A wastewater treatment system for ternary lithium-ion batteries based on gaseous membrane technology

Abstract

This invention discloses a ternary lithium-ion battery wastewater treatment system based on gaseous membrane technology. It includes a mother liquor treatment system and a washing liquid treatment system. The mother liquor treatment system comprises a mother liquor conditioning tank, a complex-breaking reaction tank, a sedimentation tank, a multi-stage gaseous membrane module, an evaporator, and a centrifugal separator, connected in sequence. The complex-breaking reaction tank is also connected to an alkaline solution tank, and the multi-stage gaseous membrane module is also connected to an acid solution tank. The liquid in the centrifugal separator is connected to either the mother liquor conditioning tank or the evaporator. The washing liquid treatment system includes a pretreatment unit and a reverse osmosis concentration unit connected in sequence. The concentrated liquid obtained from the reverse osmosis concentration unit is connected to the mother liquor conditioning tank. This invention combines gaseous membrane denitrification with intelligent control. By constructing a parameter optimization mechanism based on real-time water quality data, it achieves rapid response and dynamic adjustment of key operating parameters, thereby effectively improving the system's denitrification efficiency and operational stability.

Description

Technical Field

[0001] This utility model relates to a system for treating wastewater containing ammonia nitrogen and heavy metal ions generated during the production of lithium battery ternary cathode material precursors. It adopts a gaseous membrane method to achieve efficient removal and resource recovery of ammonia nitrogen, and belongs to the field of wastewater treatment technology. Background Technology

[0002] The development of the new energy industry has driven the continuous increase in the production of lithium batteries, especially ternary lithium batteries. As the core cathode material of lithium-ion batteries, the production and cleaning of ternary materials will generate a large amount of complex industrial wastewater. This type of wastewater is characterized by high ammonia nitrogen concentration (usually 1000-5000 mg / L), high salt content, complex wastewater composition, and large fluctuations in water quality.

[0003] Currently, the existing treatment technologies have the following problems: (1) The treatment mode is extensive, and the mother liquor and washing liquid are often mixed for treatment, resulting in "over-treatment" of the washing liquid and waste of reagents. The mother liquor is diluted, which leads to a decrease in denitrification efficiency of more than 30%. (2) The existing treatment systems mostly operate with fixed parameters, which makes it difficult to cope with the large fluctuations in the composition of ternary wastewater, resulting in the effluent water quality easily exceeding the standard, and serious waste of energy and reagents. (3) The system has poor coordination. The pretreatment, denitrification, evaporation and other units operate independently and lack parameter linkage, resulting in delayed membrane fouling warnings, easy agglomeration of evaporation crystals, and high system operation and maintenance costs. (4) As one of the core problems, ammonia nitrogen treatment mostly uses stripping (stripping) method, which is significantly affected by temperature. The treatment efficiency drops by more than 30% in winter and generates ammonia-containing waste gas, causing secondary pollution. Summary of the Invention

[0004] The technical problem to be solved by this utility model is that existing wastewater treatment systems suffer from low ammonia nitrogen removal efficiency, poor system stability, and insufficient resource recovery. This utility model provides a ternary wastewater treatment system that is highly efficient and energy-saving, has strong anti-pollution capabilities, and can achieve intelligent operation.

[0005] To address the aforementioned problems, this invention provides a ternary lithium-ion battery wastewater treatment system based on a gaseous membrane method. The system includes a mother liquor treatment system and a washing liquid treatment system. The mother liquor treatment system comprises a mother liquor conditioning tank, a complex-breaking reaction tank, a sedimentation tank, a multi-stage gaseous membrane module, an evaporator, and a centrifugal separator, connected in sequence. The complex-breaking reaction tank is also connected to an alkaline solution tank, and the multi-stage gaseous membrane module is also connected to an acid solution tank. The liquid in the centrifugal separator is connected to the mother liquor conditioning tank or the evaporator via a pipeline. The washing liquid treatment system includes a pretreatment unit and a reverse osmosis concentration unit connected in sequence. The reverse osmosis concentration unit contains a reverse osmosis membrane, and the concentrated liquid obtained from the reverse osmosis concentration unit is connected to the mother liquor conditioning tank. The reverse osmosis concentration unit intelligently adjusts the high-pressure pump frequency and recovery rate based on the influent salinity and pressure, reducing energy consumption while ensuring the quality of the produced water. Furthermore, it predicts membrane fouling based on the trend of transmembrane pressure difference changes and optimizes the chemical cleaning cycle.

[0006] Preferably, the multi-stage gaseous membrane module is a tubular gaseous membrane denitrification device comprising at least two membrane modules; the tubular gaseous membrane denitrification device is equipped with an operation optimization and early warning system, which includes an ammonia nitrogen concentration sensor, a pH sensor, a temperature sensor, and a flow sensor installed at the feed inlet; a differential pressure sensor installed at the inlet and outlet of the membrane module; and a pH sensor, a density sensor, and a liquid level sensor installed in the acid circulation system. This operation optimization and early warning system is configured to adjust process parameters in real time based on the aforementioned sensor data, and automatically switch storage tanks and replenish fresh acid when the absorbent density reaches a set value.

[0007] Preferably, the acid pool is an acid absorption tank.

[0008] Preferably, the complex-breaking reaction tank and sedimentation tank are equipped with an intelligent dosing and sludge discharge control system.

[0009] More preferably, the complexation breaking reaction tank is equipped with an ORP sensor and an online heavy metal ion concentration monitor.

[0010] More preferably, the sedimentation tank is equipped with a turbidity sensor. The intelligent dosing and sludge removal control system adjusts the alkali dosage in real time based on the sensor feedback data, and intelligently controls the sludge removal cycle and duration of the sedimentation tank.

[0011] Preferably, the evaporation device is any one of a mechanical vapor recompression evaporator, a multi-effect evaporator, or a thermal vapor recompression evaporator.

[0012] Preferably, the pretreatment unit includes a washing liquid conditioning tank and a security filter in sequence.

[0013] More preferably, the condensate obtained from the evaporation device is connected to the washing liquid conditioning tank.

[0014] More preferably, an ultrafiltration membrane is provided between the security filter and the reverse osmosis membrane.

[0015] This utility model also provides a ternary wastewater treatment method, using the above-mentioned wastewater treatment system, the specific steps of which include: S1: The ternary washing solution enters the pretreatment unit, and after adjustment, filtration, ultrafiltration and reverse osmosis treatment, the clear liquid is reused and the concentrated liquid enters the mother liquor conditioning tank. S2: After the ternary mother liquor is balanced in the mother liquor conditioning tank, it is pumped into the complex-breaking reaction tank, and alkaline solution is added to carry out the complex-breaking reaction. Then it enters the sedimentation tank for solid-liquid separation. The generated heavy metal sludge is transported off-site for disposal, and the supernatant enters the multi-stage gaseous membrane module. S3: The supernatant is pumped into the tube side of the multi-stage gaseous membrane module, while the acid absorbent is pumped from the acid tank into its shell side and circulated. Free ammonia in the wastewater permeates through the membrane pores and is absorbed by the acid absorbent to form ammonium salts. When the concentration of ammonium salts in the acid absorbent in the acid tank reaches saturation, it is discharged for resource recovery and fresh acid absorbent is added. S4: Wastewater after denitrification by gas membrane enters the evaporation unit for concentration and evaporation, and the resulting condensate is reused in the mother liquor conditioning tank; S5: The crystal slurry produced after evaporation and concentration enters the centrifugal separation device for solid-liquid separation to obtain high-purity ammonium salt crystals and mother liquor. The mother liquor is returned to the mother liquor conditioning tank or the evaporation device for further processing.

[0016] Preferably, the alkaline solution in S2 is at least one of sodium hydroxide, calcium hydroxide, and quicklime.

[0017] Preferably, the acid absorption solution in S3 is at least one of sulfuric acid, nitric acid, and hydrochloric acid, and its mass concentration is 5-10%.

[0018] This invention combines gaseous membrane denitrification with intelligent control. By constructing a parameter optimization mechanism based on real-time water quality data, it achieves rapid response and dynamic adjustment of key operating parameters, thereby effectively improving the system's denitrification efficiency and operational stability.

[0019] Compared with the prior art, the beneficial effects of this utility model are as follows: 1. High and stable ammonia nitrogen removal efficiency: The gaseous membrane method is used for nitrogen removal, combined with an intelligent control system to adjust the operating parameters in real time. It is not affected by fluctuations in wastewater temperature and ammonia nitrogen concentration. The ammonia nitrogen removal rate is stable, and high-purity ammonium sulfate is produced as a by-product, realizing resource recovery.

[0020] 2. Intelligent operation and maintenance: Through intelligent monitoring and calculation, the system can predict membrane fouling, adaptively adjust process parameters, and intelligently diagnose and warn of equipment status, thereby reducing system operating costs and minimizing human intervention.

[0021] 3. Reduced operating costs: Intelligent control reduces chemical waste, and the online gas membrane cleaning program reduces the frequency of membrane module replacement, extends membrane life, and reduces overall operating costs.

[0022] 4. Improved resource recovery efficiency: Ensure the stability of the ammonia recovery process and improve the purity and recovery rate of by-products such as ammonium sulfate. Attached Figure Description

[0023] Figure 1 A schematic diagram of the ternary lithium-ion battery wastewater treatment system based on the gaseous membrane method provided by this utility model. Detailed Implementation

[0024] To make this utility model more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0025] Example 1 like Figure 1 As shown, this utility model provides a ternary lithium-ion battery wastewater treatment system based on gaseous membrane technology. It includes a mother liquor treatment system and a washing liquid treatment system. The mother liquor treatment system comprises a mother liquor conditioning tank 1, a complex-breaking reaction tank 2, a sedimentation tank 3, a multi-stage gaseous membrane module 4, an evaporator 5, and a centrifugal separator 6, connected in sequence. The complex-breaking reaction tank 2 is also connected to an alkaline solution tank 7, and the multi-stage gaseous membrane module 4 is also connected to an acid absorption tank 8. The liquid in the centrifugal separator 6 is connected to the mother liquor conditioning tank 1 or the evaporator 5 via a pipeline. The washing liquid treatment system comprises a washing liquid conditioning tank 9, a security filter 10 (the washing liquid conditioning tank 9 and the security filter 10 constitute a pretreatment unit), an ultrafiltration membrane 11, and a reverse osmosis concentration unit, connected in sequence. The reverse osmosis concentration unit contains a reverse osmosis membrane 12, and the concentrated liquid obtained from the reverse osmosis concentration unit is connected to the mother liquor conditioning tank 1. The condensate obtained from the evaporator 5 is connected to the washing liquid conditioning tank 9.

[0026] The multi-stage gaseous membrane module 4 is a tubular gaseous membrane denitrification device comprising at least two membrane modules. The tubular gaseous membrane denitrification device is equipped with an operation optimization and early warning system, which includes an ammonia nitrogen concentration sensor, a pH sensor, a temperature sensor, and a flow sensor located at the feed inlet; differential pressure sensors located at the membrane module inlet and outlet; and a pH sensor, a density sensor, and a level sensor located in the acid circulation system. This operation optimization and early warning system is configured to adjust process parameters in real time based on the aforementioned sensor data, and automatically switch storage tanks and replenish fresh acid when the absorbent density reaches a set value, such as 20%.

[0027] The complex-breaking reaction tank 2 and sedimentation tank 3 are equipped with an intelligent dosing and sludge removal control system. The complex-breaking reaction tank 2 is equipped with an ORP sensor and an online heavy metal ion concentration monitor. The sedimentation tank 3 is equipped with a turbidity sensor. The intelligent dosing and sludge removal control system adjusts the alkali dosage in real time based on sensor feedback data and intelligently controls the sludge removal cycle and duration of the sedimentation tank.

[0028] The evaporation device 5 is any one of a mechanical vapor recompression evaporator, a multi-effect evaporator, or a thermal vapor recompression evaporator.

[0029] A ternary wastewater treatment process based on tubular gaseous membrane denitrification comprises the following steps: S1: The ternary washing water enters the washing liquid treatment system. After adjustment, filtration, ultrafiltration and reverse osmosis treatment, the clear liquid is reused and the concentrated liquid enters the mother liquor conditioning tank. S2: After the ternary mother liquor is balanced in the mother liquor conditioning tank, it is pumped into the complex breaking reaction tank, and alkaline solution is added to carry out the complex breaking reaction. Then it enters the sedimentation tank for solid-liquid separation. The generated heavy metal sludge is transported off-site for disposal, and the supernatant enters the tubular gas membrane denitrification device. S3: Pump the supernatant into the tube side of the tubular gas membrane module, and at the same time pump the acid absorbent in the acid absorption tank 8 into its shell side for circulation; free ammonia in the wastewater permeates through the membrane pores and is absorbed by the acid absorbent to form ammonium salt; when the concentration of ammonium salt in the acid absorbent reaches saturation, it is discharged for resource recovery and fresh acid absorbent is added. S4: The wastewater after denitrification by gas membrane enters the evaporation device for concentration and evaporation, and the resulting condensate is reused in the washing liquid conditioning tank 9; S5: The crystal slurry produced after evaporation and concentration enters the centrifugal separation device 6 for solid-liquid separation to obtain high-purity ammonium salt crystals and mother liquor. The mother liquor is returned to the mother liquor conditioning tank 1 or the evaporation device 5 for further processing.

[0030] The above process is used to implement graded resource recovery treatment of ternary wastewater. The ternary washing liquid (ammonia nitrogen 600 mg / L, SS 300 mg / L) is homogenized and equalized in a washing liquid equalization tank, then sequentially passes through a security filter and an ultrafiltration membrane to obtain pretreated permeate with an SDI < 5. This permeate enters a two-stage reverse osmosis system: RO1 permeate (conductivity < 0.8 μS / cm) is directly reused in the production process; RO2 concentrate (ammonia nitrogen 4000 mg / L) is sent to a mother liquor equalization tank. The system predicts membrane fouling by monitoring pressure differential changes and dynamically adjusts the high-pressure pump frequency and recovery rate (70%-75%) to optimize the cleaning cycle.

[0031] The mother liquor is mixed with RO2 concentrate (ammonia nitrogen 8000 mg / L) and then enters the complex-breaking reaction tank. The pH is controlled at 12.5-13.0 by intelligent addition of NaOH, effectively breaking down heavy metal complexes. The supernatant after coagulation and sedimentation (heavy metals ≤0.1 mg / L) enters the tubular gas membrane denitrification unit. Under optimized parameters (pH 11, feed flow rate 1.3 m / s; absorbent is 10% dilute sulfuric acid, absorbent flow rate 0.7 m / s), efficient denitrification (effluent ammonia nitrogen ≤10 mg / L) is achieved, while simultaneously recovering a 20% concentration of ammonium sulfate solution.

[0032] After denitrification, the mother liquor is concentrated by MVR evaporation (75-85℃, -0.08MPa), and the condensate (conductivity <15μS / cm) is recycled to the washing liquid conditioning tank. The concentrated crystal slurry is centrifuged to obtain sodium sulfate product with a purity ≥98.5%, and the centrifuged mother liquor is returned to the system for recycling. The entire process is controlled by an intelligent control system to achieve membrane fouling early warning, adaptive parameter adjustment, and precise reagent dosing, ensuring stable and efficient system operation.

Claims

1. A gaseous membrane-based three-element lithium-ion battery wastewater treatment system, characterized by, The system includes a mother liquor treatment system and a washing liquid treatment system. The mother liquor treatment system includes a mother liquor conditioning tank (1), a complex-breaking reaction tank (2), a sedimentation tank (3), a multi-stage gaseous membrane module (4), an evaporation device (5), and a centrifugal separation device (6) connected in sequence. The complex-breaking reaction tank (2) is also connected to an alkaline solution tank (7), and the multi-stage gaseous membrane module (4) is also connected to an acid solution tank. The liquid in the centrifugal separation device (6) is connected to the mother liquor conditioning tank (1) or the evaporation device (5) through a pipeline. The washing liquid treatment system includes a pretreatment unit and a reverse osmosis concentration unit connected in sequence. The reverse osmosis concentration unit is equipped with a reverse osmosis membrane (12). The concentrated liquid obtained by the reverse osmosis concentration unit is connected to the mother liquor conditioning tank (1).

2. The gaseous membrane based three-way lithium-ion battery wastewater treatment system of claim 1, wherein, The multi-stage gaseous membrane module (4) is a tubular gaseous membrane denitrification device including at least two membrane modules; the tubular gaseous membrane denitrification device is equipped with an operation optimization and early warning system, which includes an ammonia nitrogen concentration sensor, a pH sensor, a temperature sensor and a flow sensor installed at the feed inlet, a differential pressure sensor installed at the inlet and outlet of the membrane module, and a pH sensor, a density sensor and a liquid level sensor installed in the acid circulation system.

3. The gaseous membrane based three-way lithium-ion battery wastewater treatment system of claim 1, wherein, The acid pool is an acid absorption tank (8).

4. The gaseous membrane based three-way lithium-ion battery wastewater treatment system of claim 1, wherein, The complex-breaking reaction tank (2) and sedimentation tank (3) are equipped with an intelligent dosing and sludge discharge control system.

5. The ternary lithium-ion battery wastewater treatment system based on gaseous membrane method as described in claim 4, characterized in that, The complex-breaking reaction tank (2) is equipped with an ORP sensor and an online monitoring instrument for heavy metal ion concentration.

6. The ternary lithium-ion battery wastewater treatment system based on gaseous membrane method as described in claim 4, characterized in that, The sedimentation tank (3) is equipped with a turbidity sensor.

7. The ternary lithium-ion battery wastewater treatment system based on gaseous membrane method as described in claim 1, characterized in that, The evaporation device (5) is any one of a mechanical vapor recompression evaporator, a multi-effect evaporator, or a thermal vapor recompression evaporator.

8. The ternary lithium-ion battery wastewater treatment system based on gaseous membrane method as described in claim 1, characterized in that, The pretreatment unit includes, in sequence, a washing liquid conditioning tank (9) and a security filter (10).

9. The ternary lithium-ion battery wastewater treatment system based on gaseous membrane method as described in claim 8, characterized in that, The condensate obtained from the evaporation device (5) is connected to the washing liquid conditioning tank (9).

10. The ternary lithium-ion battery wastewater treatment system based on gaseous membrane method as described in claim 8, characterized in that, An ultrafiltration membrane (11) is provided between the security filter (10) and the reverse osmosis membrane (12).

Images