Device for firstly extracting lithium from oil field waste liquid based on selective electrochemical technology

Abstract

The invention discloses an oil field waste liquid lithium extraction device based on a selective electrochemical technology, and relates to the technical field of electrochemical treatment. Comprising a supporting platform, electrodes mounted on the supporting platform, a first electrochemical reaction tank, a second electrochemical reaction tank, a lifting frame mounted on the supporting platform, and a movable lifting trolley mounted on the lifting frame, wherein the first electrochemical reaction tank and the second electrochemical reaction tank are symmetrically arranged in structure; the electrode reaction assembly is installed at the telescopic end of the movable lifting trolley, and the first cleaning pool, the air drying pool and the second cleaning pool are installed on the supporting platform between the first electrochemical reaction pool and the second electrochemical reaction pool. Based on a selective electrochemical technology, efficient and accurate extraction of the lithium resource in the oil field waste liquid is realized; through ultrasonic cleaning and hot air rapid drying, the electrode activity is recovered, and the treatment period is shortened; the modular design is convenient to expand, and industrial requirements are met; resources are recycled, waste is reduced, cross contamination is avoided, and purity is improved; the overall design is efficient, environment-friendly and economical.

Description

Technical Field

[0001] This invention relates to the manufacture of special equipment for environmental protection such as water pollution control, and belongs to the field of electrochemical treatment technology. In particular, it relates to a lithium extraction device for oilfield waste liquid based on selective electrochemical technology. Background Technology

[0002] With the continuous growth of global energy demand, the amount of wastewater generated during oilfield development is also increasing. This wastewater not only contains a large amount of hazardous substances but may also contain valuable metal resources, such as lithium. Lithium, as an important strategic resource, has wide applications in battery manufacturing, new material development, and other fields. However, traditional oilfield wastewater treatment methods often focus on pollutant removal while neglecting resource recovery, especially lithium recovery. This not only wastes resources but may also cause long-term environmental pollution.

[0003] Currently, while some lithium extraction technologies exist on the market, most are designed for high-concentration lithium solutions. Technologies for directly extracting lithium from low-grade, complex-composition oilfield wastewater are still immature. Existing physical and chemical lithium extraction methods suffer from high costs, low efficiency, and secondary pollution, making them unsuitable for industrial applications. Therefore, developing an efficient, environmentally friendly, and economical lithium extraction technology from oilfield wastewater is of great significance for achieving resource recycling and protecting the ecological environment.

[0004] Against this background, the present invention proposes a lithium extraction device for oilfield wastewater based on selective electrochemical technology. Summary of the Invention

[0005] The purpose of this invention is to provide a lithium extraction device for oilfield wastewater based on selective electrochemical technology, which achieves efficient extraction and recovery of lithium resources from oilfield wastewater through electrochemical methods.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: This invention relates to a lithium extraction device for oilfield wastewater based on selective electrochemical technology. It includes a support platform, a first and second electrochemical reaction tank with symmetrically arranged electrodes and structures mounted on the support platform, a hoisting frame mounted on the support platform, a mobile lifting vehicle mounted on the hoisting frame, an electrode reaction assembly mounted on the telescopic end of the mobile lifting vehicle, and a first cleaning tank, a drying tank, and a second cleaning tank mounted on the support platform between the first and second electrochemical reaction tanks. A hot air blower is connected to the air inlet of the drying tank. The electrode reaction assembly participates in the electrochemical reaction in the first electrochemical reaction tank for the first time. The initial anode material of the electrode reaction assembly is lithium iron phosphate, and the initial cathode material is iron phosphate.

[0007] As a preferred embodiment of the present invention, it further includes an oilfield wastewater supply pool for holding filtered crude purified oilfield wastewater, a water supply pool for holding cleaning water, a wastewater collection pool for holding lithium-extracted wastewater from oilfield wastewater, an anolyte storage pool for holding anolyte, and a wastewater pool for holding cleaning wastewater.

[0008] As a preferred embodiment of the present invention, the first electrochemical reaction cell includes an anode reaction cell outer shell, an anion exchange membrane separator, a gasket, and a cathode reaction cell outer shell, which are connected as a single unit by a plurality of bolts and nuts; the lower end of the anode reaction cell outer shell is fixed to the upper surface of the support platform; the anode reaction cell outer shell is provided with a row of anode electrolytic cells with side and top openings for accommodating anode electrolyte; the cathode reaction cell outer shell is provided with a row of cathode electrolytic cells with side and top openings for accommodating oilfield waste liquid; each pair of anode electrolytic cells and cathode electrolytic cells in the first electrochemical reaction cell are separated by an anion exchange membrane separator; the anode electrolytic cells are provided with a first inlet / outlet hole and a first overflow hole; a row of the first The inlet and outlet ports are connected to the anode electrolyte storage tank through the first conveying pipeline assembly; a row of first overflow ports are connected to the anode electrolyte storage tank through the first overflow pipe; the cathode electrolysis cell is provided with a second inlet and outlet port and a second overflow port; a row of second inlet and outlet ports are connected to the oilfield waste liquid supply tank and the waste liquid collection tank through the second conveying pipeline assembly; a row of second overflow ports are connected to the oilfield waste liquid supply tank through the second overflow pipe; an anode contact electrically connected to the anode reaction material of the electrode reaction assembly is embedded in the upper end of the anode reaction tank shell; a cathode contact electrically connected to the cathode reaction material of the electrode reaction assembly is embedded in the upper end of the cathode reaction tank shell.

[0009] As a preferred embodiment of the present invention, the first conveying pipeline assembly includes a first metering pump installed on the anolyte storage tank and drawing liquid from the anolyte storage tank, and a first integrated pipeline connecting a row of first inlet / outlet holes to the anolyte storage tank; a first solenoid valve is installed on a branch pipe connecting the first integrated pipeline to the first metering pump; a second solenoid valve is installed on a branch pipe directly connecting the first integrated pipeline to the anolyte storage tank. The second conveying pipeline assembly includes a second metering pump installed on the oilfield wastewater supply tank and drawing liquid from the oilfield wastewater supply tank, and a second integrated pipeline connecting a row of second inlet / outlet holes, the oilfield wastewater supply tank, and the wastewater collection tank; a third solenoid valve is installed on a branch pipe connecting the second integrated pipeline to the second metering pump; a fourth solenoid valve is installed on a branch pipe connecting the second integrated pipeline to the wastewater collection tank. The structural features of the second electrochemical reaction tank are symmetrically arranged with respect to the first electrochemical reaction tank about the drying tank, and its connection supply and discharge relationship is the same as that of the first electrochemical reaction tank, which will not be described again here.

[0010] As a preferred embodiment of the present invention, the hoisting frame includes two gantry frames fixed to the support platform and arranged side by side; the columns of the two gantry frames are connected as one unit by multiple fixed crossbars; a pair of guide rails are installed on the upper ends of the two gantry frames, and limit baffles are provided at the ends of the guide rails; a rack is installed on the upper end of one of the gantry frames; a first position detection sensor, a second position detection sensor, a third position detection sensor, a fourth position detection sensor, and a fifth position detection sensor are sequentially installed on the side of the crossbeam of one of the gantry frames, corresponding to the positions of the first electrochemical reaction tank, the first cleaning tank, the drying tank, the second cleaning tank, and the second electrochemical reaction tank.

[0011] As a preferred embodiment of the present invention, the mobile lifting vehicle includes a horizontal frame; two rows of sliders are installed below the horizontal frame and are linearly slidably connected to a pair of guide rails; a linear electric cylinder is vertically installed on the horizontal frame; the lower end of the linear electric cylinder extends through the two gantry frames and connects to the middle of the electrode reaction assembly; a servo motor for horizontal movement drive is also installed on the horizontal frame; a gear that engages with the rack is installed on the output shaft of the servo motor; a sixth position detection sensor is installed on one side of the horizontal frame corresponding to the position of the electrode reaction assembly via an L-shaped bracket.

[0012] As a preferred embodiment of the present invention, the electrode reaction assembly includes a first conductive substrate and a second conductive substrate arranged side by side; the first conductive substrate and the second conductive substrate are fixed together by an inverted T-shaped insulating retainer, and the insulating retainer has a first open channel and a second open channel respectively below the first conductive substrate and the second conductive substrate; the center distance between the first open channel and the second open channel is the same as the center distance between the anode and cathode of the first electrochemical reaction cell; an external retainer is installed on the side walls and the upper half of the insulating retainer by a number of sets of bolts and nuts; a connecting plate that connects and cooperates with the telescopic end of the linear electric cylinder is provided at the middle of the upper end of the external retainer; a number of first conductive base rods are arranged on the lower surface of the first conductive substrate along the center line of the first open channel; an anode lithium iron phosphate layer is laminated on the outside of the first conductive base rods; a number of second conductive base rods are arranged on the lower surface of the second conductive substrate along the center line of the first open channel; a cathode iron phosphate layer is laminated on the outside of the second conductive base rods; the first conductive substrate is conductive when in contact with the anode contact; the second conductive substrate is conductive when in contact with the cathode contact.

[0013] As a preferred embodiment of the present invention, the first cleaning tank includes a rectangular trough with an upper opening; a first partition is provided in the middle of the rectangular trough; ultrasonic generating devices are installed on both side walls of the rectangular trough; two water inlet pipes are provided at one end of the rectangular trough; a third metering pump is installed on the water supply tank, and the third metering pump draws water from the water supply tank; the water inlet pipes are connected to the water outlet end of the third metering pump; two water outlet pipes are provided at the bottom of the other end of the rectangular trough, and two third overflow pipes are provided in the upper half, with the ends of the third overflow pipes communicating with the water outlet pipes; a fifth solenoid valve is installed on the direct connection section between the water outlet pipe and the rectangular trough; the structural features of the second cleaning tank and the structural features of the first cleaning tank are symmetrically arranged with respect to the drying tank.

[0014] As a preferred embodiment of the present invention, a drying groove is formed at the upper end of the drying tank; a guide channel is formed at one end of the drying tank symmetrically arranged with respect to the drying groove; a row of downwardly arranged air blowing channels is formed on the wall between the guide channel and the drying groove; the bottom of the drying groove is lower than the bottom of the guide channel; the wall between the opening ends of the two guide channels is formed as a gas-distributing cone; the two guide channels are connected to the air outlet of the hot air blower; and a second partition is provided in the middle of the drying groove.

[0015] As a preferred embodiment of the present invention, a protective cover is installed on the first cleaning tank, the drying tank, and the second cleaning tank; the upper end of the drying tank is lower than the upper end of the first cleaning tank; the protective cover includes two rectangular frames that are fastened to the upper ends of the first and second cleaning tanks; a protective baffle is fixed to each of the two side walls along the length of the rectangular frames, and the lower end of the protective baffle contacts the upper surface of the support platform; the two ends of the two rectangular frames are connected as one unit by two fixed connecting rods; a pair of symmetrically arranged guide plates are fixed between the two fixed connecting rods and the two rectangular frames, and the lower end of the guide plates extends to the upper edge of the drying groove.

[0016] The present invention has the following beneficial effects: This invention enables continuous and directional migration of lithium ions by alternating electrochemical reactions in two electrochemical reaction tanks through an electrode reaction assembly, significantly improving lithium extraction efficiency and achieving efficient extraction of lithium resources from oilfield wastewater.

[0017] The device design of this invention includes an electrolyte recycling system. After lithium ions in the anolyte are enriched through electrochemical reaction, they can be recycled back to the electrochemical reaction cell, forming a resource closed loop and reducing resource waste.

[0018] Compared to traditional lithium extraction methods, this invention avoids the use of large amounts of chemical reagents, reducing secondary pollution. Furthermore, the electrochemical lithium extraction process involves simply applying electricity, resulting in low energy consumption and aligning with the green and low-carbon development philosophy.

[0019] The device of this invention realizes the automatic transfer and positioning of the electrode reaction assembly through a mobile lifting vehicle and a hoisting frame. Combined with a position detection sensor, it ensures the precise execution of the electrochemical reaction, reduces the difficulty of manual operation, and improves production efficiency.

[0020] This invention utilizes a reciprocating electrochemical reaction mechanism to maintain the electrode material in a dynamic equilibrium state, thereby slowing down capacity decay and extending service life. Simultaneously, periodic perturbation of the electrode surface double layer reduces polarization accumulation, maintains a low overpotential, and improves energy efficiency.

[0021] This invention utilizes ultrasonic cleaning technology to efficiently remove deposits from electrode surfaces and restore electrode activity. Combined with a hot air rapid drying design, it significantly shortens the processing cycle. At the same time, it uses a protective cover and a flow guiding structure to reduce dripping losses and optimize the workflow, achieving efficient, clean, and automated control of the cleaning and drying process. This effectively improves the overall efficiency and product purity of lithium extraction operations.

[0022] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of a lithium extraction device for oilfield waste liquid based on selective electrochemical technology according to the present invention.

[0025] Figure 2 for Figure 1 A structural diagram from another perspective.

[0026] Figure 3 for Figure 2 A magnified view of a portion of point A in the middle.

[0027] Figure 4 for Figure 2 A magnified view of a section at point B.

[0028] Figure 5 for Figure 1 The front view.

[0029] Figure 6 for Figure 5 A magnified view of a section at point C.

[0030] Figure 7 for Figure 1 Top view.

[0031] Figure 8 for Figure 1 The right view.

[0032] Figure 9 for Figure 1 A partial structural cross-sectional view.

[0033] Figure 10 for Figure 9 A magnified view of a section at point D.

[0034] Figure 11 for Figure 9 A magnified view of a section at point E in the middle.

[0035] Figure 12 for Figure 9 A magnified view of a section at point F.

[0036] Figure 13 for Figure 1 A partial structural diagram.

[0037] Figure 14 for Figure 12A structural diagram from another perspective.

[0038] Figure 15 This is a schematic diagram of the outer shell of the cathode reaction cell.

[0039] Figure 16 This is a schematic diagram of the electrode reaction assembly.

[0040] Figure 17 This is a schematic cross-sectional view of the electrode reaction assembly.

[0041] Figure 18 This is a schematic diagram of the protective shield.

[0042] The attached diagram lists the components represented by each number as follows: 1-Supporting platform, 2-First electrochemical reaction tank, 3-Second electrochemical reaction tank, 4-Lifting frame, 5-Mobile lifting vehicle, 6-Electrode reaction assembly, 7-First cleaning tank, 8-Drying tank, 9-Second cleaning tank, 10-Hot air blower, 11-Oilfield waste liquid supply tank, 12-Water supply tank, 13-Waste liquid collection tank, 14-Anode electrolyte storage tank, 15-Wastewater tank, 16-Protective cover, 17-First conveying pipeline assembly, 18-First overflow pipe, 19-Second conveying pipeline assembly, 20-Second overflow pipe, 21-Anode contact, 22-Cathode contact 201-Anode reaction cell outer shell, 202-Cathode reaction cell outer shell, 203-Anion exchange membrane separator, 2011-Anode electrolytic cell, 2012-First inlet / outlet port, 2013-First overflow port, 2021-Cathode electrolytic cell, 2022-Second inlet / outlet port, 2023-Second overflow port, 41-Gantry frame, 42-Guide rail, 43-Rack, 31-First position detection sensor, 32-Second position detection sensor, 33-Third position detection sensor, 34-Fourth position detection sensor, 35-Fifth position detection sensor Device, 51-Horizontal frame, 52-Linear electric cylinder, 53-Servo motor, 54-Gear, 55-L-shaped bracket, 56-Sixth position detection sensor, 61-First conductive substrate, 62-Second conductive substrate, 63-Insulating retainer, 64-First open channel, 65-Second open channel, 66-External retainer, 67-Connecting plate, 68-First conductive base rod, 69-Anode lithium iron phosphate layer, 610-Second conductive base rod, 611-Cathode iron phosphate layer, 71-Rectangular tank, 72-First partition, 73-Ultrasonic generator, 74-Water inlet Pipe, 75-Third metering pump, 76-Water outlet pipe, 77-Third overflow pipe, 78-Fifth solenoid valve, 81-Air drying groove, 82-Air guide channel, 83-Air blowing channel, 84-Air distribution cone, 85-Second partition, 161-Rectangular frame, 162-Protective baffle, 163-Fixed connecting rod, 164-Flow guide ramp, 171-First metering pump, 172-First integrated pipe, 173-First solenoid valve, 174-Second solenoid valve, 191-Second metering pump, 192-Second integrated pipe, 193-Third solenoid valve, 194-Fourth solenoid valve. Detailed Implementation

[0043] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0044] Specific Implementation Example 1: Please refer to Figure 1-18As shown, this invention is a lithium extraction device for oilfield wastewater based on selective electrochemical technology. It includes a support platform 1, a first electrochemical reaction tank 2 and a second electrochemical reaction tank 3 with symmetrically arranged electrodes and structures mounted on the support platform 1, a hoisting frame 4 mounted on the support platform 1, a mobile lifting vehicle 5 mounted on the hoisting frame 4, an electrode reaction assembly 6 mounted on the telescopic end of the mobile lifting vehicle 5, and a first cleaning tank 7, a drying tank 8, and a second cleaning tank 9 mounted on the support platform 1 between the first and second electrochemical reaction tanks 2 and 3. A hot air blower 10 is connected to the air inlet of the drying tank 8. The electrode reaction assembly 6 participates in the electrochemical reaction for the first time in the first electrochemical reaction tank 2. The initial anode material of the electrode reaction assembly 6 is lithium iron phosphate. The initial cathode material of the electrode reaction assembly 6 is iron phosphate.

[0045] The principle of selective electrochemistry in the device of this application is as follows: Anode reaction: LiFePO4−e - →Li + +FePO4. In this reaction, LiFePO4 loses electrons, and lithium ions are released from the LiFePO4 structure and enter the electrolyte. Simultaneously, LiFePO4 is converted to FePO4. This is a delithiation process, realizing the release of lithium ions from the anode material. When energized, the LiFePO4 at the anode continues to delithigate, and the lithium ion concentration in the electrolyte in the anode region gradually increases.

[0046] Cathode reaction: FePO4 + e - +Li + →LiFePO4 (A similar reaction occurs where a FePO4 electrode accepts lithium ions and electrons in lithium-ion-containing oilfield wastewater to generate LiFePO4). At the cathode, lithium ions and electrons combine and embed into the corresponding material structure to form LiFePO4; this is a lithium insertion process. When energized, the lithium ion concentration in the oilfield wastewater in the cathode region decreases and is fixed into the electrode.

[0047] When the electrode reaction assembly 6 is transferred from the first electrochemical reaction cell 2 to the second electrochemical reaction cell 3, the corresponding electrodes and electrolytic cells are symmetrically arranged. When energized, the above-mentioned anode reaction and cathode reaction are carried out again. Lithium is extracted as soon as energization is applied, and electrical energy is not wasted, thus achieving lithium ion enrichment in the electrolyte in the anode region.

[0048] The specific operating steps are as follows: 1. Initial Lithium Extraction: Upon initial use, the mobile lifting vehicle 5 moves the electrode reaction assembly 6 above the first electrochemical reaction cell 2 and lowers the electrode reaction assembly 6 into the first electrochemical reaction cell 2. When energized, the anodic reaction occurs: LiFePO4−e - →Li + +FePO4 reacts with the cathode: FePO4 + e- +Li +→LiFePO4. Lithium is extracted upon energization, enabling the enrichment of lithium ions in the anolyte and the precise extraction of lithium from oilfield wastewater.

[0049] 2. Electrode Transfer and Cleaning: After the lithium extraction time in the first electrochemical reaction cell 2 is reached, the moving lifting vehicle 5 lifts the electrode reaction assembly 6 upwards and suspends it for several minutes until it stops dripping. Then, the moving lifting vehicle 5 moves the electrode reaction assembly 6 above the first cleaning cell 7, and then lowers the electrode reaction assembly 6 into the first cleaning cell 7 for ultrasonic cleaning for several minutes before lifting it up again.

[0050] 3. Air drying process: The mobile lifting vehicle 5 moves the electrode reaction assembly 6 above the air drying tank 8, and then lowers the electrode reaction assembly 6 into the air drying tank 8 for air drying. The hot air blower 10 is started, and hot air is blown into the air drying groove 81 through the air guide channel 82 and the air blowing channel 83. After air drying for several minutes, it is lifted up again.

[0051] 4. Secondary Lithium Extraction: The mobile lifting vehicle 5 moves the electrode reaction assembly 6 above the second electrochemical reaction cell 3, and then the lower electrode reaction assembly 6 participates in the selective electrochemical lithium extraction operation in the second electrochemical reaction cell 3. At this time, the electrodes and electrolytic cells are symmetrically switched, and the above-mentioned anodic and cathodic reactions are carried out again when energized, so as to further enrich lithium ions in the electrolyte in the anodic region.

[0052] 5. Secondary Cleaning and Drying: After the lithium extraction time in the second electrochemical reaction cell 3 is reached, the mobile lifting vehicle 5 raises the electrode reaction assembly 6 and suspends it for several minutes until it stops dripping. Then, the mobile lifting vehicle 5 moves the electrode reaction assembly 6 to the second cleaning cell 9, and then lowers the electrode reaction assembly 6 into the second cleaning cell 9 for ultrasonic cleaning for several minutes before raising it again. The mobile lifting vehicle 5 moves the electrode reaction assembly 6 above the drying cell 8, and then lowers the electrode reaction assembly 6 into the drying cell 8 for drying for several minutes before raising it again, completing the cleaning and drying process after the secondary lithium extraction.

[0053] 6. Lithium Extraction in Cycle: After secondary cleaning and drying, the mobile lifting vehicle 5 moves the electrode reaction assembly 6 back above the first electrochemical reaction cell 2, ready for the next round of lithium extraction. Following steps 1 to 5 above, lithium extraction occurs immediately upon power-on, continuously transferring lithium ions from the oilfield wastewater to the electrolyte at the anode, achieving efficient enrichment and extraction of lithium ions, and realizing precise lithium extraction from oilfield wastewater.

[0054] The solution circulation system also includes an oilfield wastewater supply tank 11 for holding filtered crude purified oilfield wastewater, a water supply tank 12 for holding cleaning water, a wastewater collection tank 13 for holding wastewater after lithium extraction from oilfield wastewater, an anolyte storage tank 14 for holding anolyte, and a wastewater tank 15 for holding cleaning wastewater. Deionized water or distilled water is used in the water supply tank 12 to ensure cleaning effectiveness.

[0055] Electrolyte circulation: The anolyte in the anolyte storage tank 14 is transported to the anode of the first electrochemical reaction tank 2 and the anode of the second electrochemical reaction tank 3 via the first delivery pipeline assembly 17. The lithium-ion-enriched anolyte is then returned to the anolyte storage tank 14 for recycling. Once the lithium-ion concentration in the anolyte reaches a set value, the anolyte in the anolyte storage tank 14 is recovered and replaced.

[0056] Waste liquid treatment: After lithium extraction, the cathode oilfield waste liquid is discharged into the waste liquid collection pool 13. After the discharge is completed, the oilfield waste liquid supply pool 11 supplies new oilfield waste liquid to the cathode of the first electrochemical reaction pool 2 or the cathode of the second electrochemical reaction pool 3 to continue the lithium extraction operation.

[0057] The electrode reaction assembly 6 switches back and forth between the first electrochemical reaction cell 2 and the second electrochemical reaction cell 3 to achieve a bidirectional transport mechanism of "lithium extraction upon energization": Electrode assembly 6 alternately plays the role of "lithium-ion transporter" in the two electrochemical reaction cells: First stage: In the cathode region of the first electrochemical reaction cell 2, iron phosphate (FePO4) captures lithium ions (Li) from waste oil through a reduction reaction. + This process generates lithium iron phosphate (LiFePO4), enabling the fixation of lithium ions from waste oil into cathode materials.

[0058] Second stage: When switching to the anode region of the second electrochemical reaction cell 3, lithium iron phosphate (LiFePO4) is oxidized, releasing lithium ions (Li... + The lithium ions are transferred from the cathode material to the electrolyte and then into the anode electrolyte.

[0059] Reverse cycle: Similarly, the electrode reaction assembly 6 fixes lithium ions again in the cathode region of the second electrochemical reaction cell 3, and switches back to the anode region of the first electrochemical reaction cell 2 to release lithium ions, forming a closed-loop migration path.

[0060] Effect: Lithium ions are continuously and directionally "transported" from waste oil to the anolyte, and finally enriched in the anolyte storage pool 14, realizing the continuous lithium extraction process and avoiding the downtime losses of traditional intermittent operation.

[0061] Dynamically balancing electrode reactions improves energy efficiency and material stability. Reciprocating switching, through alternating insertion / extraction reactions, keeps the electrode material in a dynamic equilibrium state, slowing capacity decay and extending lifespan. Reciprocating switching, by changing the direction of the electrode reaction (e.g., cathode → anode), periodically perturbs the electric double layer on the electrode surface, reducing polarization accumulation, maintaining low overpotential, and improving energy efficiency.

[0062] The first electrochemical reaction cell 2 and the second electrochemical reaction cell 3 can independently adjust the electrolyte composition to meet the needs of different reaction stages. This separate-cell design avoids cross-contamination of the electrolyte while simultaneously increasing the driving force for lithium-ion migration and reducing ineffective recycling. The modular design of the electrode reaction assembly 6 allows for easy expansion of the processing scale by increasing the number of electrochemical reaction cells or parallel units, meeting industrial-grade lithium extraction requirements. After lithium ions are efficiently enriched in the anolyte, the lithium content in the remaining waste oil is significantly reduced, allowing for further reuse in oilfield operations or simple treatment before discharge, reducing environmental pollution. The lithium-rich solution in the anolyte storage cell 14 can be processed through subsequent processes (such as precipitation and extraction) to extract high-purity lithium salts, while the lithium-poor electrolyte can be recycled back to the electrochemical reaction cell, forming a closed-loop resource system. The reciprocating switching design of the electrode reaction assembly 6 achieves a highly efficient, stable, and sustainable "lithium extraction upon power-up" process through five mechanisms: directional lithium-ion migration, dynamic electrode balance, separate electrolyte cell control, modular expansion, and closed-loop resource utilization. This innovative model not only breaks through the efficiency bottleneck of traditional intermittent lithium extraction, but also provides a technological paradigm for the industrial recycling of low-grade lithium resources such as oilfield waste liquid.

[0063] The first electrochemical reaction cell 2 includes an anode reaction cell housing 201, an anion exchange membrane 203, gaskets, and a cathode reaction cell housing 202, all connected as a single unit by bolts and nuts. The lower end of the anode reaction cell housing 201 is fixed to the upper surface of the support platform 1. The anode reaction cell housing 201 has a row of anode electrolytic cells 2011 with side and top openings for accommodating the anolyte. The cathode reaction cell housing 202 has a row of cathode electrolytic cells 2021 with side and top openings for accommodating oilfield waste liquid. Each pair of anode electrolytic cells 2011 and cathode electrolytic cells 2021 in the first electrochemical reaction cell 2 is separated by an anion exchange membrane 203, allowing only anions to pass through and preventing mixing of the anode and cathode electrolytes.

[0064] The anolyte 2011 has a first inlet / outlet port 2012 and a first overflow port 2013. A row of first inlet / outlet ports 2012 communicates with the anolyte storage tank 14 via a first conveying pipeline assembly 17. The first conveying pipeline assembly 17 includes a first metering pump 171 installed on the anolyte storage tank 14 to draw liquid from it, and a first integrated pipeline 172 connecting the row of first inlet / outlet ports 2012 to the anolyte storage tank 14. A first solenoid valve 173 is installed on a branch connecting the first integrated pipeline 172 to the first metering pump 171. A second solenoid valve 174 is installed on a branch directly communicating with the anolyte storage tank 14, enabling precise control of the electrolyte and the recycling and enrichment of lithium ions. A row of first overflow ports 2013 communicates with the anolyte storage tank 14 via a first overflow pipeline 18.

[0065] The cathode electrolytic cell 2021 has a second inlet / outlet port 2022 and a second overflow port 2023. A row of second inlet / outlet ports 2022 connects to the oilfield waste liquid supply tank 11 and the waste liquid collection tank 13 via a second conveying pipeline assembly 19. The second conveying pipeline assembly 19 includes a second metering pump 191 installed on the oilfield waste liquid supply tank 11 and drawing liquid from it, and a second integrated pipeline 192 connecting the row of second inlet / outlet ports 2022, the oilfield waste liquid supply tank 11, and the waste liquid collection tank 13. A third solenoid valve 193 is installed on the branch pipe connecting the second integrated pipeline 192 to the second metering pump 191. A fourth solenoid valve 194 is installed on the branch pipe connecting the second integrated pipeline 192 to the waste liquid collection tank 13. A row of second overflow ports 2023 connects to the oilfield waste liquid supply tank 11 via a second overflow pipeline 20.

[0066] An anode contact 21, electrically connected to the anode reaction material of the electrode reaction assembly 6, is embedded in the upper end of the anode reaction tank housing 201. A cathode contact 22, electrically connected to the cathode reaction material of the electrode reaction assembly 6, is embedded in the upper end of the cathode reaction tank housing 202.

[0067] The structural features of the second electrochemical reaction tank 3 are symmetrically arranged with respect to the first electrochemical reaction tank 2 about the drying tank 8. The connection supply and discharge relationship between the second electrochemical reaction tank 3 and the oilfield waste liquid supply tank 11, the waste liquid collection tank 13, and the anode electrolyte storage tank 14 is the same as that of the first electrochemical reaction tank 2, and will not be described in detail here.

[0068] The hoisting frame 4 includes two gantry frames 41 fixed side-by-side on the support platform 1. The columns of the two gantry frames 41 are connected as one unit by multiple fixed crossbars. A pair of guide rails 42 are installed on the upper end of the two gantry frames 41, and limit baffles are provided at the ends of the guide rails 42. A rack 43 is installed on the upper end of one of the gantry frames 41. A first position detection sensor 31, a second position detection sensor 32, a third position detection sensor 33, a fourth position detection sensor 34, and a fifth position detection sensor 35 are sequentially installed on the side of the crossbeam of one of the gantry frames 41, corresponding to the positions of the first electrochemical reaction tank 2, the first cleaning tank 7, the drying tank 8, the second cleaning tank 9, and the second electrochemical reaction tank 3.

[0069] The mobile lifting vehicle 5 includes a horizontal frame 51. Two rows of sliders, linearly connected to a pair of guide rails 42, are installed below the horizontal frame 51. A linear electric cylinder 52 is vertically mounted on the horizontal frame 51. The lower end of the linear electric cylinder 52 extends through two gantry frames 41 and connects to the middle of the electrode reaction assembly 6. A servo motor 53 for horizontal movement is also mounted on the horizontal frame 51. A gear 54, cooperating with a rack 43, is mounted on the output shaft of the servo motor 53. A sixth position detection sensor 56 is mounted on one side of the horizontal frame 51 corresponding to the position of the electrode reaction assembly 6 via an L-shaped bracket 55. In this embodiment, the first position detection sensor 31, the second position detection sensor 32, the third position detection sensor 33, the fourth position detection sensor 34, the fifth position detection sensor 35, and the sixth position detection sensor 56 all employ through-beam photoelectric switches, with the sixth position detection sensor 56 serving as the receiver and the others as transmitters. The detection sensor settings ensure that the mobile lifting vehicle 5 can accurately move the electrode reaction assembly 6 to the positions of the first electrochemical reaction tank 2, the first cleaning tank 7, the drying tank 8, the second cleaning tank 9, or the second electrochemical reaction tank 3.

[0070] The electrode reaction assembly 6 includes a first conductive substrate 61 and a second conductive substrate 62 arranged side by side. The first conductive substrate 61 and the second conductive substrate 62 are fixed together by an inverted T-shaped insulating retainer 63, and the insulating retainer 63 has a first open channel 64 and a second open channel 65 respectively located below the first conductive substrate 61 and the second conductive substrate 62. The center distance between the first open channel 64 and the second open channel 65 is the same as the center distance between the anode and cathode electrolytic cells of the first electrochemical reaction cell 2, ensuring accurate electrode docking. External retainers 66 are installed on the side walls and the upper half of the insulating retainer 63 by several sets of bolts and nuts. A connecting plate 67 is provided at the upper middle part of the external retainer 66 to connect and cooperate with the telescopic end of the linear electric cylinder 52. Several sets of first conductive base rods 68 are arranged on the lower surface of the first conductive substrate 61 along the center line of the first open channel 64. The first conductive base rods 68 are coated with an anode lithium iron phosphate layer 69. Several sets of second conductive base rods 610 are arranged on the lower surface of the second conductive substrate 62 along the center line of the first open channel 64. The second conductive substrate 610 is coated with a cathode iron phosphate layer 611. The first conductive substrate 61 is conductive when it contacts the anode contact 21. The second conductive substrate 62 is conductive when it contacts the cathode contact 22.

[0071] The first cleaning tank 7 includes a rectangular trough 71 with an open top. A first partition 72 is provided in the middle of the rectangular trough 71. Ultrasonic generating devices 73 are installed on both side walls of the rectangular trough 71. Two water inlet pipes 74 are provided at one end of the rectangular trough 71. A third metering pump 75 is installed on the water supply tank 12, and the third metering pump 75 draws water from the water supply tank 12. The water inlet pipes 74 are connected to the outlet end of the third metering pump 75. Two water outlet pipes 76 are provided at the bottom of the other end of the rectangular trough 71, and two third overflow pipes 77 are provided in the upper part, with the ends of the third overflow pipes 77 connected to the water outlet pipes 76. A fifth solenoid valve 78 is installed on the direct connection section between the water outlet pipes 76 and the rectangular trough 71. The structural features of the second cleaning tank 9 are symmetrically arranged with respect to the drying tank 8, as are the structural features of the first cleaning tank 7.

[0072] The drying tank 8 has a drying groove 81 at its upper end. A guide channel 82, symmetrically arranged around the drying groove 81, is located at one end of the drying tank 8. A row of downward-sloping air-blowing channels 83 is formed in the wall between the guide channel 82 and the drying groove 81. The bottom of the drying groove 81 is lower than the bottom of the guide channel 82. The wall between the openings of the two guide channels 82 is configured as a splitting cone 84. The two guide channels 82 are connected to the air outlet of the hot air blower 10. A second partition 85 is provided in the middle of the drying groove 81.

[0073] A protective cover 16 is installed on the first cleaning tank 7, the drying tank 8, and the second cleaning tank 9. The upper end of the drying tank 8 is lower than the upper end of the first cleaning tank 7. The protective cover 16 includes two rectangular frames 161 that are fastened to the upper ends of the first cleaning tank 7 and the second cleaning tank 9. A protective baffle 162 is fixed to each of the two side walls along the length of the rectangular frames 161, and the lower end of the protective baffle 162 contacts the upper surface of the support platform 1. The two ends of the two rectangular frames 161 are connected as one unit by two fixed connecting rods 163. A pair of symmetrically arranged guide plates 164 are fixed between the two fixed connecting rods 163 and the two rectangular frames 161, with the lower end of the guide plates 164 extending to the upper edge of the drying groove 81. When the electrode reaction assembly 6 is removed from the water tank, it can be moved to the drying tank 8 with less waiting time. The water dripping during the movement flows into the drying groove 81 and evaporates under the action of subsequent hot air flow, reducing the cleaning time and increasing the overall energization time ratio.

[0074] In automated lithium extraction processes, the speed of electrode transfer and processing directly impacts overall work efficiency. If electrodes require prolonged natural drying after cleaning, it prolongs the processing cycle and reduces production efficiency. The drying tank 8 uses hot air generated by the hot air blower 10 to quickly remove moisture from the electrode surface, ensuring the electrodes remain dry before being incorporated into the electrochemical reaction and maintaining a stable electrolyte concentration. The rapid drying function of the drying tank 8 significantly shortens electrode processing time, improves overall work efficiency, and meets the demands of large-scale industrial production.

[0075] During the electrochemical reaction, impurities from oilfield wastewater, reaction products, and electrolyte residues adhere to the electrode surfaces in the first cleaning tank 7 and the second cleaning tank 9. If these impurities are not removed promptly, they will cover the electrode surface, hindering lithium ion insertion and extraction, thus reducing lithium extraction efficiency. The first cleaning tank 7 and the second cleaning tank 9 utilize ultrasonic cleaning technology. The impact force generated by the bursting of microbubbles produced by high-frequency vibration on the electrode surface effectively removes the deposits, restores the active surface area of ​​the electrode, and ensures the continuous and efficient conduct of the electrochemical reaction. During lithium extraction, the electrodes need to be used alternately in different electrolytic cells (such as the first electrochemical reaction cell 2 and the second electrochemical reaction cell 3). If the electrodes are not thoroughly cleaned, impurities or residual electrolyte from the previous electrolytic cell may be carried into the next, causing cross-contamination and affecting the purity of the extracted lithium. Cleaning in the first cleaning tank 7 and the second cleaning tank 9 ensures that the electrodes remain clean during transfer, avoids cross-contamination, and improves the purity of the extracted lithium product.

[0076] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0077] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A lithium extraction device for oilfield wastewater based on selective electrochemical technology, characterized in that: The system includes a support platform (1), a first electrochemical reaction cell (2) and a second electrochemical reaction cell (3) with electrodes and structures symmetrically arranged on the support platform (1), a hoisting frame (4) on the support platform (1), a mobile lifting vehicle (5) on the hoisting frame (4), an electrode reaction assembly (6) on the telescopic end of the mobile lifting vehicle (5), and a first cleaning tank (7), a drying tank (8), and a second cleaning tank (9) on the support platform (1) between the first electrochemical reaction cell (2) and the second electrochemical reaction cell (3); a hot air blower (10) is connected to the air inlet end of the drying tank (8). The electrode reaction assembly (6) participates in the electrochemical reaction for the first time in the first electrochemical reaction cell (2). The anode reaction material of the electrode reaction assembly (6) is initially lithium iron phosphate; the cathode reaction material of the electrode reaction assembly (6) is initially iron phosphate.

2. The oilfield wastewater lithium extraction device based on selective electrochemical technology according to claim 1, characterized in that, It also includes an oilfield waste liquid supply pool (11) for holding filtered crude purified oilfield waste liquid, a water supply pool (12) for holding cleaning water, a waste liquid collection pool (13) for holding waste liquid after lithium extraction from oilfield waste liquid, an anolyte storage pool (14) for holding anolyte, and a wastewater pool (15) for holding cleaning wastewater.

3. The oilfield wastewater lithium extraction device based on selective electrochemical technology according to claim 2, characterized in that, The first electrochemical reaction tank (2) includes an anode reaction tank shell (201), an anion exchange membrane separator (203), a gasket, and a cathode reaction tank shell (202) connected together by several bolts and nuts; the lower end of the anode reaction tank shell (201) is fixed to the upper surface of the support platform (1); the anode reaction tank shell (201) is provided with a row of anode electrolytic cells (2011) with side and top openings for accommodating anode electrolyte; the cathode reaction tank shell (202) is provided with a row of cathode electrolytic cells (2021) with side and top openings for accommodating oilfield waste liquid; each pair of anode electrolytic cells (2011) and cathode electrolytic cells (2021) in the first electrochemical reaction tank (2) are separated by an anion exchange membrane separator (203); The anolyte (2011) is provided with a first inlet / outlet hole (2012) and a first overflow hole (2013); a row of the first inlet / outlet holes (2012) is connected to the anolyte storage tank (14) through a first conveying pipe assembly (17); a row of the first overflow holes (2013) is connected to the anolyte storage tank (14) through a first overflow pipe (18); The cathode electrolytic cell (2021) is provided with a second inlet / outlet hole (2022) and a second overflow hole (2023); a row of second inlet / outlet holes (2022) is connected to the oilfield waste liquid supply pool (11) and the waste liquid collection pool (13) through a second conveying pipeline assembly (19); a row of second overflow holes (2023) is connected to the oilfield waste liquid supply pool (11) through a second overflow pipe (20); An anode contact (21) electrically connected to the anode reaction material of the electrode reaction assembly (6) is embedded in the upper end of the anode reaction tank housing (201); a cathode contact (22) electrically connected to the cathode reaction material of the electrode reaction assembly (6) is embedded in the upper end of the cathode reaction tank housing (202).

4. The oilfield wastewater lithium extraction device based on selective electrochemical technology according to claim 3, characterized in that, The first delivery pipeline assembly (17) includes a first metering pump (171) installed on the anolyte storage tank (14) and drawing liquid from the anolyte storage tank (14), and a first integrated pipeline (172) connecting a row of first inlet and outlet holes (2012) to the anolyte storage tank (14); a first solenoid valve (173) is installed on the branch pipe connecting the first integrated pipeline (172) to the first metering pump (171); a second solenoid valve (174) is installed on the branch pipe directly connecting the first integrated pipeline (172) to the anolyte storage tank (14). The second delivery pipeline assembly (19) includes a second metering pump (191) installed on the oilfield waste liquid supply pool (11) and drawing liquid from the oilfield waste liquid supply pool (11), and a second integrated pipeline (192) connecting a row of second inlet and outlet holes (2022), the oilfield waste liquid supply pool (11) and the waste liquid collection pool (13); a third solenoid valve (193) is installed on the branch pipe connecting the second integrated pipeline (192) and the second metering pump (191); a fourth solenoid valve (194) is installed on the branch pipe connecting the second integrated pipeline (192) and the waste liquid collection pool (13). The structural features of the second electrochemical reaction tank (3) are symmetrically arranged with respect to the structural features of the first electrochemical reaction tank (2) about the drying tank (8).

5. The oilfield wastewater lithium extraction device based on selective electrochemical technology according to claim 4, characterized in that, The hoisting frame (4) includes two gantry frames (41) fixed on the support platform (1) and arranged side by side; the columns of the two gantry frames (41) are connected as one unit by multiple fixed crossbars; a pair of guide rails (42) are installed on the upper end of the two gantry frames (41), and a limit baffle is provided at the end of the guide rails (42); a rack (43) is installed on the upper end of one of the gantry frames (41); a first position detection sensor (31), a second position detection sensor (32), a third position detection sensor (33), a fourth position detection sensor (34) and a fifth position detection sensor (35) are installed on the side of the crossbeam of one of the gantry frames (41) in sequence, corresponding to the positions of the first electrochemical reaction tank (2), the first cleaning tank (7), the drying tank (8), the second cleaning tank (9) and the second electrochemical reaction tank (3).

6. The oilfield wastewater lithium extraction device based on selective electrochemical technology according to claim 5, characterized in that, The mobile lifting vehicle (5) includes a horizontal frame (51); two rows of sliders are installed below the horizontal frame (51) and are linearly connected to a pair of guide rails (42); a linear electric cylinder (52) is vertically installed on the horizontal frame (51); the lower end of the linear electric cylinder (52) extends through the two gantry frames (41) and is connected to the middle of the electrode reaction assembly (6); a servo motor (53) for horizontal movement drive is also installed on the horizontal frame (51); a gear (54) that cooperates with the rack (43) is installed on the output shaft of the servo motor (53); a sixth position detection sensor (56) is installed on one side of the horizontal frame (51) corresponding to the position of the electrode reaction assembly (6) through an L-shaped bracket (55).

7. The oilfield wastewater lithium extraction device based on selective electrochemical technology according to claim 6, characterized in that, The electrode reaction assembly (6) includes a first conductive substrate (61) and a second conductive substrate (62) arranged side by side; the first conductive substrate (61) and the second conductive substrate (62) are fixed together by an inverted T-shaped insulating retainer (63), and the insulating retainer (63) is located below the first conductive substrate (61) and the second conductive substrate (62) respectively, with a first open channel (64) and a second open channel (65); the center distance between the first open channel (64) and the second open channel (65) is the same as the center distance between the anode and cathode electrolytic cells of the first electrochemical reaction cell (2); the side walls and the upper half of the insulating retainer (63) are fitted with an external retainer (66) by a number of bolts and nuts; the external retainer (66) A connecting plate (67) is provided at the middle of the upper end of the retainer (66) to connect and cooperate with the telescopic end of the linear electric cylinder (52); a plurality of first conductive base rods (68) are provided on the lower surface of the first conductive substrate (61) along the center line of the first open channel (64); an anode lithium iron phosphate layer (69) is laminated on the outside of the first conductive base rods (68); a plurality of second conductive base rods (610) are provided on the lower surface of the second conductive substrate (62) along the center line of the first open channel (64); a cathode iron phosphate layer (611) is laminated on the outside of the second conductive base rods (610); the first conductive substrate (61) is conductive when in contact with the anode contact (21); the second conductive substrate (62) is conductive when in contact with the cathode contact (22).

8. The oilfield wastewater lithium extraction device based on selective electrochemical technology according to claim 1, characterized in that, The first cleaning tank (7) includes a rectangular trough (71) with an upper opening; a first partition (72) is provided in the middle of the rectangular trough (71); ultrasonic generators (73) are installed on both side walls of the rectangular trough (71); two water inlet pipes (74) are provided at one end of the rectangular trough (71); a third metering pump (75) is installed on the water supply tank (12), and the third metering pump (75) draws water from the water supply tank (12); the water inlet pipes (74) and the third metering pump (75) are connected to the water supply tank (12). The pump (75) is connected to the outlet end; two outlet pipes (76) are provided at the bottom of the other end of the rectangular tank (71), and two third overflow pipes (77) are provided in the upper part, and the end of the third overflow pipe (77) is connected to the outlet pipe (76); a fifth solenoid valve (78) is installed on the direct connection pipe section between the outlet pipe (76) and the rectangular tank (71); the structural features of the second cleaning tank (9) and the structural features of the first cleaning tank (7) are symmetrically arranged with respect to the air drying tank (8).

9. The oilfield wastewater lithium extraction device based on selective electrochemical technology according to claim 8, characterized in that, The drying tank (8) has a drying groove (81) at its upper end; one end of the drying tank (8) has a guide channel (82) symmetrically arranged with respect to the drying groove (81); a row of downwardly arranged blowing channels (83) is opened in the wall between the guide channel (82) and the drying groove (81); the bottom of the drying groove (81) is lower than the bottom of the guide channel (82); the wall between the opening ends of the two guide channels (82) is set as a gas-distributing cone (84); the two guide channels (82) are connected to the air outlet of the hot air blower (10); a second partition (85) is provided in the middle of the drying groove (81).

10. The oilfield wastewater lithium extraction device based on selective electrochemical technology according to claim 9, characterized in that, A protective cover (16) is installed on the first cleaning pool (7), the drying pool (8), and the second cleaning pool (9); the upper end of the drying pool (8) is lower than the upper end of the first cleaning pool (7); the protective cover (16) includes two rectangular frames (161) that are fastened to the upper ends of the first cleaning pool (7) and the second cleaning pool (9); a protective baffle (162) is fixed on each of the two side walls of the rectangular frame (161) along its length, and the lower end of the protective baffle (162) is in contact with the upper surface of the support platform (1); the two ends of the two rectangular frames (161) are connected as one unit by two fixed connecting rods (163); a pair of symmetrically arranged guide plates (164) are fixed between the two fixed connecting rods (163) and the two rectangular frames (161), and the lower end of the guide plate (164) extends to the upper edge of the drying groove (81).

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