A system and method for removing oil from a spent lithium battery stripping solution

Abstract

The application relates to a waste lithium battery stripping solution oil removal and recovery system and method, and belongs to the technical field of waste lithium battery resource recovery, which comprises a stripping solution receiving unit for receiving stripping solution from an extraction process and stabilizing the flow of the stripping solution; a ceramic membrane cross-flow separation unit for separating the stripping solution into concentrated liquid rich in organic phase and water phase permeate liquid from which oil has been removed; a membrane cleaning unit for periodically or on-demand cleaning of the ceramic membrane cross-flow separation unit to restore the membrane flux; an organic phase recovery unit, and a cooperative control unit; wherein the units are sequentially connected through pipelines, valves and pumping equipment. The waste lithium battery stripping solution oil removal and recovery system and method adopt the ceramic membrane cross-flow separation technology, utilize the hydrophilic and oleophobic characteristics and nanoscale pore size to intercept the organic phase, the oil removal rate can reach more than 99%, the oil content of the stripping solution is reduced to below 5 mg / L, the TOC is below 30 mg / L, the purity of the subsequent metal salt product is ensured, and the battery grade standard is met.

Description

Technical Field

[0001] This invention relates to the field of waste lithium battery resource recycling technology, specifically to the field of hydrometallurgy and solvent extraction post-processing technology of waste lithium battery cathode materials. Background Technology

[0002] The recovery of valuable metals (such as nickel, cobalt, manganese, and lithium) from spent lithium-ion battery cathode materials typically employs solvent extraction for separation and purification. However, in actual production, due to intense contact between the back-extraction solution and the organic phase, and insufficient phase separation time, the back-extraction solution often contains organic phases (such as extractants P204 and P507, and sulfonated kerosene). This results in significant extractant loss, making subsequent metal salt products susceptible to organic contamination, affecting product quality, and increasing the difficulty of wastewater treatment.

[0003] Currently, common oil removal methods mainly include activated carbon adsorption and resin adsorption. While these methods have a certain oil removal effect, they have the following significant drawbacks:

[0004] 1. It generates a large amount of waste activated carbon or waste resin, forming secondary solid waste, which has high treatment costs and great environmental pressure;

[0005] 2. The adsorbent material is easily saturated and needs to be replaced frequently, making operation and maintenance complex;

[0006] 3. The extractant cannot be recycled and reused, resulting in serious waste of resources;

[0007] 4. Poor process continuity and low degree of automation make it difficult to adapt to the needs of large-scale industrial production.

[0008] Therefore, there is an urgent need for an efficient, environmentally friendly, and recyclable back-extraction liquid oil removal technology to solve the problems of waste residue pollution, extractant waste, and unstable product quality caused by traditional methods. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides an oil removal and recycling system and method for waste lithium battery back-extraction liquid. It has the advantages of high oil removal efficiency, green and waste-free operation, recyclable and reusable extractant, and high process integration. It effectively solves the problems of secondary solid waste pollution, serious extractant loss, complex process flow and high operating cost of existing oil removal technologies.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] An oil removal and recovery system for waste lithium battery stripping solution includes:

[0012] The back-extraction liquid receiving unit is used to receive the back-extraction liquid from the extraction process and stabilize its flow rate. Its core includes a back-extraction liquid buffer tank.

[0013] A ceramic membrane cross-flow separation unit is connected to the output end of the back-extraction liquid receiving unit and is used to separate the back-extraction liquid into a concentrated liquid enriched with organic phase and an oil-free aqueous phase permeate. Its core includes a membrane assembly composed of hydrophilic and oleophobic ceramic membrane elements.

[0014] A membrane cleaning unit, which can be switched to the ceramic membrane cross-flow separation unit, is used to periodically or as needed clean the ceramic membrane cross-flow separation unit to restore its membrane flux.

[0015] An organic phase recovery unit is connected to the concentrated liquid output end of the ceramic membrane cross-flow separation unit. It is used to purify and recover the organic phase in the concentrated liquid and return the recovered organic phase to the extraction process for reuse.

[0016] And a collaborative control unit, which is connected to the back-extraction liquid receiving unit, the ceramic membrane cross-flow separation unit, the membrane cleaning unit and the organic phase recovery unit respectively, to coordinate the operating parameters and start-up / stop sequence of each unit and realize the automated control of the whole system;

[0017] The aforementioned units are connected in series via pipes, valves, and pumping equipment to form a closed-loop circulation system from oil removal from the back-extraction solution to organic phase recovery.

[0018] Furthermore, the ceramic membrane cross-flow separation unit includes a feed pump, a ceramic membrane module, a permeate storage tank, and a concentrate storage tank; the ceramic membrane module is filled with a hydrophilic and oleophobic ceramic membrane element with a pore size of 50-200 nm and is made of α-alumina or zirconium oxide.

[0019] The ceramic membrane module is provided with a feed inlet, a permeate outlet and a concentrate outlet, and the feed pump is connected to the feed inlet through a feed pipe.

[0020] Furthermore, the ceramic membrane module adopts a cross-flow filtration structure, and the feed pipe is equipped with a pressure sensor and a flow regulating valve to regulate the operating pressure to 0.1-0.3MPa and the membrane surface flow velocity to 1-3m / s.

[0021] Furthermore, the membrane cleaning unit includes a cleaning solution storage tank, a cleaning pump, and a waste liquid collection tank; the cleaning solution storage tank is equipped with a deionized water chamber and an acid-base cleaning solution chamber, wherein the acid-base cleaning solution is a 0.5%-1% dilute sulfuric acid or sodium hydroxide solution.

[0022] Furthermore, the organic phase recovery unit includes a distillation column, a condenser, and an extractant storage tank; the operating parameters of the distillation column are: top temperature 120-150℃, bottom temperature 180-220℃, and operating pressure 0.05-0.1MPa.

[0023] Furthermore, the collaborative control unit is a PLC control system used to realize dynamic adjustment of the back-extraction liquid flow rate, control of membrane separation parameters, automatic start and stop of the cleaning program, and automated control of the distillation process.

[0024] Another technical problem to be solved by the present invention is to provide a method for oil removal and recovery of waste lithium battery back-extraction solution, comprising the following steps:

[0025] S1: The back-extraction solution is introduced into the buffer tank, and after the flow rate is stabilized, it is sent to the ceramic membrane cross-flow separation unit;

[0026] S2: Under pressure, cross-flow separation is performed using a ceramic membrane to collect the permeate and concentrate;

[0027] S3: When the membrane flux decreases by more than 30%, initiate the membrane cleaning and regeneration process;

[0028] S4: The concentrate is sent to a distillation column to recover the extractant;

[0029] S5: The permeate enters the subsequent metal purification process.

[0030] Furthermore, in step S2, the separation temperature is 30-50℃, and the volume of the concentrated liquid is 1 / 10-1 / 20 of the original extraction liquid volume.

[0031] Furthermore, in step S3, the cleaning and regeneration process includes backwashing with deionized water for 10-15 minutes, circulating cleaning with dilute acid or alkali solution for 30 minutes, and then rinsing with deionized water until neutral.

[0032] Furthermore, in step S5, the oil content of the permeate is less than 5 mg / L and the TOC is less than 30 mg / L, so it can be directly used to prepare battery-grade metal salt products.

[0033] Compared with the prior art, the present invention provides an oil removal and recovery system and method for waste lithium battery back-extraction liquid, which has the following beneficial effects:

[0034] 1. The oil removal and recovery system and method for waste lithium battery back-extraction liquid adopts ceramic membrane cross-flow separation technology, which utilizes its hydrophilic and oleophobic properties and nanoscale pore size to retain organic phase. The oil removal rate can reach more than 99%, and the oil content of the back-extraction liquid is reduced to below 5 mg / L and TOC is below 30 mg / L. This ensures the purity of subsequent metal salt products and meets battery-grade standards, achieving the advantages of efficient oil removal and improved product quality.

[0035] 2. The oil removal and recycling system and method for the back-extraction liquid of waste lithium batteries does not use consumables such as activated carbon and resin throughout the process, and only generates a small amount of treatable cleaning waste liquid, which greatly reduces the amount of hazardous waste generated and the treatment cost. It is in line with the policy orientation of green manufacturing and carbon neutrality, and achieves the advantages of being green and environmentally friendly with no waste residue generated.

[0036] 3. The oil removal and recovery system and method for waste lithium battery back-extraction liquid achieves efficient recovery and recycling of the extractant by enriching the organic phase with a ceramic membrane and combining it with distillation recovery. The recovery rate can reach more than 99%, which significantly reduces the purchase cost of the extractant and achieves the advantages of resource recycling and reduced production costs.

[0037] 4. The oil removal and recovery system and method for waste lithium battery back-extraction liquid adopts PLC full-process automated control, with simple and compact process, convenient membrane cleaning and regeneration, high flux recovery rate, long equipment life (3-5 years), low maintenance cost, and is suitable for continuous industrial production.

[0038] 5. The oil removal and recovery system and method for waste lithium battery back-extraction liquid is applicable not only to oil removal from waste lithium battery back-extraction liquid, but can also be extended to the purification treatment of aqueous solutions containing organic phases in other fields such as hydrometallurgy and chemical separation. It has good industry versatility and promotion value. Attached Figure Description

[0039] Figure 1 This is a system block diagram of an oil removal and recovery system for back-extraction liquid from waste lithium batteries according to the present invention.

[0040] Figure 2 This is a process flow diagram of a method for oil removal and recovery of back-extraction liquid from waste lithium batteries according to the present invention. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Example 1:

[0043] This embodiment provides an oil removal and recovery system for waste lithium battery back-extraction solution, such as... Figure 1 As shown, it mainly includes the following five functional units, which are physically connected through pipes, valves and pumping equipment, and achieve signal connection and coordinated operation through a control system:

[0044] The core equipment of this unit is the back-extraction buffer tank. Its inlet is directly connected to the back-extraction outlet of the upstream extraction process via a pipeline, used to receive and temporarily store the back-extraction containing entrained organic phases (such as extractants P204 and P507 and diluent sulfonated kerosene). The buffer tank is equipped with a level sensor to monitor the liquid level in real time and transmit the signal to the co-control unit. The co-control unit controls the opening and closing of the buffer tank outlet valve according to a preset liquid level range (e.g., 60%-80% of the tank volume), thereby stably supplying back-extraction to subsequent units and avoiding the impact of flow fluctuations on the membrane separation process. The outlet of the buffer tank is connected to the next unit via a feed pipeline.

[0045] Ceramic membrane cross-flow separation unit: This unit is the core for achieving efficient oil-water separation. It includes a feed pump, ceramic membrane module, permeate storage tank, and concentrate storage tank.

[0046] Ceramic membrane module: Internally filled with a hydrophilic and oleophobic ceramic membrane element. In a preferred embodiment, the membrane material is α-alumina or zirconium oxide, and the pore size is controlled within 50-200 nm. This pore size range effectively traps oil droplets and large organic molecules, while allowing the aqueous phase and dissolved metal ions (such as Ni²⁺, Co²⁺, Mn²⁺) to pass through smoothly. The membrane module employs a cross-flow filtration structure and is equipped with a feed inlet, a permeate outlet, and a concentrate outlet.

[0047] Feed pump: Connected to the feed port of the ceramic membrane module through the feed pipe, it provides pressure drive for the separation process.

[0048] Parameter control: A pressure sensor and a flow regulating valve are installed on the feed pipeline. Based on sensor feedback, the co-control unit adjusts the feed pump frequency and the opening of the flow regulating valve to precisely control the operating pressure within 0.1-0.3 MPa and the membrane surface flow velocity within 1-3 m / s. The separation temperature is maintained within an optimal range of 30-50℃ through pipeline insulation or heat exchange devices.

[0049] Product collection: Under pressure, the purified aqueous phase (i.e., permeate) flows out from the permeate outlet and is collected in the permeate storage tank; the trapped and enriched oil phase (i.e., concentrate) is discharged from the concentrate outlet and collected in the concentrate storage tank.

[0050] Membrane cleaning unit: Used to clean and regenerate the membrane module when the flux of the ceramic membrane decreases (e.g., the flux decreases by more than 30% of the initial value) to restore its separation performance. This unit includes a cleaning solution storage tank, a cleaning pump, and a waste liquid collection tank.

[0051] Cleaning solution storage tank: Internally divided into two chambers, storing deionized water and 0.5%-1% dilute sulfuric acid or sodium hydroxide solution respectively, for step-by-step cleaning of different contaminants.

[0052] During cleaning, by switching valves, the cleaning fluid is circulated or backwashed to clean the ceramic membrane module under the drive of the cleaning pump. The waste liquid generated during cleaning is discharged into the waste liquid collection tank for unified treatment.

[0053] Organic phase recovery unit: Used for the resource recovery of enriched organic phases. This unit includes a distillation column, a condenser, and an extractant storage tank.

[0054] Distillation column: Its inlet is connected to the outlet of the concentrate storage tank. In a preferred embodiment, the distillation operating parameters are set as follows: top temperature 120-150°C, bottom temperature 180-220°C, and operating pressure 0.05-0.1 MPa. Under these conditions, the extractant and diluent in the organic phase are effectively separated and purified.

[0055] Condenser: Located at the top of the distillation column, used to condense and purify the organic vapors.

[0056] Extractant storage tank: Connected to the condenser outlet, it is used to collect the condensed high-purity extractant and diluent mixture, which can be returned to the upstream extraction process for direct reuse. Small amounts of heavy component impurities remaining at the bottom of the distillation column are periodically discharged for centralized, harmless treatment.

[0057] Collaborative Control Unit: In a preferred embodiment, a PLC control system is used as the core of the collaborative control unit. The PLC receives sensor signals (such as liquid level, pressure, flow rate, temperature, etc.) from each unit and realizes automated control of the entire system through a pre-written control program, including: dynamic adjustment of the back-extraction liquid feed, precise control of ceramic membrane separation operating parameters, automatic start-up, shutdown and switching of the membrane cleaning program, and temperature and pressure control of the distillation process, etc.

[0058] Example 2:

[0059] This embodiment provides a method for oil removal and recovery of back-extraction solution from waste lithium batteries, such as... Figure 2 As shown, the method for oil removal and recycling of waste lithium battery back-extraction solution applied to the above system includes the following steps:

[0060] Step S1: Collection and Stabilization of Back-extraction Solution

[0061] The back-extraction solution (mainly containing valuable metal salts such as nickel sulfate, cobalt sulfate, and manganese sulfate, as well as entrained organic phases) obtained from the leaching solution of waste lithium battery cathode materials through extraction and back-extraction is continuously introduced into the back-extraction solution buffer tank. The co-control unit automatically adjusts the outlet valve based on the liquid level sensor signal to maintain a stable flow rate to the ceramic membrane unit.

[0062] Step S2: Ceramic membrane cross-flow separation

[0063] Start the feed pump to pump the stripping solution into the ceramic membrane module. Under the regulation of the co-control unit, the system maintains cross-flow filtration at an operating pressure of 0.2 MPa (example value), a membrane surface velocity of 2 m / s (example value), and a temperature of 40°C (example value). The aqueous phase and dissolved metal salts become the permeate and enter the permeate storage tank; the oil phase is retained by the membrane and gradually accumulates in the concentrate. Separation continues until the volume of the concentrate is approximately 1 / 15 of the original stripping solution volume (example value), at which point the feed is stopped, and all the concentrate is discharged into the concentrate storage tank.

[0064] Step S3: Membrane cleaning and regeneration (as needed)

[0065] When the system detects a flux drop of more than 30% in the ceramic membrane module, or according to a predetermined cycle, the cleaning procedure is automatically initiated. First, the membrane module is backflushed with deionized water for 10-15 minutes to remove loose surface contaminants. Then, a 0.8% dilute sulfuric acid solution (or sodium hydroxide solution if the contaminants are alkaline or metal saponifies) is used for 30 minutes of circulating cleaning to dissolve and remove stubborn contaminants inside and on the membrane pores. Finally, the module is rinsed with deionized water for 5-10 minutes until the pH of the rinsing solution is neutral. All cleaning wastewater is discharged into a wastewater collection tank. After cleaning, the membrane flux can recover to more than 95% of its initial value.

[0066] Step S4: Organic phase recovery and reuse

[0067] The concentrated organic phase from the concentrate storage tank is pumped into the distillation column. The control system stabilizes the column's operating parameters at a top temperature of 135°C, a bottom temperature of 200°C, and a pressure of 0.08 MPa (example values). Under these conditions, the extractant (e.g., P507) and sulfonated kerosene are effectively separated and purified. The vapor, after condensation, is collected as the recovered organic phase in the extractant storage tank and can be directly reused in the extraction process, achieving closed-loop utilization. A small amount of residue at the bottom of the column is treated as hazardous waste and entrusted to a qualified unit for disposal.

[0068] Step S5: Subsequent product preparation

[0069] The back-extraction liquid collected from the liquid storage tank after oil removal was tested and found to have an oil content consistently below 5 mg / L and a total organic carbon (TOC) content below 30 mg / L, fully meeting the requirements for the preparation of battery-grade metal salts. This purified liquid can be directly transported to subsequent purification processes such as MVR evaporation and crystallization, and chemical precipitation, for the preparation of high-purity battery-grade products such as nickel sulfate and cobalt sulfate.

[0070] In summary:

[0071] The implementation of the above system and methods can achieve the following beneficial effects:

[0072] 1. It achieves efficient removal of organic phase from the back-extraction solution (oil removal rate >99%), ensuring the purity of subsequent metal products.

[0073] 2. The entire process does not generate any solid hazardous waste such as waste activated carbon, and only generates a small amount of easily treatable cleaning waste liquid, making it environmentally friendly.

[0074] 3. It achieves efficient recovery (recovery rate >99%) and recycling of the extractant, significantly reducing production costs.

[0075] 4. The system has a high degree of integration, is automated, and has a stable and reliable process, making it suitable for continuous industrial production.

[0076] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0077] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An oil removal and recovery system for waste lithium battery back-extraction solution, characterized in that, include: The back-extraction liquid receiving unit is used to receive the back-extraction liquid from the extraction process and stabilize its flow rate. Its core includes a back-extraction liquid buffer tank. A ceramic membrane cross-flow separation unit is connected to the output end of the back-extraction liquid receiving unit and is used to separate the back-extraction liquid into a concentrated liquid enriched with organic phase and an oil-free aqueous phase permeate. Its core includes a membrane assembly composed of hydrophilic and oleophobic ceramic membrane elements. A membrane cleaning unit, which can be switched to the ceramic membrane cross-flow separation unit, is used to periodically or as needed clean the ceramic membrane cross-flow separation unit to restore its membrane flux. An organic phase recovery unit is connected to the concentrated liquid output end of the ceramic membrane cross-flow separation unit. It is used to purify and recover the organic phase in the concentrated liquid and return the recovered organic phase to the extraction process for reuse. And a collaborative control unit, which is connected to the back-extraction liquid receiving unit, the ceramic membrane cross-flow separation unit, the membrane cleaning unit and the organic phase recovery unit respectively, to coordinate the operating parameters and start-up / stop sequence of each unit and realize the automated control of the whole system; The aforementioned units are connected in series via pipes, valves, and pumping equipment to form a closed-loop circulation system from oil removal from the back-extraction solution to organic phase recovery.

2. The oil removal and recovery system for waste lithium battery back-extraction solution according to claim 1, characterized in that, The ceramic membrane cross-flow separation unit includes a feed pump, a ceramic membrane module, a permeate storage tank, and a concentrate storage tank; the ceramic membrane module is filled with a hydrophilic and oleophobic ceramic membrane element with a pore size of 50-200nm and is made of α-alumina or zirconium oxide. The ceramic membrane module is provided with a feed inlet, a permeate outlet and a concentrate outlet, and the feed pump is connected to the feed inlet through a feed pipe.

3. The oil removal and recovery system for waste lithium battery back-extraction solution according to claim 2, characterized in that, The ceramic membrane module adopts a cross-flow filtration structure. The feed pipe is equipped with a pressure sensor and a flow regulating valve to regulate the operating pressure to 0.1-0.3MPa and the membrane surface flow velocity to 1-3m / s.

4. The oil removal and recovery system for waste lithium battery back-extraction solution according to claim 1, characterized in that, The membrane cleaning unit includes a cleaning solution storage tank, a cleaning pump, and a waste liquid collection tank; the cleaning solution storage tank is equipped with a deionized water chamber and an acid-base cleaning solution chamber, wherein the acid-base cleaning solution is a 0.5%-1% dilute sulfuric acid or sodium hydroxide solution.

5. The oil removal and recovery system for waste lithium battery back-extraction solution according to claim 1, characterized in that, The organic phase recovery unit includes a distillation column, a condenser, and an extractant storage tank; the operating parameters of the distillation column are: top temperature 120-150℃, bottom temperature 180-220℃, and operating pressure 0.05-0.1MPa.

6. The oil removal and recovery system for waste lithium battery back-extraction solution according to claim 1, characterized in that, The collaborative control unit is a PLC control system used to realize dynamic adjustment of the back-extraction liquid flow rate, control of membrane separation parameters, automatic start and stop of the cleaning program, and automated control of the distillation process.

7. A method for oil removal and recovery of waste lithium battery stripping solution, applied to the oil removal and recovery system for waste lithium battery stripping solution as described in any one of claims 1-6, characterized in that, Includes the following steps: S1: The back-extraction solution is introduced into the buffer tank, and after the flow rate is stabilized, it is sent to the ceramic membrane cross-flow separation unit; S2: Under pressure, cross-flow separation is performed using a ceramic membrane to collect the permeate and concentrate; S3: When the membrane flux decreases by more than 30%, initiate the membrane cleaning and regeneration process; S4: The concentrate is sent to a distillation column to recover the extractant; S5: The permeate enters the subsequent metal purification process.

8. The method for oil removal and recovery of waste lithium battery back-extraction solution according to claim 7, characterized in that, In step S2, the separation temperature is 30-50℃, and the volume of the concentrated liquid is 1 / 10-1 / 20 of the original extraction liquid volume.

9. The method for oil removal and recovery of waste lithium battery back-extraction solution according to claim 7, characterized in that, In step S3, the cleaning and regeneration process includes backwashing with deionized water for 10-15 minutes, circulating cleaning with dilute acid or alkali solution for 30 minutes, and then rinsing with deionized water until neutral.

10. The method for oil removal and recovery of waste lithium battery back-extraction solution according to claim 7, characterized in that, In step S5, the oil content of the permeate is less than 5 mg / L and the TOC is less than 30 mg / L, so it can be directly used to prepare battery-grade metal salt products.

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