Wastewater treatment system for recycling NMP (N-Methyl Pyrrolidone) solvent in lithium battery

Abstract

The utility model discloses a wastewater treatment system for recycling an NMP (N-Methyl Pyrrolidone) solvent in a lithium battery. The wastewater treatment system comprises a pretreatment device, an IC (Integrated Circuit) reaction device, an SBR (Sequencing Batch Reactor) reaction device and a post-treatment device which are sequentially connected along the conveying direction, the SBR reaction device comprises a plurality of SBR reactors, the water inlet ends of the SBR reactors are connected with the water outlet end of the IC reaction device through first valves, the water outlet ends of the SBR reactors are connected with the post-treatment device through second valves, and the sludge outlet ends of the SBR reactors are connected with the post-treatment device through third valves; the plurality of SBR reactors are arranged at intervals, and an overflow channel is arranged between every two adjacent SBR reactors; the post-treatment device is used for further reducing the COD content and the ammonia nitrogen content in the wastewater. By controlling opening and closing of the first valve, the second valve and the third valve, the SBR reaction device can be switched between an SBR process and an AO process, the load resistance is higher, the concentration of COD in treated wastewater is higher, the stability and compatibility of the system are improved, and the SBR reaction device is more suitable for NMP wastewater under the high-pollution condition.

Description

Technical Field

[0001] The utility model relates to the technical field of wastewater treatment, in particular to a wastewater treatment system for recovering NMP solvent in lithium batteries. Background Art

[0002] NMP (N-methylpyrrolidone) is widely used as an electrolyte additive in lithium battery production. It can improve the conductivity and stability of the battery, and can also reduce the gas generation inside the battery, thereby improving the safety and performance of the battery. In the process of recycling NMP solvents in waste lithium batteries, enterprises often use crushing, pulping, filter pressing and distillation purification processes. In this process, a large amount of production wastewater will be generated, and the wastewater must be treated to meet the discharge standards. The wastewater is mainly composed of nitrogen-containing heterocyclic organic matter, containing high concentrations of COD and total nitrogen. The wastewater can be biodegraded, but it has certain biological toxicity and a slow degradation rate. The total organic carbon content is high, the carbon-nitrogen ratio is very unbalanced, and the denitrification efficiency is extremely low. The existing wastewater treatment system has a poor treatment effect on wastewater, especially some wastewater treatment systems using biochemical systems are not suitable for wastewater with higher concentrations. Utility Model Content

[0003] The utility model aims to solve one of the technical problems in the related art at least to a certain extent. To this end, the utility model proposes a wastewater treatment system for recovering NMP solvent in lithium batteries.

[0004] The utility model embodiment provides a wastewater treatment system for recovering NMP solvent in lithium batteries, wherein the wastewater treatment system for recovering NMP solvent in lithium batteries comprises a pretreatment device, an IC reaction device, an SBR reaction device and a post-treatment device connected in sequence along a conveying direction;

[0005] The pretreatment device is used to remove heavy metal ions and total suspended particles in wastewater;

[0006] The IC reaction device is used to reduce the COD content in wastewater;

[0007] The SBR reaction device comprises a plurality of SBR reactors, the water inlet end of the SBR reactor is connected to the water outlet end of the IC reaction device through a first valve, the water outlet end of the SBR reactor is connected to the post-processing device through a second valve, the mud outlet end of the SBR reactor is connected to the post-processing device through a third valve, the plurality of SBR reactors are arranged at intervals and an overflow channel is provided between two adjacent SBR reactors, and the SBR reactor located at the rear side is connected to the post-processing device through a water outlet pipe;

[0008] The post-treatment device is used to reduce the COD content and ammonia nitrogen content in the wastewater.

[0009] According to the wastewater treatment system for recovering NMP solvent in lithium batteries according to the embodiment of the utility model, at least the following technical effects are achieved: most of the heavy metal ions and total suspended particles in the wastewater are removed after the wastewater passes through the pretreatment device, and then the COD content and denitrification in the wastewater are reduced after passing through the IC reaction device and the SBR reaction device, and finally the COD and content and ammonia nitrogen content in the wastewater are further reduced after passing through the post-treatment device; by controlling the switching of the first valve, the second valve and the third valve, the SBR reaction device can switch between the SBR process and the AO process, with a stronger load resistance, a higher concentration of COD in the treated wastewater, and improved system stability and compatibility, making it more suitable for NMP wastewater under high pollution conditions.

[0010] According to some embodiments of the utility model, the pretreatment device includes an adjusting tank, a value adjusting tank, a coagulation tank, a flocculation tank and a sedimentation tank which are connected in sequence along the conveying direction, the adjusting tank is used to mix the wastewater evenly, the value adjusting tank is used to adjust the pH value of the wastewater to 9-10, the coagulation tank is used to perform a coagulation reaction on the wastewater, the flocculation tank is used to perform a flocculation reaction on the wastewater, the sedimentation tank is used to physically precipitate the wastewater and remove the precipitate, and the water outlet end of the sedimentation tank is connected to the water inlet end of the IC reaction device.

[0011] According to some embodiments of the present utility model, a stirrer is provided in the value adjustment tank, the coagulation tank and the flocculation tank.

[0012] According to some embodiments of the utility model, a disc water distributor, a primary three-phase separator, a secondary three-phase separator and a biogas collector are sequentially arranged inside the IC reaction device from bottom to top, the water inlet end of the disc water distributor is connected to the water outlet end of the pretreatment device, the primary three-phase separator is used to collect biogas, the secondary three-phase separator is used to separate liquid, gas and solid, the biogas collector is used to collect biogas generated in the IC reaction device, and the liquid separated by the secondary three-phase separator enters the SBR reaction device through a pipeline.

[0013] According to some embodiments of the utility model, the first anaerobic zone is between the disc water distributor and the first-level three-phase separator, the second anaerobic zone is between the first-level three-phase separator and the second-level three-phase separator, and a reflux pipe is provided outside the IC reaction device, and the reflux pipe is respectively connected to the first anaerobic zone and the second anaerobic zone, and the reflux pipe is provided with a reflux pump for pumping the liquid in the second anaerobic zone to the first anaerobic zone.

[0014] According to some embodiments of the utility model, the post-treatment device includes an air flotation machine, a sludge thickening tank, a dewatering machine and a NF device, the water outlet end of the SBR reactor is connected to the air flotation machine through a second valve, the mud outlet end of the SBR reactor is connected to the sludge thickening tank through a third valve, the dewatering machine is respectively connected to the sludge thickening tank and the air flotation machine, and the water outlet end of the air flotation machine is connected to the NF device.

[0015] According to some embodiments of the present utility model, the NF device includes a NF water inlet tank, a NF filter and a NF water storage tank, the water inlet end of the NF filter is connected to the NF water inlet tank, the water outlet end of the NF filter is connected to the NF water storage tank, and the water inlet end of the NF water inlet tank is connected to the flotation machine.

[0016] According to some embodiments of the utility model, a sludge scraper is provided on the top of the flotation machine, and the sludge scraper is used to remove sludge in the wastewater.

[0017] According to some embodiments of the utility model, a security filter and a NF filter assembly are provided in the NF filter machine, the water inlet end of the security filter is connected to the NF water inlet tank, and the water outlet end of the security filter is connected to the NF filter assembly.

[0018] According to some embodiments of the utility model, the water outlet end of the IC reaction device is connected to the first branch pipe, and the SBR reactor is connected to the first branch pipe through the first valve respectively; the water inlet end of the post-treatment device is connected to the second branch pipe, and the water outlet end of the SBR reactor is connected to the second branch pipe through the second valve respectively; the mud inlet end of the post-treatment device is connected to the third branch pipe, and the mud outlet end of the SBR reactor is connected to the third branch pipe through the third valve respectively; the first branch pipe is connected to the third branch pipe, and the first branch pipe is provided with a fourth valve for connecting the third branch pipe, and the third branch pipe is provided with a fifth valve on the third branch pipe between the connection point of the first branch pipe and the third branch pipe and the post-treatment device; one end of the water outlet pipe is provided at the upper end of the side wall of the last SBR reactor; a decanter is provided in the SBR reactor, and the decanter is used to decant clarified water from the surface of the wastewater to enter the second branch pipe through the second valve 312.

[0019] Additional aspects and advantages of the present invention will be given in part in the following description, and in part will become apparent from the following description, or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0021] Figure 1 It is a schematic diagram of the structure of a wastewater treatment system for recovering NMP solvent in lithium batteries in some embodiments of the utility model;

[0022] Figure 2 It is a schematic diagram of the structure of the pretreatment device of some embodiments of the utility model;

[0023] Figure 3 It is a schematic diagram of the structure of the IC reaction device of some embodiments of the utility model;

[0024] Figure 4 It is a schematic diagram of the structure of the post-processing device of some embodiments of the utility model;

[0025] Figure 5 It is a schematic diagram of the structure of the NF device of some embodiments of the utility model;

[0026] Figure 6 It is a specific structural schematic diagram of a wastewater treatment system for recovering NMP solvent in lithium batteries according to some embodiments of the utility model.

[0027] Figure Number:

[0028] Pretreatment device 100, regulating tank 110, value adjustment tank 120, coagulation tank 130, flocculation tank 140, sedimentation tank 150, water outlet tank 160, mixer 170;

[0029] IC reaction device 200, disc water distributor 210, primary three-phase separator 220, secondary three-phase separator 230, biogas collector 240, first anaerobic zone 251, second anaerobic zone 252, return pipe 260, return pump 270, first overflow weir 280;

[0030] SBR reaction device 300, SBR reactor 310, first valve 311, second valve 312, third valve 313, overflow channel 320, decanter 330, mud pump 340, outlet pipe 350, fourth valve 351, fifth valve 352, water pump 360, first branch pipe 371, second branch pipe 372, third branch pipe 373;

[0031] Post-processing device 400, air flotation machine 410, mud scraper 411, transition tank 412, reaction tank 413, concentration tank 420, dehydrator 430, NF device 440, NF water inlet tank 441, NF water storage tank 442, NF filter 450, security filter 451, NF filter assembly 452, second overflow weir 460. DETAILED DESCRIPTION

[0032] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0033] In the description of the present invention, it should be understood that descriptions involving orientation, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0034] In the description of the present utility model, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood to exclude the number itself, and "above", "below", "within" etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0035] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0036] The following is a further description of the embodiments of the present invention in conjunction with the accompanying drawings.

[0037] According to some embodiments of the present invention, referring to Figure 1 and Figure 6The wastewater treatment system for recovering NMP solvent in lithium batteries includes a pretreatment device 100, an IC reaction device 200, an SBR reaction device 300 and a post-treatment device 400 connected in sequence along the conveying direction. The pretreatment device 100 is used to remove heavy metal ions and total suspended particles in the wastewater. The IC reaction device 200 is used to reduce the COD content in the wastewater. The SBR reaction device 300 includes a plurality of SBR reactors 310, and an aeration pipe and a decanter 330 are provided in the SBR reactor 310. The water inlet of the SBR reactor 310 is connected to the water outlet of the IC reactor 200 through a first valve 311, the water outlet of the SBR reactor 310 is connected to the post-processing device 400 through a second valve 312, the mud outlet of the SBR reactor 310 is connected to the post-processing device 400 through a third valve 313, a plurality of SBR reactors 310 are arranged at intervals and an overflow channel 320 is provided between two adjacent SBR reactors 310, and the SBR reactor 310 at the rear side is connected to the post-processing device 400 through a water outlet pipe 350. The post-processing device 400 is used to further reduce the COD content and ammonia nitrogen content in the wastewater.

[0038] After the wastewater passes through the pretreatment device 100, most of the heavy metal ions and total suspended particles in the wastewater are removed, and then the COD content and nitrogen removal in the wastewater are reduced through the IC reaction device 200 and the SBR reaction device 300. Finally, the COD and content and ammonia nitrogen content in the wastewater are further reduced through the post-treatment device 400.

[0039] In this embodiment, there are four SBR reactors 310 arranged in sequence along the front-to-back direction. By controlling the switching of the first valve 311, the second valve 312 and the third valve 313 of each SBR reactor 310, the SBR reaction device 300 can switch between the SBR process and the AO process, with stronger load resistance and a higher COD concentration of treated wastewater, thereby improving the stability and compatibility of the system and being more suitable for NMP wastewater under high pollution conditions.

[0040] Reference Figure 1The water outlet of the IC reaction device 200 is connected to the first branch pipe 371, and the SBR reactor 310 is connected to the first branch pipe 371 through the first valve 311. The water inlet of the post-processing device 400 is connected to the second branch pipe 372, and the water outlet of the SBR reactor 310 is connected to the second branch pipe 372 through the second valve 312, and the second branch pipe 372 is provided with a water pump 360. The mud inlet of the post-processing device 400 is connected to the third branch pipe 373, and the mud outlet of the SBR reactor 310 is connected to the third branch pipe 373 through the third valve 313; the first branch pipe 371 is connected to the third branch pipe 373, and the third branch pipe 373 is provided with a mud pump 340. The mud outlet of the SBR reactor 310 is arranged at the bottom of the SBR reactor 310. The first branch pipe 371 is connected to the third branch pipe 373. A fourth valve 351 is provided at one end of the first branch pipe 371 close to the third branch pipe 373. A fifth valve 352 is provided at the third branch pipe 373 between the connection point between the first branch pipe 371 and the third branch pipe 373 and the post-processing device 400. One end of the outlet pipe 350 is provided at the upper end of the side wall of the last SBR reactor 310.

[0041] When the SBR reaction unit 300 is switched to the SBR process, the first valve 311, the second valve 312 and the third valve 313 are all opened, the fourth valve 351 is closed, and the decanter 330 in the SBR reactor 310 starts to work. The decanter 330 can decant the clarified water from the surface of the static wastewater without stirring the sediment, thereby ensuring the effluent quality. Each SBR reactor 310 operates independently, and after six steps of water intake, mixing, aeration, sedimentation, drainage and idleness, the decanter 330 is used to drain the wastewater, and the wastewater enters the post-treatment device 400 through the second branch pipe 372, and the sludge in the SBR reactor 310 is pumped into the post-treatment device 400 through the third branch pipe 373. In the SBR reactor 310, the microporous aeration disk provides the required oxygen within the specified time; when the wastewater has a high load of COD ≥ 3000 mg / L, the inlet BOD is controlled at 0.5-1.5 kgO2 / kgBOD; when the wastewater has a low load of COD < 3000 mg / L, the inlet BOD is controlled at 1.5-2.5 kgO2 / kgBOD.

[0042] When the SBR reaction device 300 is switched to the AO process, the first valves 311 of the last three SBR reactors 310 are closed, and the second valves 312 of the four SBR reactors 310 are closed, and the decanter 330 stops working. The wastewater of the IC reaction device 200 enters the SBR reactor 310 through the first valve 311 of the first SBR reactor 310, and the wastewater in the SBR reactor 310 spreads upward and enters the next SBR reactor 310 through the overflow channel 320, and so on, and the wastewater finally flows out through the outlet pipe 350 of the last SBR reactor 310 and enters the post-treatment device 400. The first SBR reactor 310 starts the agitator as the A pool, and the three subsequent SBR reactors 310 start continuous aeration as the O pool. In the A pool, DO is controlled to be ≤0.2 mg / L. During this process, heterotrophic bacteria hydrolyze suspended pollutants such as starch, fiber, carbohydrates and soluble organic matter in the sewage into organic acids, decompose macromolecular organic matter into small molecular organic matter, and convert insoluble organic matter into soluble organic matter. In the O pool, DO is controlled to be between 3 and 4 mg / L, so that the sludge in the SBR reactor 310 at the rear can be pumped to the SBR reactor 310 at the front, thereby realizing sludge return.

[0043] For example, in this embodiment, the third valves 313 of the first three SBR reactors 310 are closed, the third valve 313 of the last SBR reactor 310 is opened, the fifth valve 352 is closed, the fourth valve 351 is opened, the first valves 311 of the last three SBR reactors 310 are closed, and the first valve 311 of the first SBR reactor 310 is opened, that is, the sludge pump 340 can return the sludge in the last SBR reactor 310 to the first SBR reactor 310, thereby realizing sludge return. By opening or closing different first valves 311 and third valves 313, the starting SBR reactor 310 and the ending SBR reactor 310 of the sludge return can be controlled.

[0044] In this embodiment, the wastewater after passing through the SBR reactor 310 has a COD of ≤500 mg / L, ammonia nitrogen of ≤20 mg / L, and SS of 150-200 mg / L.

[0045] Further, see Figure 2 The pretreatment device 100 includes a regulating tank 110, a value adjusting tank 120, a coagulation tank 130, a flocculation tank 140 and a sedimentation tank 150 which are sequentially connected along the conveying direction. The regulating tank 110 is used to mix the wastewater evenly, the value adjusting tank 120 is used to adjust the pH value of the wastewater to 9-10, the coagulation tank 130 is used to perform coagulation reaction on the wastewater, the flocculation tank 140 is used to perform flocculation reaction on the wastewater, and the sedimentation tank 150 is used to physically precipitate the wastewater and remove the precipitate. The water outlet of the sedimentation tank 150 is connected to the water inlet of the IC reaction device 200.

[0046] Preferably, the pretreatment device 100 further includes a water outlet trough 160 , the water inlet end of the water outlet trough 160 is connected to the sedimentation tank 150 , and the water outlet end of the water outlet trough 160 is connected to the water inlet end of the IC reaction device 200 .

[0047] In this embodiment, the wastewater first enters the regulating tank 110 for uniform mixing and then enters the adjusting tank 120. A 10% calcium hydroxide solution is added to the adjusting tank 120 to adjust the pH of the wastewater to between 9 and 10. The adjusting tank 120 is equipped with a stirrer 170 to fully mix and stir the liquid. The reaction time is 30 minutes. Subsequently, the wastewater overflows into the coagulation tank 130. A 10% PAC solution is added to the coagulation tank 130. The addition amount is 20 mg / L. The reaction time is 30 minutes. The coagulation tank 130 is also equipped with a stirrer 170 to fully mix the material. Then, the wastewater flows from the bottom of the coagulation tank 130 to the flocculation tank 140. A 0.1% PAM anion solution is added to the flocculation tank 140. The addition amount is 10 mg / L. The reaction time is 30 minutes. The flocculation tank 140 is also equipped with a stirrer 170 to fully mix the material. When the mud-water mixture in the flocculation tank 140 overflows to the sedimentation tank 150, precipitation is formed under the action of gravity and the inclined plate of the sedimentation tank 150, and the water overflows from the upper end of the sedimentation tank 150 to the outlet tank 160, and the sludge is discharged at the bottom of the sedimentation tank 150. After the wastewater passes through the pretreatment device 100, the effluent index reaches: heavy metal ≤1mg / L, SS ≤50mg / L.

[0048] Further, see Figure 3The IC reaction device 200 is provided with a disc water distributor 210, a primary three-phase separator 220, a secondary three-phase separator 230 and a biogas collector 240 from bottom to top. The water inlet of the disc water distributor 210 is connected to the water outlet of the pretreatment device 100. The disc water distributor 210 is arranged at the bottom of the IC reaction device 200 so that the wastewater can be evenly distributed in the IC reaction device 200, and the wastewater gradually spreads upward. The primary three-phase separator 220 is used to collect biogas, the secondary three-phase separator 230 is used to separate liquid, gas and solid, the biogas collector 240 is used to collect biogas generated in the IC reaction device 200, and the liquid separated by the secondary three-phase separator 230 enters the SBR reaction device 300 through a pipeline. The first anaerobic zone 251 is between the disc water distributor 210 and the first-stage three-phase separator 220, and the second anaerobic zone 252 is between the first-stage three-phase separator 220 and the second-stage three-phase separator 230. A return pipe 260 is provided outside the IC reaction device 200, and the return pipe 260 is connected to the first anaerobic zone 251 and the second anaerobic zone 252 respectively. A return pump 270 is provided on the return pipe 260 for pumping the liquid in the second anaerobic zone 252 to the first anaerobic zone 251, so that the liquid in the anaerobic zone can be fully mixed and reacted. Since the pretreatment device 100 continuously transports wastewater into the IC reaction device 200, the wastewater in the IC reaction device 200 is generally in a state of spreading upward.

[0049] In the IC reaction device 200, the degradation of organic matter in the wastewater is divided into two stages, the first anaerobic zone 251 is at a high load, and the second anaerobic zone 252 is at a low load. Granular sludge for reacting with wastewater is provided in both the first anaerobic zone 251 and the second anaerobic zone 252. After the wastewater enters the first anaerobic zone 251 from the bottom of the IC reaction device 200, it is evenly mixed with the granular sludge, and most of the organic matter is degraded here and converted into biogas. The upward flow of the mixed liquid and the violent disturbance of the biogas cause the sludge volume to expand into a fluidized state, thereby strengthening the full contact between the incoming water and the granular sludge. The generated biogas is collected by the gas collecting hood of the first-stage three-phase separator 220. In the IC reaction device 200, the organic matter in the wastewater is consumed in large quantities, thereby achieving the effect of removing COD.

[0050] In this embodiment, the water inlet load of the water inlet end of the disc water distributor 210 is controlled at 40kgCOD / (m3·d), the internal temperature of the IC reaction device 200 is maintained at 35-40℃, and the residence time HRT=16~20h. The first anaerobic zone 251 has an upflow rate of 10m / h, which is mainly driven by the liquid flow circulation driven by the airflow generated by the anaerobic reaction. The circulation flow of the return pipe 260 is 240m3 / h, and the upflow rate of the second anaerobic zone 252 is 5m / h. The mixed liquid is first collected by the first-stage three-phase separator, and then separated into water, gas and solid by the second-stage three-phase separator 230. The separated biogas enters the biogas collector 240 at the top of the IC reaction device 200, and the separated wastewater flows out from the overflow weir at the top and enters the SBR reaction device 300. The overflow weir is located between the biogas collector 240 and the second-stage three-phase separator 230. After the wastewater passes through the IC reaction device 200, the COD in the wastewater is ≤8000 mg / L.

[0051] Further, see Figure 4 The post-treatment device 400 includes an air flotation machine 410, a sludge thickening tank 420, a dehydrator 430 and a NF device 440. The water outlet of the SBR reactor 310 is connected to the air flotation machine 410 through a second valve 312, the mud outlet of the SBR reactor 310 is connected to the sludge thickening tank 420 through a third valve 313, the dehydrator 430 is connected to the sludge thickening tank 420 and the air flotation machine 410 respectively, and the water outlet of the air flotation machine 410 is connected to the NF device 440. A sludge scraper 411 is provided on the top of the air flotation machine 410, and the sludge scraper 411 is used to remove sludge in the wastewater.

[0052] In this embodiment, after the outlet of the SBR reactor 310 enters the air flotation machine 410, the SS content in the wastewater is reduced by coagulation reaction in the air flotation machine 410. When the wastewater overflows from the transition tank 412 of the air flotation machine 410 to the reaction tank 413, a 10% PAC solution with a mass fraction of 10 mg / L and a 0.1% PAM solution with a mass fraction of 5 mg / L are added to the air flotation machine 410. In the reaction tank 413, the air pump combines compressed air with the wastewater to form air-dissolved water with fine bubbles, so as to achieve the effect of sludge floating. Then, the sludge is removed by the scraper 411 at the top, and the wastewater flows out to the NF device 440 through the second overflow weir 460. After the wastewater passes through the air flotation machine 410, the COD in the wastewater is ≤400 mg / L, the ammonia nitrogen is ≤20 mg / L, and the SS is ≤50 mg / L.

[0053] Further, see Figure 5NF device 440 includes NF water inlet tank 441, NF filter 450 and NF water storage tank 442. The water inlet end of NF filter 450 is connected to NF water inlet tank 441, the water outlet end of NF filter 450 is connected to NF water storage tank 442, and the water inlet end of NF water inlet tank 441 is connected to air flotation machine 410. NF filter 450 is provided with security filter 451 and NF filter assembly 452. The water inlet end of security filter 451 is connected to NF water inlet tank 441, and the water outlet end of security filter 451 is connected to NF filter assembly 452.

[0054] In this embodiment, the water pump drives the wastewater from the NF water inlet tank 441 into the NF filter 450. The security filter 451 in the NF filter 450 has a built-in filter bag with a filter diameter of 5μm. The wastewater is transported to the NF filter assembly 452 by the high-pressure pump through the security filter 451. The NF water inlet pressure is ≤1MPa, and the pressure difference between the sections is ≤0.2MPa. Under the driving force of the pressure difference, salts and small molecules pass through the nanofiltration membrane, and the membrane pore size is 10-1nm. The NF device 440 adopts a cross-flow filtration method to avoid the blockage phenomenon generated during the dead-end filtration process: the feed liquid flows through the surface of the membrane, and the liquid and small molecules pass through the nanofiltration membrane under the action of pressure, while insoluble substances and macromolecules are retained. The filtered wastewater then enters the NF water storage tank 442 from the NF filter 450. The COD in the wastewater is ≤100mg / L, ammonia nitrogen is ≤10mg / L, SS is ≤10mg / L, salt is ≤200mg / L, pH is 7-9, and the effluent meets the third level of the "Comprehensive Sewage Discharge Standard GB8978-1996" and can be directly reused or discharged.

[0055] In the description of this specification, the description with reference to the term "some embodiments" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0056] Although the embodiments of the present invention have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A wastewater treatment system for recovering NMP solvent from lithium batteries, characterized in that: It comprises a pre-treatment device (100), an IC reaction device (200), an SBR reaction device (300) and a post-treatment device (400) which are sequentially connected along a conveying direction; The pretreatment device (100) is used to remove heavy metal ions and total suspended particles in wastewater; The IC reaction device (200) is used to reduce the COD content in the wastewater; The SBR reaction device (300) comprises a plurality of SBR reactors (310), wherein the water inlet end of the SBR reactor (310) is connected to the water outlet end of the IC reaction device (200) via a first valve (311), the water outlet end of the SBR reactor (310) is connected to the post-processing device (400) via a second valve (312), and the mud outlet end of the SBR reactor (310) is connected to the post-processing device (400) via a third valve (313); the plurality of SBR reactors (310) are arranged in sequence and an overflow channel (320) is provided between two adjacent SBR reactors (310), and the last SBR reactor (310) is connected to the post-processing device (400) via a water outlet pipe (350); The post-treatment device (400) is used to reduce the COD content and ammonia nitrogen content in the wastewater.

2. The wastewater treatment system for recovering NMP solvent in lithium batteries according to claim 1, characterized in that: The pretreatment device (100) comprises a regulating tank (110), a value adjustment tank (120), a coagulation tank (130), a flocculation tank (140) and a sedimentation tank (150) which are sequentially connected along the conveying direction, wherein the regulating tank (110) is used to mix the wastewater evenly, the value adjustment tank (120) is used to adjust the pH value of the wastewater to 9-10, the coagulation tank (130) is used to perform a coagulation reaction on the wastewater, the flocculation tank (140) is used to perform a flocculation reaction on the wastewater, and the sedimentation tank (150) is used to perform physical precipitation on the wastewater and remove sediments, and the water outlet of the sedimentation tank (150) is connected to the water inlet of the IC reaction device (200).

3. The wastewater treatment system for recovering NMP solvent in lithium batteries according to claim 2, characterized in that: A stirrer (170) is provided in the value adjustment tank (120), the coagulation tank (130) and the flocculation tank (140).

4. The wastewater treatment system for recovering NMP solvent in lithium batteries according to claim 1, characterized in that: The IC reaction device (200) is provided with a disc water distributor (210), a primary three-phase separator (220), a secondary three-phase separator (230) and a biogas collector (240) in order from bottom to top. The water inlet end of the disc water distributor (210) is connected to the water outlet end of the pretreatment device (100). The primary three-phase separator (220) is used to collect biogas. The secondary three-phase separator (230) is used to separate liquid, gas and solid. The biogas collector (240) is used to collect biogas generated in the IC reaction device (200). The liquid separated by the secondary three-phase separator (230) enters the SBR reaction device (300) through a pipeline.

5. The wastewater treatment system for recovering NMP solvent in lithium batteries according to claim 4, characterized in that: A first anaerobic zone (251) is located between the disc water distributor (210) and the first-stage three-phase separator (220), and a second anaerobic zone (252) is located between the first-stage three-phase separator (220) and the second-stage three-phase separator (230). A return pipe (260) is provided outside the IC reaction device (200), and the return pipe (260) is connected to the first anaerobic zone (251) and the second anaerobic zone (252) respectively. A return pump (270) is provided on the return pipe (260) for pumping liquid in the second anaerobic zone (252) to the first anaerobic zone (251).

6. The wastewater treatment system for recovering NMP solvent in lithium batteries according to claim 1, characterized in that: The post-treatment device (400) comprises an air flotation machine (410), a sludge thickening tank (420), a dewatering machine (430) and a NF device (440); the water outlet of the SBR reactor (310) is connected to the air flotation machine (410) via a second valve (312); the mud outlet of the SBR reactor (310) is connected to the sludge thickening tank (420) via a third valve (313); the dewatering machine (430) is connected to the sludge thickening tank (420) and the air flotation machine (410) respectively; and the water outlet of the air flotation machine (410) is connected to the NF device (440).

7. The wastewater treatment system for recovering NMP solvent in lithium batteries according to claim 6, characterized in that: The NF device (440) comprises a NF water inlet tank (441), a NF filter (450) and a NF water storage tank (442); the water inlet end of the NF filter (450) is connected to the NF water inlet tank (441), the water outlet end of the NF filter (450) is connected to the NF water storage tank (442), and the water inlet end of the NF water inlet tank (441) is connected to the flotation machine (410).

8. The wastewater treatment system for recovering NMP solvent in lithium batteries according to claim 6, characterized in that: A sludge scraper (411) is provided on the top of the air flotation machine (410), and the sludge scraper (411) is used to remove sludge in the wastewater.

9. The wastewater treatment system for recovering NMP solvent in lithium batteries according to claim 7, characterized in that: The NF filter (450) is provided with a security filter (451) and a NF filter assembly (452). The water inlet end of the security filter (451) is connected to the NF water inlet tank (441), and the water outlet end of the security filter (451) is connected to the NF filter assembly (452).

10. The wastewater treatment system for recovering NMP solvent in lithium batteries according to claim 1, characterized in that: The water outlet of the IC reaction device (200) is connected to the first branch pipe (371), and the SBR reactor (310) is connected to the first branch pipe (371) through the first valve (311); the water inlet of the post-treatment device (400) is connected to the second branch pipe (372), and the water outlet of the SBR reactor (310) is connected to the second branch pipe (372) through the second valve (312); the mud inlet of the post-treatment device (400) is connected to the third branch pipe (373), and the mud outlet of the SBR reactor (310) is connected to the third branch pipe (373) through the third valve (313); the first branch pipe (371 ) is connected to the third branch pipe (373), the first branch pipe (371) is provided with a fourth valve (351) for connecting to the third branch pipe (373), and a fifth valve (352) is provided on the third branch pipe (373) between the connection point between the first branch pipe (371) and the third branch pipe (373) and the post-treatment device (400); one end of the outlet pipe (350) is arranged at the upper end of the side wall of the last SBR reactor (310); a decanter (330) is provided in the SBR reactor (310), and the decanter (330) is used to decant clarified water from the surface of the wastewater so as to enter the second branch pipe (372) through the second valve (312).

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