous shell; furthermore, the magnetic nanoparticles are any one or more of iron oxide, cobalt ferrite, or nickel ferrite.

[0012] In some embodiments of the present invention, the porosity of the porous shell is 40% to 70%; the average diameter of the gradient composite particles is 3 mm to 15 mm.

[0013] In some embodiments of the present invention, the orifice diameter of the first liquid distributor and the second liquid distributor is 1.5 mm to 8 mm.

[0014] Preferably, the orifice diameter of the first liquid distributor is 3mm to 8mm; and the orifice diameter of the second liquid distributor is 1.5mm to 2.5mm.

[0015] Another aspect of the present invention provides a method for oil removal and lithium extraction on offshore platforms based on gradient composite particles, comprising the following steps: The production water from the offshore platform is introduced into the vertical pressure vessel tank through the inlet and then transported to the oil-concentration separation zone via the first liquid distributor. The oil phase in the production water is separated to obtain primary purified water with low oil content. Subsequently, the separated oil phase overflows from the side wall of the skid-mounted unit into the oil phase channel and floats to the oil outlet for output, where it is collected by the oil collection bag. At the same time, the separated primary purified water enters the lithium adsorption zone via the second liquid distributor to deeply adsorb lithium ions in the water. Finally, the production water that has undergone deep oil removal and meets the lithium content standard flows into the conical component and is discharged from the outlet.

[0016] The pollution status of the oil-polymer separation zone is determined based on a preset differential pressure threshold, triggering a water inlet stop and hydraulic backwashing procedure; the adsorption saturation status of the lithium extraction adsorption zone is determined based on a preset lithium ion concentration threshold, triggering a water inlet stop and acid washing regeneration procedure; during this process, after the oil-polymer separation zone and lithium extraction adsorption zone have been running for a long time, the water inlet can be stopped at any time and the pressure-bearing sealed chamber door can be opened to replace and install new particles from the operation port for use.

[0017] In some embodiments of the present invention, when the composite particles used contain the magnetic nanoparticles, after removing them from the bed unit, a further step is included: pouring the composite particles out of the oil-polymerization separation zone or the lithium extraction adsorption zone, and using an external magnetic field to further achieve rapid separation, cleaning and recycling of the particles and waste liquid.

[0018] In some embodiments of the present invention, the filling thickness of the gradient particle bed is 0.5 m to 2.0 m; the bed thickness H1 of the oil-polymerization separation zone is specifically as follows, depending on the oil content of the production water entering the integrated device: When the oil content of the production water is 50–200 mg / L, the bed thickness H1 is 20 cm–35 cm. When the oil content of the production water is 150–350 mg / L, the bed thickness H1 is 65 cm–95 cm. When the oil content of the production water is 350-550 mg / L, the bed thickness H1 is 95 cm-135 cm; The bed thickness H2 of the lithium extraction adsorption zone is 15cm to 65cm.

[0019] Compared with the prior art, the present invention has the following outstanding advantages: 1. This invention provides an integrated oil removal and lithium extraction device for production water on offshore platforms. It utilizes a gradient bed constructed from composite functional particles consisting of a hydrophobic outer shell with interconnected porous structures and a hydrophilic fiber core carrying lithium ions. This achieves sequential integration and synergistic effect between the oil separation zone and the deep lithium extraction adsorption zone within a single tank. This design enables highly efficient interception and coalescence removal of oil droplets from oily production water, along with the tiered deep adsorption and recovery of lithium ions. It simultaneously solves the problems of oil clogging in adsorption methods and the dispersion of traditional multi-stage process equipment within a single process flow, significantly improving lithium resource recovery rate, overall operational stability, and resistance to oil contamination.

[0020] 2. The core processing unit of this invention adopts a standardized, quickly detachable modular particle bed unit design. Different bed thicknesses and functional gradients can be flexibly selected according to actual water quality and treatment capacity requirements. The entire system achieves intelligent operation and maintenance through an integrated monitoring and control system, making regeneration or replacement decisions based on data. Its structure is extremely compact, and the modules are easy to plug and replace. While ensuring a complete and efficient treatment process, it maximizes the saving of valuable space and maintenance manpower costs on offshore platforms. It is particularly suitable for the offshore environment and has significant engineering practicality, ease of operation, and economic benefits throughout its entire life cycle. Attached Figure Description

[0021] Figure 1 A schematic diagram of an integrated oil removal and lithium extraction device for marine platforms based on gradient composite particles; Figure 2 This is a schematic diagram of the porous shell in the composite particles; Figure 3 This is a schematic diagram of the adsorption core in the composite particles.

[0022] Drawing number explanation: 1-Vertical pressure vessel tank, 2-Outlet, 3-Inlet, 4-Oil outlet, 5-Skid-mounted unit, 51-Connector, 6-Oil-polymerization separation zone, 7-Lithium extraction adsorption zone, 81-First liquid distributor, 82-Second liquid distributor, 91-First pressure sensor, 92-Second pressure sensor, 93-Online oil analyzer, 94-Lithium concentration monitor, 10-PLC control unit, 11-Oil phase channel, 12-Conical component, 13-Operating port. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0024] mechanism: This invention is based on the "hydrophobic on the outside, hydrophilic on the inside" particle gradient functional design principle. The oil-oil separation zone preferentially captures and coalesces oil droplets through a porous, hydrophobic-oleophilic shell, causing them to float and separate, while effectively protecting the internal lithium-ion sieve from contamination. The lithium extraction adsorption zone utilizes a lithium-ion sieve supported by hydrophilic fibers in the core to efficiently adsorb the de-oiled aqueous phase. The device can accurately determine its operating status by real-time monitoring of the bed pressure difference and the effluent lithium-ion concentration. The modular bed unit, once saturated with adsorption, can be easily regenerated online to recover the lithium-rich solution, or replaced offline for centralized regeneration. It offers advantages such as strong oil resistance, high lithium-ion selectivity, high resource utilization, and flexible operating modes.

[0025] Preparation Example 1 The method for preparing composite particles includes the following steps: S1. Preparation and modification of the outer shell: Porous alumina ceramic microspheres with an average diameter of about 3 mm to 10 mm were selected as the outer shell substrate. They were immersed in an ethanol solution of 1 wt% heptadecafluorodecyltrimethoxysilane and reacted at 60 °C for 4 h. After being removed, they were dried at 80 °C for 3 h and cured at 150 °C for 1 h to obtain a porous outer shell with superhydrophobic and oleophilic properties (contact angle >150°) on both the surface and the inner wall of the pores. S2. Preparation of the adsorption core: Nanoscale titanium-based lithium ion sieve (HTO) powder (average particle size D50 of about 200 nm) and silica gel sol (SiO2 content 18-22 wt%, average particle size 10-20 nm, pH=3-4) were weighed and mixed at a mass ratio of 1:3. An appropriate amount of deionized water was added to the mixture, and the ratio of deionized water to the total mass of solids in the mixture was (3.5-4.6):1. Then, a 5 wt% polyvinyl alcohol (PVA) binder solution was added. The mixture was stirred at 500 rpm for 3 hours at room temperature until a uniform and stable suspension slurry was formed. The solid content of the slurry was controlled between 18% and 22%. Silica fibers (average diameter 10-20μm) with high specific surface area and good hydrophilicity were selected as the adsorbent carrier. Before use, the silica fibers were fully soaked in deionized water for 30 minutes to open their internal pores and facilitate the loading of the active components. The pretreated wet silica fibers were then completely immersed in the prepared suspension slurry. The entire system was placed in a vacuum environment and maintained at a vacuum level of -0.095 MPa to -0.098 MPa for 40-50 minutes. This process utilizes negative pressure to force the slurry to penetrate into the micropores and mesopores inside the fibers, ensuring sufficient and uniform contact and adhesion between the lithium-ion sieve powder and the fiber carrier. After impregnation, the silica fiber loaded with slurry was removed, and excess slurry was removed by gentle rolling (pressure approximately 0.15 MPa) to initially form a loosely structured fiber felt. Subsequently, the formed fiber felt was dried in an 80°C forced-air drying oven for 4 hours. The initially dried fiber felt was then transferred to a high-temperature oven and cured at 160°C for 1.5 hours to obtain the silica fiber adsorbent material loaded with titanium-based lithium-ion sieves. Through this method, the loading amount (dry basis) of lithium-ion sieves on the fibers can reach 30±2 wt% (the fibers can be cut or combed into fiber bundles of specific sizes according to the needs of subsequent particle assembly). S3. Assembly of composite functional particles: Drill a microhole with a diameter of about 0.5 mm on the porous shell obtained in step S1. Cut the silicone fiber obtained in step S2 and fill it into the cavity inside the ceramic ball through the microhole until it is basically filled. Then seal the microhole with the same alumina slurry (the mixture of porous alumina with an average particle size D50 of 3±2 μm and deionized water at a mass ratio of (2.0-3.5):1). Sinter and fix at 1500±50℃ to obtain composite particles.

[0026] In addition, composite particles with different diameters and loading can be obtained by grinding, sieving, and adjusting the ratio of raw materials.

[0027] Example 1 1.1 Integrated Oil Removal and Lithium Extraction Device for Offshore Platforms Based on Gradient Composite Particles like Figure 1As shown, the apparatus for oil removal and lithium extraction from production water on an offshore platform in this embodiment includes a vertical pressure vessel tank 1. The bottom of the vertical pressure vessel tank 1 has an outlet 2, one side wall has an inlet 3, and the other side wall has an oil outlet 4. The oil outlet 4 is connected to an oil collection bag (not shown in the figure) to collect the oil phase separated from the oil-oil separation zone, and the axial height of the oil outlet 4 is slightly lower than that of the inlet 3. Inside the vertical pressure vessel tank 1, below the inlet 3, a cylindrical skid-mounted unit 5 is arranged. An annular interlayer is left between the skid-mounted unit 5 and the inner wall of the vertical pressure vessel tank 1 as an oil phase channel 11. The skid-mounted unit 5 is connected to the inner wall of the vertical pressure vessel tank 1 via a connector 51. An oil-oil separation zone 6 and a lithium extraction adsorption zone 7 are sequentially arranged inside the skid-mounted unit 5 along the water flow direction. A first liquid separator is respectively arranged above the oil-oil separation zone 6 and the lithium extraction adsorption zone 7. The distributor 81 and the second liquid distributor 82 are fixed to the inner wall of the skid unit 5, for example, by a flange connection; the side wall of the skid unit 5 is provided with several uniform small holes in the axial section corresponding to the oil-polymerization separation zone 6, so that the separated oil phase overflows from the side wall to the oil phase channel 11 and floats to the oil outlet for output; a conical component 12 with a matching upper diameter is connected to the lower part of the skid unit 5, for example, fixed to the lower part of the skid unit 5 by a flange connection, and the bottom of the conical component 12 is connected to the outlet 2; the side wall of the vertical pressure vessel tank 1 is provided with an operation hole 13 that communicates with the skid unit 5. The operation hole 13 is located in the axial middle section of the skid unit 5, and the hole diameter is 30cm to 60cm. The skid unit 5 is provided with an openable and closable pressure-bearing sealed door (not shown in the figure) in the area corresponding to the operation hole 13, for replacing the particle bed in the oil-polymerization separation zone 6 and the lithium extraction adsorption zone 7; The vertical pressure vessel tank 1 is equipped with a first pressure sensor 91, a second pressure sensor 92, an online oil analyzer 93, and a lithium concentration monitor 94 arranged from top to bottom on its exterior. The first pressure sensor 91, the second pressure sensor 92, the online oil analyzer 93, and the lithium concentration monitor 94 are all connected to the PLC control unit 10. The first pressure sensor 91 is located below the first liquid distributor 81, the second pressure sensor 92 and the online oil analyzer 93 are located above the second liquid distributor 82, and the lithium concentration monitor 94 is located below the lithium extraction adsorption zone 7. Furthermore, the device also includes a cleaning and regeneration system (not shown in the figure) connected to the PLC control unit 10, used to automatically trigger water cleaning and acid washing regeneration programs according to a preset differential pressure threshold or lithium ion concentration threshold; specifically, The oil separation zone 6 is connected to a backwash water pump (not shown in the figure) for performing a hydraulic backwashing procedure; furthermore, when hydraulic backwashing is performed, the oil drain port 4 is in a closed state, and the backwash water enters from the outlet port 2 and exits from the inlet port 3. The lithium extraction adsorption zone 7 is connected to a regeneration liquid supply unit (not shown in the figure). The regeneration liquid is a hydrochloric acid or sulfuric acid solution with a concentration of 0.1 to 1.5 mol / L, which is used to desorb and regenerate the adsorbed composite particles and collect lithium-rich liquid to recover lithium ions. Furthermore, when desorption and regeneration are performed, the water inlet 3 and the oil outlet 4 are in a closed state, and the pickling liquid enters from the water outlet 2. When the pickling liquid covers the lithium extraction adsorption zone 7, the water outlet 2 is closed through a valve (not shown in the figure). After desorption and regeneration for a period of time, the water outlet 2 is opened to discharge the pickling liquid.

[0028] Furthermore, the oil-polymerization separation zone 6 and the lithium extraction adsorption zone 7 are gradient particle beds formed by gradient composite particles; the gradient composite particles have a spherical or near-spherical structure, comprising a hydrophobic and oleophilic porous outer shell and a hydrophobic and oleophilic adsorption core, wherein... The porous shell is a rigid structure with several through pores. After the surface of the porous shell and the inner wall of the pores are modified to be hydrophobic and oleophilic, the contact angle with water is greater than 120°, which is used to intercept, adhere to and promote the coalescence of oil droplets. The adsorption core is a hydrophilic fiber loaded with lithium ion sieves, which is encapsulated in the cavity formed by the porous shell and is used to adsorb lithium ions in the production water that enters the cavity through the through-pores.

[0029] Furthermore, the porous outer shell is made of hydrophobically modified porous ceramic, porous glass, or sintered polymer; the hydrophilic fibers in the adsorption core are made of silica gel fibers, activated alumina fibers, or modified polymer fibers; and the lithium ion sieve is a manganese-based lithium ion sieve or a titanium-based lithium ion sieve.

[0030] Furthermore, the gradient composite particles may also include magnetic nanoparticles located in the hydrophilic fibers of the adsorption core or in the material of the porous shell; furthermore, the magnetic nanoparticles are any one or more of iron oxide, cobalt ferrite, or nickel ferrite.

[0031] Furthermore, the porosity of the porous shell is 40% to 70%; the average diameter of the gradient composite particles is 3 mm to 15 mm.

[0032] Preferably, the composite particles in the oil-oil separation zone 6 have an average diameter of 6mm-10mm, a larger average pore size (30μm-70μm) in their porous shell, and stronger oleophobicity; the composite particles in the lithium extraction adsorption zone 7 have an average diameter of 4mm-8mm, a smaller average pore size (10μm-40μm) in their porous shell, and a higher lithium ion sieve loading (35wt%-50wt%) in their adsorption core.

[0033] Furthermore, the orifice diameter of the first liquid distributor 81 and the second liquid distributor 82 is 1.5mm to 8mm; preferably, the orifice diameter of the first liquid distributor 81 is 3mm to 8mm and the orifice diameter of the second liquid distributor 82 is 1.5mm to 2.5mm.

[0034] 1.2 Offshore Platform Oil Removal and Lithium Extraction Method Based on Gradient Composite Particles Combination Figure 1 The method for oil removal and lithium extraction from offshore platforms using the integrated device described in 1.1 above includes the following steps: The production water from the offshore platform is introduced into the vertical pressure vessel tank 1 through the inlet 3 and then transported to the oil-oil separation zone 6 via the first liquid distributor 81. The oil phase in the production water is separated to obtain primary purified water with an oil content of less than 10 mg / L. Subsequently, the separated oil phase overflows from the side wall of the skid-mounted unit 5 into the oil phase channel 11 and floats to the oil outlet 4 for output, where it is collected by the oil collection bag. At the same time, the separated primary purified water enters the lithium adsorption zone 7 via the second liquid distributor 82 to deeply adsorb lithium ions in the water. Finally, the production water that has undergone deep oil removal and meets the lithium content standard flows into the conical component 12 and is discharged from the outlet 2. The pollution status of the oil-polymer separation zone 6 is determined based on a preset differential pressure threshold, triggering a water inlet stop and hydraulic backwashing procedure; the adsorption saturation status of the lithium extraction adsorption zone 7 is determined based on a preset lithium ion concentration threshold, triggering a water inlet stop and acid washing regeneration procedure; during this process, after the oil-polymer separation zone 6 and the lithium extraction adsorption zone 7 have been running for a long time, the water inlet can be stopped at any time and the pressure-bearing sealed chamber door can be opened, and new particles can be replaced and installed from the operation hole 13 for use.

[0035] Furthermore, when the composite particles used contain the magnetic nanoparticles, after removing them from the bed unit, a step is also included: pouring the composite particles out of the oil-polymer separation zone 6 or the lithium extraction adsorption zone 7, and using an external magnetic field to further achieve rapid separation, cleaning and recycling of the particles and waste liquid.

[0036] Furthermore, the filling thickness of the gradient particle bed is 0.5m to 2.0m; based on the oil content of the production water entering the integrated device, the bed thickness H1 of the oil-polymerization separation zone 6 is as follows: When the oil content of the production water is 50–200 mg / L, the bed thickness H1 is 20 cm–35 cm. When the oil content of the production water is 150–350 mg / L, the bed thickness H1 is 65 cm–95 cm. When the oil content of the production water is 350-550 mg / L, the bed thickness H1 is 95 cm-135 cm; The bed thickness H2 of the lithium extraction adsorption zone 7 is 15cm to 65cm.

[0037] Application Example 1 This application example uses the marine platform production water oil removal and lithium extraction device based on gradient functional composite particles from Example 1. The vertical pressure vessel tank 1 has a design specification of Φ1200×1500mm (diameter×total height), the cylinder and end cap are made of 316L stainless steel, the design pressure is 0.8MPa, the design temperature is 80℃, and the design throughput is 5m³ / h. The skid-mounted unit 5 has a diameter of 1180mm.

[0038] The production water of a certain offshore oil and gas field platform has an oil content of 260 mg / L, a suspended solids content of 34.7 mg / L, and a lithium ion concentration of 11.6 mg / L. Based on the oil content in the influent water, the bed thickness H1 is 90 cm and H2 is 60 cm. The composite particles obtained in Preparation Example 1 in the oil-polyester separation zone 6 have an average diameter of 7 mm and an average pore size of 50 μm in their porous shells; the composite particles obtained in Preparation Example 1 in the lithium extraction adsorption zone 7 have an average diameter of 6 mm and an average pore size of 20 μm in their porous shells, and the lithium ion sieve loading in the adsorption core is 40 wt%.

[0039] The method for removing oil and extracting lithium from production water of a marine platform based on gradient functional composite particles, as described in Example 1, is as follows: During operation, the production water of the marine platform is introduced from the inlet 3 via an external booster pump at a dry bed flow rate of 10 m / h. Under the action of the first liquid distributor 81, the water flows uniformly through the oil-polymerization separation zone 6. After treatment in the oil-polymerization separation zone 6, more than 90% of the oil droplets are removed and floated for collection. The oil content in the separated aqueous phase is detected by an online oil analyzer and is reduced to below 5 mg / L. Subsequently, the aqueous phase enters the lithium extraction adsorption zone 7 for further treatment. Finally, the lithium ion concentration in the production water discharged from the outlet 2 can be maintained below 1.5 mg / L for a long period of time, and the total lithium recovery rate exceeds 95%.

[0040] Furthermore, the operation and management of the device adopts an intelligent strategy. The oil-polymer separation zone 6 is mainly clogged due to the trapping of oil and suspended solids. Management is achieved by monitoring the pressure difference between the tank inlet and outlet. When the pressure difference continuously rises from the initial ~0.05MPa to the set value of 0.15MPa, the system prompts that the oil-polymer separation zone 6 needs to be replaced. The saturation of the lithium extraction adsorption zone 7 is determined by online monitoring of the lithium ion concentration at the outlet 2. When the concentration continuously exceeds the set breakthrough point of 5.0mg / L, it indicates that the lithium extraction adsorption zone 7 is saturated and needs to be replaced and regenerated. This can be achieved by first performing a combined air-water pulse backwash (air pressure 0...). The oil film on the outer shell was peeled off by applying a 0.3 MPa water pressure and a 1 Hz pulse frequency for 10 min. Then, the shell was placed in a regeneration tank and desorbed by circulating a 1.0 mol / L hydrochloric acid solution at 50°C for 4 h. The lithium desorption rate exceeded 95%, and a lithium-rich regenerated solution was obtained with a lithium concentration of about 2.0 g / L. This solution can be directly used for subsequent concentration and crystallization. After regeneration, the module was washed with water until neutral, and its dynamic adsorption capacity could be restored to 88% to 90% of the initial capacity. The module can then be reinstalled in the device for recycling.

[0041] Results: After passing through the integrated oil removal and lithium extraction device for offshore platforms based on gradient composite particles, the oil content at the effluent outlet was 6.2 mg / L, the suspended solids content was 3.4 mg / L, and the lithium ion concentration was less than 1.5 mg / L, meeting the discharge and reinjection requirements of offshore platform treated water.

[0042] Application Example 2 This application example uses the marine platform production water oil removal and lithium extraction device based on gradient functional composite particles from Example 1. The vertical pressure vessel tank 1 is enlarged to Φ1200×5000mm, and the material is corrosion-resistant 316L duplex stainless steel. The design pressure rating is increased to 1.0MPa, and the design operating temperature is 60±5℃. The skid-mounted unit 5 has a diameter of 1150mm and is precisely fitted to the inner wall of the tank.

[0043] This application example addresses the more stringent water quality conditions for production water on offshore oil and gas field platforms. Even after preliminary treatment by the front-end three-phase separator, the oil content in the influent is still as high as 162 mg / L, the suspended solids content is ≤40 mg / L, and the lithium ion concentration is 6.5 mg / L. The bed thickness H1 in the oil-polymerization separation zone 6 is 70 cm, and the bed thickness H2 in the lithium extraction adsorption zone 7 is 50 cm. The gradient composite particles filled in the oil-polymer separation zone 6 have an average diameter of 8 mm. Their porous outer shell matrix is ​​an alumina / silica composite porous ceramic with an average pore size controlled at 50 µm and a porosity of 55%. After being modified by fluorosilane surface grafting, the outer shell has a contact angle with water of 138°, thereby enhancing the hydrophobic coalescence effect on emulsified oil droplets (the preparation method is described in Preparation Example 1).

[0044] The gradient composite particles filled in the lithium extraction adsorption zone 7 have an average diameter of 6 mm, and the average pore size of their porous shell is reduced to 20 µm to construct a denser physical barrier. The adsorption core is made of high specific surface area silica fiber supported on nanoscale titanium lithium ion sieve, and the loading is increased to 45 wt% (the preparation method is the same as in Preparation Example 1).

[0045] The method for removing oil and extracting lithium from production water of a marine platform based on gradient functional composite particles, as described in Example 1, is as follows: During operation, the production water of the marine platform is introduced from the inlet 3 via an external booster pump at an empty bed flow rate of 10 m / h. Under the action of the first liquid distributor 81, the water flows uniformly through the oil-polymerization separation zone 6. After treatment in the oil-polymerization separation zone 6, more than 90% of the oil droplets are removed and floated for collection. The oil content in the separated aqueous phase is detected by an online oil analyzer and is reduced to below 9 mg / L. Subsequently, the aqueous phase enters the lithium extraction adsorption zone 7 for deep treatment. Finally, the lithium ion concentration in the production water discharged from the outlet 2 can be maintained below 0.3 mg / L for a long period of time, and the total lithium recovery rate exceeds 95%.

[0046] Furthermore, the operation and management of the device adopts an intelligent strategy similar to that in Application Example 1.

[0047] Results: After passing through the integrated oil removal and lithium extraction device for offshore platforms based on gradient composite particles, the oil content at the effluent outlet was stabilized at 4.2–5.0 mg / L, the suspended solids content was reduced to below 3.0 mg / L, and the lithium ion concentration was below 0.3 mg / L, meeting the discharge and reinjection requirements of offshore platform treated water.

[0048] Comparative Example 1 In order to objectively evaluate the technological advancement of the gradient composite particles and integrated device described in this invention, this comparative embodiment is provided.

[0049] This comparative example uses the same device (tank Φ1200×1500mm) and identical influent water quality as Application Example 1 (oil content 260mg / L, suspended solids 34.7mg / L, lithium ion concentration 11.6mg / L). The difference is that the skid-mounted unit 5 is not filled with the gradient composite particles of this invention, but instead uses a simple layered filling with conventional stepwise processing packing material commonly used in the prior art. Upper oil-separation zone (90cm thick): filled with commercially available fiber ball filter media to trap oil. The lower lithium extraction adsorption zone (thickness 60cm) is filled with a certain company's granular aluminum-based lithium adsorbent (model RTL-91, average particle size 0.5-1.5mm, no outer shell, directly exposed, thermal stability 80℃, expansion rate 5-15%), which is directly laid below the fiber ball layer.

[0050] After the device is started and operated at the same flow rate of 10 m / h, its performance degrades extremely rapidly, as shown in the following details: After only 24 hours of operation, online monitoring showed that the oil removal efficiency of the fiber ball layer dropped significantly, and a large amount of tiny emulsified oil penetrated into the lower layer. Because conventional lithium ion screens lack the physical barrier protection of a porous shell, their microporous structure was quickly covered and blocked by the oil film, i.e., oil poisoning. As a result, the lithium ion concentration in the effluent broke through (>1.0 mg / L) at the 36th hour. At this time, the lithium recovery rate plummeted from the initial 92% to 35%.

[0051] After 48 hours of operation, the pressure difference between the inlet and outlet of the device rapidly increased to 0.45 MPa, far exceeding the 0.15 MPa in the application embodiment of this invention, forcing the device to shut down urgently.

[0052] After shutdown, an attempt was made to regenerate the lower lithium-ion screen by acid washing. However, because the oil was firmly adhered to the surface of the screen by chemical bonding and physical adsorption, conventional acid washing could not remove the oil film. As a result, the adsorption capacity after regeneration was only restored to 15% of the initial value, and the adsorbent was basically scrapped.

[0053] Table 1 below summarizes the key performance indicators of Application Example 1, Application Example 2, and Comparative Example 1, intuitively demonstrating the beneficial effects of the present invention: Table 1 As can be seen from the data in the table above, compared with the prior art, the integrated device based on gradient composite particles of the present invention, when processing oily production water for lithium extraction, utilizes the microscopic synergistic mechanism of shell oil removal and core lithium extraction, which completely solves the industry problem of adsorbent oil pollution poisoning, extends the service life by more than 10 times, and ensures an extremely high lithium resource recovery rate, which has significant substantial features and progress.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present application in any way. Although the present application discloses the preferred embodiment as described above, it is not intended to limit the present application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of the present application using the disclosed technical content are equivalent to equivalent implementation cases. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the technical solution of the present invention are still within the scope of the technical solution.

Claims

1. An integrated oil removal and lithium extraction device for offshore platforms based on gradient composite particles, characterized in that, The device includes a vertical pressure vessel tank with an outlet at the bottom, an inlet on one side wall, and an oil outlet on the other side wall. Inside the vertical pressure vessel tank, below the inlet, is a cylindrical skid-mounted unit with an annular interlayer between it and the inner wall of the tank serving as an oil phase channel. A conical component with a matching upper diameter is connected below the skid-mounted unit, and its bottom communicates with the outlet. Inside the skid-mounted unit, along the direction of water flow, are sequentially arranged an oil-polymerization separation zone and a lithium extraction adsorption zone. Above the oil-polymerization separation zone and the lithium extraction adsorption zone are respectively positioned a first liquid distributor and a second liquid distributor.

2. The apparatus according to claim 1, characterized in that, The side wall of the vertical pressure vessel tank is provided with an operating hole that communicates with the skid-mounted unit. The operating hole is located in the axial middle section of the skid-mounted unit and has a diameter of 30cm to 60cm. The skid-mounted unit is provided with an openable and closable pressure-bearing sealed door corresponding to the area of ​​the operating hole.

3. The apparatus according to claim 1, characterized in that, The vertical pressure vessel is equipped with a first pressure sensor, a second pressure sensor, an online oil analyzer, and a lithium concentration monitor from top to bottom on the outside of the tank. The first pressure sensor, the second pressure sensor, the online oil analyzer, and the lithium concentration monitor are all connected to a PLC control unit. The first pressure sensor and the second pressure sensor are located below the first liquid distributor and above the second liquid distributor, respectively. The online oil analyzer and the lithium concentration monitor are located inside the second liquid distributor and below the lithium extraction adsorption zone.

4. The apparatus according to claim 3, characterized in that, The device also includes a cleaning and regeneration system connected to the PLC control unit, used to automatically trigger water cleaning and acid washing regeneration programs based on a preset differential pressure threshold or lithium ion concentration threshold; specifically, The oil-polymer separation zone is connected to a backwash water pump for performing a hydraulic backwashing process. The lithium extraction adsorption zone is connected to a regeneration liquid supply unit, which is used to desorb and regenerate saturated particles and collect lithium-rich liquid to recover lithium ions.

5. The apparatus according to claim 1, characterized in that, The oil-oil separation zone and the lithium extraction adsorption zone are gradient particle beds formed by gradient composite particles; the gradient composite particles are spherical or near-spherical structures, including a hydrophobic and oleophilic porous shell and a hydrophobic and oleophilic adsorption core.

6. The apparatus according to claim 5, characterized in that, The porous shell is a rigid structure with several through pores. After the surface of the porous shell and the inner wall of the pores are modified to be hydrophobic and oleophilic, the contact angle with water is greater than 120°, which is used to intercept, adhere to and promote the coalescence of oil droplets. The adsorption core is a hydrophilic fiber loaded with lithium ion sieves, which is encapsulated in the cavity formed by the porous shell and is used to adsorb lithium ions in the production water that enters the cavity through the through-pores.

7. The apparatus according to claim 5, characterized in that, The gradient composite particles may also include magnetic nanoparticles.

8. The apparatus according to claim 1, characterized in that, The porosity of the porous shell is 40% to 70%; the average diameter of the gradient composite particles is 3 mm to 15 mm.

9. A method for oil removal and lithium extraction from offshore platforms based on gradient composite particles, employing the apparatus described in any one of claims 1-8, characterized in that, Includes the following steps: The production water from the offshore platform is introduced into the vertical pressure vessel tank through the inlet and then transported to the oil-concentration separation zone via the first liquid distributor. The oil phase in the production water is separated to obtain primary purified water with low oil content. Subsequently, the separated oil phase overflows from the side wall of the skid-mounted unit into the oil phase channel and floats to the oil outlet for output, where it is collected by the oil collection bag. At the same time, the separated primary purified water enters the lithium adsorption zone via the second liquid distributor to deeply adsorb lithium ions in the water. Finally, the production water that has undergone deep oil removal and meets the lithium content standard flows into the conical component and is discharged from the outlet.

10. The method according to claim 9, characterized in that, The thickness of the gradient particle bed is 0.5m to 2.0m; the bed thickness H1 of the oil-polymerization separation zone is specifically determined according to the oil content of the production water entering the integrated unit as follows: When the oil content of the production water is 50–200 mg / L, the bed thickness H1 is 20 cm–35 cm. When the oil content of the production water is 150–350 mg / L, the bed thickness H1 is 65 cm–95 cm. When the oil content of the production water is 350-550 mg / L, the bed thickness H1 is 95 cm-135 cm; The bed thickness H2 of the lithium extraction adsorption zone is 15cm to 65cm.

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