Five-cavity-bipolar membrane electrodialysis device and method for purifying degraded amine liquid

Abstract

The invention discloses a five-cavity-bipolar membrane electrodialysis device and a five-cavity-bipolar membrane electrodialysis method for purifying degraded amine liquid. The electrodialysis device comprises an integrated membrane stack adopting a flat plate type membrane stack structure, the arrangement mode of the membrane stack is as follows: an anode plate, an anode chamber, an anti-pollution ultrafiltration membrane, a pretreatment cavity, an anion exchange membrane, an amine liquid regeneration cavity, a bipolar membrane, a high-value conversion cavity, a cation exchange membrane, a raw material salt cavity, an acid-resistant anion membrane, a cathode chamber and a cathode plate are connected in sequence; clamping plates are respectively attached to the outer sides of the anode plate and the cathode plate, and the whole membrane stack is sealed and pressed through the two clamping plates to form a five-function cavity structure; wherein the nightside of the bipolar membrane faces the amine liquid regeneration cavity, the sunny side of the bipolar membrane faces the high-value conversion cavity, and the bipolar membrane is a sulfonated covalent organic framework composite bipolar membrane. The device does not need additional acid and alkali, the amine liquid regeneration rate is larger than or equal to 90%, the heat-stable salt removal rate is larger than or equal to 90%, the high-value salt purity is larger than or equal to 90%, and the device is suitable for treatment of deteriorated amine liquid in the fields of natural gas desulfurization, carbon capture and the like.

Description

Technical Field

[0001] This invention belongs to the field of amine liquid treatment technology, specifically relating to a five-chamber bipolar membrane electrodialysis device and method for purifying degraded amine liquid, which is particularly suitable for treating degraded amine liquid generated during natural gas desulfurization and carbon capture processes. Background Technology

[0002] Organic amine absorption is a mainstream technology for industrial flue gas desulfurization and carbon capture. However, during recycling, amine solutions are easily oxidized and degraded to produce heat-stable salts (sulfates, chloride ions, acetates, etc.), leading to decreased absorption efficiency, increased equipment corrosion, and higher energy consumption. Therefore, amine purification technology is crucial for organic amine absorption.

[0003] Existing amine purification technologies mainly include ion exchange and electrodialysis: ion exchange requires frequent resin regeneration, generating a large amount of alkaline residue and wastewater, resulting in high environmental costs; while electrodialysis does not require resin regeneration, it has significant technical bottlenecks.

[0004] Existing bipolar membrane electrodialysis devices mostly employ a three- or four-chamber structure (such as the three-chamber electrodialysis unit disclosed in CN205151858U), lacking a pretreatment unit. Suspended solids and organic matter in the deteriorated amine solution easily cause membrane fouling, leading to a reduction in membrane lifespan of more than 30%. Secondly, heat-stable salts are often converted into low-value mixed acids (such as a mixture of sulfuric acid and hydrochloric acid), resulting in low resource utilization. Furthermore, the bipolar membrane is directly exposed to the anodic oxidation environment, making it susceptible to corrosion by oxygen generated at the anode, leading to a decrease in water dissociation efficiency. For example, the bipolar membrane amine solution regeneration device disclosed in CN113457451A, although achieving self-sufficiency in alkali solution, requires further treatment of the byproduct mixed acid and does not solve the membrane fouling problem, with an amine solution regeneration rate of only 85%–90%. Patent CN202311293894.3 discloses a system and method for removing amine-stabilized salts from a liquid. The system includes a raw material tank, a fine filtration assembly, an electrodialysis membrane stack, and a circulation flushing assembly. However, its circulation flushing can only handle conventional particulate matter clogging, and its flushing effect on chemical scaling is limited. This still leads to a limited service life of the membrane, requiring regular replacement of the membrane assembly and increasing costs.

[0005] Therefore, developing a novel electrodialysis device that combines pretreatment function, high-value conversion capability, and anti-pollution properties is of great significance for improving the economic efficiency and stability of amine solution purification. Summary of the Invention

[0006] The purpose of this invention is to provide a five-chamber bipolar membrane electrodialysis device and method for purifying degraded amine solutions, which solves the technical defects of existing devices such as serious membrane fouling, low value of by-products, and easy oxidation of bipolar membranes, and realizes deep purification of degraded amine solutions, efficient regeneration of amine solutions, and high-value utilization of heat-stable salts.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows.

[0008] The present invention provides a five-chamber bipolar membrane electrodialysis device for purifying deteriorated amine solutions, comprising: an integrated membrane stack, a circulating supply system, and an intelligent monitoring system; The integrated membrane stack adopts a planar membrane stack structure, and the membrane stack is arranged in the following order: anode plate - anode chamber - antifouling ultrafiltration membrane - pretreatment chamber - anion exchange membrane - amine regeneration chamber - bipolar membrane - high-value conversion chamber - cation exchange membrane - raw material salt chamber - acid-resistant anion membrane - cathode chamber - cathode plate. Clamping plates are respectively attached to the outside of the anode plate and the cathode plate, and the entire membrane stack is sealed and compressed by the two clamping plates to form a five-functional chamber structure. Among them, the negative side of the bipolar membrane faces the amine regeneration chamber, and the positive side faces the high-value conversion chamber. The bipolar membrane is a sulfonated covalent organic framework composite bipolar membrane. The circulating supply system includes a degraded amine liquid storage tank, a pretreatment liquid storage tank, an amine liquid regeneration storage tank, a high-value salt storage tank, a raw material salt storage tank, an electrode liquid storage tank, and corresponding transfer pumps for each. The outlet of the degraded amine liquid storage tank is connected to the inlet of the amine liquid regeneration chamber, and the inlet of the amine liquid regeneration storage tank is connected to the outlet of the amine liquid regeneration chamber, forming a circulation path. The pretreatment liquid storage tank is connected to the pretreatment chamber, forming a circulation path. The high-value salt storage tank is connected to the high-value conversion chamber, forming a circulation path. The raw material salt storage tank is connected to the raw material salt chamber, forming a circulation path. The outlet of the electrode liquid storage tank is divided into two branches, which are respectively connected to the inlet of the anode chamber and the inlet of the cathode chamber. The two branches of the anode chamber outlet and the cathode chamber outlet merge and connect to the inlet of the electrode liquid storage tank, forming a circulation path. The intelligent monitoring system ( Figure 1 The device (integrated with a DC regulated power supply) includes a PLC controller and pH sensors, conductivity sensors, and flow sensors respectively located on the inlet and outlet pipelines of each cavity. The PLC controller is electrically connected to the DC regulated power supply, the PLC control valves of each liquid storage tank, the delivery pump, and the pulse generator.

[0009] Furthermore, the five-chamber bipolar membrane electrodialysis device for purifying degraded amine solution of the present invention also includes an online cleaning module. The online cleaning module contains a cleaning solution storage tank and a pulse generator; the cleaning solution storage tank is connected to the degraded amine solution storage tank, the pretreatment solution storage tank, the high-value salt storage tank, the raw material salt storage tank, and the electrode solution storage tank via three-way valves.

[0010] In addition, to improve the cleaning efficiency of the membrane stack and remove scale buildup, an ultrasonic transducer is embedded inside the membrane stack; preferably, an ultrasonic transducer is embedded inside the anode plate and an ultrasonic transducer is installed inside the cathode plate.

[0011] Preferably, the antifouling ultrafiltration membrane is a PVDF-modified charged ultrafiltration membrane with a pore size of 50–200 nm and a surface grafted with β-cyclodextrin groups; the anion exchange membrane is a quaternized polyethersulfone homogeneous membrane with an ion exchange capacity ≥1.8 mmol / g; the acid-barrier anion membrane is a fluorocarbon resin-based modified anion membrane with an acid permeability coefficient ≤0.02 m / h; and the cation exchange membrane is a sulfonated polyethersulfone (SPES) homogeneous cation exchange membrane with an ion exchange capacity ≥1.5 mmol / g.

[0012] Preferably, the pretreatment chamber is provided with a honeycomb flow channel mesh with a flow channel width of 2-3 mm, and the surface of the mesh is loaded with a nano-TiO2 photocatalytic coating; the flow channel mesh of the amine regeneration chamber, the high-value conversion chamber and the raw material salt chamber is a rhombic mesh structure with a porosity ≥85%.

[0013] Preferably, the intermediate catalyst layer of the bipolar membrane is Zn-Ni bimetallic ZIF-derived porous carbon with a loading of 0.8–1.2 mg / cm³. 2 The cation exchange membrane is a sulfonated polyether ether ketone composite membrane with a sulfonation degree of 60% to 80%.

[0014] Preferably, the cleaning solution of the online cleaning module is a mixture of 0.1-0.3 mol / L citric acid and 0.05-0.1 mol / L EDTA, and the pulse generator operates at a frequency of 0.5-2 Hz with a duty cycle of 30%-60%.

[0015] The present invention also provides a method for purifying deteriorated amine solution, using the aforementioned five-chamber bipolar membrane electrodialysis device, comprising the following steps: S1. Pretreatment: The degraded amine solution is transported to the pretreatment chamber through the degraded amine solution storage tank. The suspended solids and large molecular organic matter are intercepted by the anti-fouling ultrafiltration membrane, and the permeate enters the amine solution regeneration chamber. S2. Amine Regeneration: Start the DC regulated power supply. Thermally stable salt anions in the amine regeneration chamber migrate through the anion exchange membrane into the high-value conversion chamber. OH groups generated by the dissociation of the bipolar membrane anion exchanger... - The free amine enters the amine regeneration chamber and reacts with the amine salt to regenerate the amine. The regenerated amine is then recovered from the amine regeneration storage tank. S3. High-value conversion: The high-value cation salt solution in the raw salt storage tank is sent into the raw salt chamber. The cations migrate into the high-value conversion chamber through the cation exchange membrane and combine with the thermally stable salt anions to generate high-value inorganic salts, which are collected by the high-value salt storage tank.

[0016] The purification method described in this invention also includes the system maintenance process of the five-chamber bipolar membrane electrodialysis device: when the membrane stack resistance increases by more than 15%, the online cleaning module is started, and the pulse cleaning solution is circulated and rinsed for 40 to 60 minutes; at the same time, the ultrasonic transducer can also be turned on to assist in descaling.

[0017] Compared with the prior art, the beneficial effects of the present invention are: The five-chamber bipolar membrane electrodialysis device of this invention for purifying degraded amine solution has strong membrane fouling control capabilities. The pretreatment chamber can remove more than 98% of suspended solids and macromolecular organic matter. With the online cleaning system, the membrane stack resistance increase is ≤10% / 100h, far lower than the 30% / 100h of traditional devices. The by-products are of high value, converting heat-stable salts into high-value inorganic salts such as lithium sulfate and potassium chloride, rather than low-value mixed acids, generating an additional economic benefit of 80-120 yuan per ton of degraded amine solution. The amine solution regeneration efficiency is high, with bipolar membrane providing OH-directed supply. - With the anti-crosstalk design of the acid-blocking anion membrane, the amine regeneration rate is ≥90% and the amine loss rate is ≤10%. It has good operational stability. Through ORP linkage control and bipolar membrane material optimization, after the device has been running continuously for 1000 hours, the transmembrane voltage increase is ≤8% and the water dissociation efficiency remains above 90%.

[0018] The device of the present invention does not require the addition of external acids or alkalis, the amine liquid regeneration rate is ≥90%, the heat-stable salt removal rate is ≥90%, and the high-value salt purity is ≥90%. It solves the problems of serious membrane fouling, low by-product value, and high amine liquid loss rate of existing devices, and is suitable for the treatment of deteriorated amine liquid in fields such as natural gas desulfurization and carbon capture. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the five-chamber bipolar membrane electrodialysis device for purifying deteriorated amine solution according to the present invention. Figure 2 This is a schematic diagram of the pipeline connection structure of the five-chamber bipolar membrane electrodialysis device for purifying deteriorated amine solution according to the present invention. The components are as follows: 1-DC regulated power supply, 2-anode plate, 3-anode chamber, 4-anti-fouling ultrafiltration membrane, 5-pretreatment chamber, 6-anion exchange membrane, 7-amine solution regeneration chamber, 8-bipolar membrane, 9-high-value conversion chamber, 10-cation exchange membrane, 11-raw material salt chamber, 12-acid-resistant anion membrane, 13-cathode chamber, 14-cathode plate, 15-clamping plate, 16-degraded amine solution storage tank, 17-pretreatment solution storage tank, 18-amine solution regeneration storage tank, 19-high-value salt storage tank, 20-raw material salt storage tank, 21-polar solution storage tank, 22-online cleaning module; 23-intelligent monitoring system; 24-variable frequency transfer pump; 25-raw material input port. Detailed Implementation

[0020] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0021] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0022] like Figure 1 and Figure 2 As shown. A five-chamber bipolar membrane electrodialysis device for purifying deteriorated amine solutions includes: an integrated membrane stack ( Figure 1 (2 to 15), Circulating supply system ( Figure 1 (16 to 21) and intelligent monitoring system ( Figure 1 (23, integrated with DC regulated power supply 1). The integrated membrane stack adopts a planar membrane stack structure, and the membrane stack is arranged in the following order: anode plate 2 - anode chamber 3 - antifouling ultrafiltration membrane 4 - pretreatment chamber 5 - anion exchange membrane 6 - amine regeneration chamber 7 - bipolar membrane 8 - high-value conversion chamber 9 - cation exchange membrane 10 - raw material salt chamber 11 - acid-resistant anion membrane 12 - cathode chamber 13 - cathode plate 14. Clamping plates 15 are respectively attached to the outside of the anode plate 2 and the cathode plate 14, and the entire membrane stack is sealed and compressed by the two clamping plates 15 to form a five-functional chamber structure. Among them, the negative side of the bipolar membrane 8 faces the amine regeneration chamber 7, and the positive side faces the high-value conversion chamber 9. The bipolar membrane 8 is a sulfonated covalent organic framework composite bipolar membrane. The circulating supply system includes a degraded amine liquid storage tank 16, a pretreatment liquid storage tank 17, an amine liquid regeneration storage tank 18, a high-value salt storage tank 19, a raw material salt storage tank 20, an extreme liquid storage tank 21, and corresponding transfer pumps for each. The outlet of the degraded amine liquid storage tank 16 is connected to the inlet of the amine liquid regeneration chamber 7, and the inlet of the amine liquid regeneration storage tank 18 is connected to the outlet of the amine liquid regeneration chamber 7, forming a circulation path. The pretreatment liquid storage tank 17 is connected to the pretreatment chamber 5. A circulation path is formed; the high-value salt storage tank 19 is connected to the high-value conversion chamber 9 to form a circulation path; the raw material salt storage tank 20 is connected to the raw material salt chamber 11 to form a circulation path; the outlet of the electrode liquid storage tank 21 is divided into two branches, which are respectively connected to the inlet of the anode chamber 3 and the inlet of the cathode chamber 13. The two branches of the outlet of the anode chamber 3 and the outlet of the cathode chamber 13 merge and are connected to the inlet of the electrode liquid storage tank 21 to form a circulation path; The intelligent monitoring system 23 ( Figure 1 The system (integrated with the DC regulated power supply 1) includes a PLC controller and pH sensors, conductivity sensors and flow sensors respectively installed in the inlet and outlet pipelines of each cavity. The PLC controller is electrically connected to the DC regulated power supply, the PLC control valves of each liquid storage tank, the delivery pump and the pulse generator.

[0023] Furthermore, the five-chamber bipolar membrane electrodialysis device for purifying deteriorated amine solutions also includes an online cleaning module. Figure 1 (22). The online cleaning module 22 is equipped with a cleaning fluid storage tank and a pulse generator; the cleaning fluid storage tank is connected to the degraded amine solution storage tank 16, the pretreatment solution storage tank 17, the high-value salt storage tank 19, the raw material salt storage tank 20, and the extreme liquid storage tank 21 via three-way valves, as shown below. Figure 1 and 2 As shown.

[0024] In addition, to improve the cleaning efficiency of the membrane stack and remove scale buildup, an ultrasonic transducer is embedded inside the membrane stack; preferably, an ultrasonic transducer is embedded inside the anode plate and an ultrasonic transducer is installed inside the cathode plate.

[0025] In the five-chamber bipolar membrane electrodialysis device of the present invention, external raw materials enter and exit the storage tanks through the PLC-controlled valves of each storage tank in the circulation supply system, and the circulation of storage tank-membrane stack-storage tank is realized through the PLC control program.

[0026] The five-chamber bipolar membrane electrodialysis device of the present invention operates as follows: The degraded amine liquid raw material enters the degraded amine liquid storage tank 16 through the raw material input port 25, flows through the liquid outlet below and enters the amine liquid regeneration chamber 7 through the liquid delivery pipeline, and then enters the amine liquid regeneration storage tank 18 after being discharged from the amine liquid regeneration chamber 7. Finally, it is discharged to the external amine liquid storage tank through the liquid outlet of the amine liquid regeneration storage tank 18. The pretreatment liquid raw material enters the pretreatment liquid storage tank 17 through the raw material input port 25, flows through the liquid outlet below and enters the pretreatment chamber 5 through the liquid delivery pipeline, and then is discharged from the pretreatment chamber 5 and returned to the pretreatment liquid storage tank 17 to achieve circulation; High-value salt raw material enters high-value salt storage tank 19 through raw material input port 25, flows through liquid outlet below and into high-value conversion chamber 9 through liquid delivery pipeline, and is then discharged from high-value conversion chamber 9 and returned to high-value salt storage tank 19, thus realizing circulation; The raw salt enters the raw salt storage tank 20 through the raw material input port 25, flows through the liquid outlet below and into the raw salt chamber 11 through the liquid delivery pipe, and then is discharged from the raw salt chamber 11 into the raw salt storage tank 20 to achieve circulation; The electrode liquid raw material enters the electrode liquid storage tank 21 through the raw material input port 25, and then enters the anode chamber 3 and the cathode chamber 13 through the lower outlet via branch lines. After being discharged from the anode chamber 3 and the cathode chamber 13, it returns to the electrode liquid storage tank 21, thus realizing a cycle.

[0027] During the cyclic operation of the electrodialysis unit, all branches containing the online cleaning module 22 are in a closed state.

[0028] The cleaning process of the five-chamber bipolar membrane electrodialysis device of the present invention is as follows: Close raw material input port 25; The cleaning fluid enters the deteriorated amine storage tank 16 from the cleaning fluid storage tank of the online cleaning module 22, flows through the lower outlet and into the amine regeneration chamber 7 via the infusion pipeline, and then is discharged from the amine regeneration chamber 7 and enters the amine regeneration storage tank 18, ensuring that the cleaning fluid fills the entire circulation pipeline and starts the circulation cleaning. The cleaning fluid enters the pretreatment fluid storage tank 17 from the cleaning fluid storage tank of the online cleaning module 22, flows through the lower outlet and into the pretreatment chamber 5 via the delivery pipeline, and then is discharged from the pretreatment chamber 5 and returned to the pretreatment fluid storage tank 17, ensuring that the cleaning fluid fills the entire circulation pipeline and achieves circulation. The cleaning fluid enters the high-value salt storage tank 19 from the cleaning fluid storage tank of the online cleaning module 22, flows through the lower outlet and into the high-value conversion chamber 9 via the delivery pipeline, and then is discharged from the high-value conversion chamber 9 and returned to the high-value salt storage tank 19, ensuring that the cleaning fluid fills the entire circulation pipeline and achieves circulation. The cleaning fluid enters the raw material salt storage tank 20 from the cleaning fluid storage tank of the online cleaning module 22, flows through the liquid outlet below and into the raw material salt chamber 11 via the liquid delivery pipeline, and then is discharged from the raw material salt chamber 11 into the raw material salt storage tank 20, ensuring that the cleaning fluid fills the entire circulation pipeline and finally achieves circulation. The cleaning fluid enters the electrode liquid storage tank 21 from the cleaning fluid storage tank of the online cleaning module 22, and then enters the anode chamber 3 and the cathode chamber 13 through the lower outlet via branch lines. After being discharged from the anode chamber 3 and the cathode chamber 13, it returns to the electrode liquid storage tank 21, ensuring that the cleaning fluid fills the entire circulation pipeline and achieves circulation. After the cleaning fluid fills the entire circulation pipeline, close the valve at the cleaning fluid storage tank of the online cleaning module 22; after 3 to 5 cycles of circulation cleaning, open the valve at the cleaning fluid storage tank to discharge the cleaning fluid into the cleaning fluid storage tank.

[0029] Example 1 A five-chamber bipolar membrane electrodialysis unit was used to treat degraded MDEA amine solution from ship decarbonization. The amine concentration was 15 wt%, the heat-stable salt content was 2.8 wt%, SS was 85 mg / L, and COD was 1200 mg / L. The unit parameters are as follows: Membrane stack configuration: antifouling ultrafiltration membrane (100nm pore size, PVDF-β-cyclodextrin modified), anion exchange membrane (quaternized polyethersulfone, exchange capacity 1.9mmol / g), bipolar membrane (sulfonated COF composite, Zn-Ni ZIF catalyst layer loading 1.0mg / cm³). 2 ), cation exchange membrane (SPEEK, sulfonation degree 70%), acid barrier anion membrane (fluorocarbon resin based).

[0030] A method for purifying deteriorated amine solution, employing a five-chamber bipolar membrane electrodialysis device, includes the following steps: S1. Pretreatment: The degraded amine solution is transported to the pretreatment chamber through the degraded amine solution storage tank. Suspended solids and large molecular organic matter are intercepted by the anti-fouling ultrafiltration membrane, and the permeate enters the amine solution regeneration chamber; the liquid flow rate in each chamber is 20L / h. S2. Amine liquid regeneration: Start the DC regulated power supply, DC voltage 18V, current density 20mA / cm³. 2 In the amine regeneration chamber, thermally stable salt anions migrate through the anion exchange membrane into the high-value conversion chamber, where OH- ions are generated by the dissociation of the bipolar membrane's negative side. - The free amine enters the amine regeneration chamber and reacts with the amine salt to regenerate the amine. The regenerated amine is then recovered from the amine regeneration storage tank. S3. High-value conversion: The high-value cation salt solution (1.0 mol / L lithium chloride solution) in the raw salt storage tank is sent into the raw salt chamber. The cations migrate into the high-value conversion chamber through the cation exchange membrane and combine with the thermally stable salt anions to generate high-value inorganic salts, which are collected by the high-value salt storage tank.

[0031] S4. System maintenance process: When the membrane stack resistance increases by more than 15%, start the online cleaning module and circulate the pulse cleaning fluid for 50 minutes.

[0032] Treatment results: amine regeneration rate 93.7%, heat-stable salt removal rate 91.6%, lithium sulfate purity 95.2%; after 500 hours of continuous operation of the membrane stack, the transmembrane voltage increased from 18V to 18.9V, and the resistance increased by 4.8%.

[0033] Example 2 A five-chamber bipolar membrane electrodialysis unit was used to treat degraded MDEA amine solution from ship decarbonization. The amine concentration was 20 wt%, the heat-stable salt content was 3.1 wt%, SS was 89 mg / L, and COD was 1250 mg / L. The unit parameters are as follows: Membrane stack configuration: antifouling ultrafiltration membrane (100nm pore size, PVDF-β-cyclodextrin modified), anion exchange membrane (quaternized polyethersulfone, exchange capacity 1.9mmol / g), bipolar membrane (sulfonated COF composite, Zn-Ni ZIF catalyst layer loading 1.0mg / cm³). 2 ), cation exchange membrane (SPEEK, sulfonation degree 70%), acid barrier anion membrane (fluorocarbon resin based).

[0034] A method for purifying deteriorated amine solution, employing a five-chamber bipolar membrane electrodialysis device, includes the following steps: S1. Pretreatment: The degraded amine solution is transported to the pretreatment chamber through the degraded amine solution storage tank. Suspended solids and large molecular organic matter are intercepted by the anti-fouling ultrafiltration membrane, and the permeate enters the amine solution regeneration chamber; the liquid flow rate in each chamber is 18L / h. S2. Amine regeneration: Start the DC regulated power supply, DC voltage 18V, current density 22mA / cm². 2In the amine regeneration chamber, thermally stable salt anions migrate through the anion exchange membrane into the high-value conversion chamber, where OH- ions are generated by the dissociation of the bipolar membrane's negative side. - The free amine enters the amine regeneration chamber and reacts with the amine salt to regenerate the amine. The regenerated amine is then recovered from the amine regeneration storage tank. S3. High-value conversion: The high-value cation salt solution (1.0 mol / L lithium chloride solution) in the raw salt storage tank is sent into the raw salt chamber. The cations migrate into the high-value conversion chamber through the cation exchange membrane and combine with the thermally stable salt anions to generate high-value inorganic salts, which are collected by the high-value salt storage tank.

[0035] S4. System maintenance process: When the membrane stack resistance increases by more than 15%, start the online cleaning module and circulate the pulse cleaning fluid for 40 minutes; at the same time, turn on the ultrasonic transducer to assist in descaling.

[0036] Treatment results: amine regeneration rate 90.1%, heat-stable salt removal rate 91.8%, lithium sulfate purity 94.2%; after 500 hours of continuous operation of the membrane stack, the transmembrane voltage increased from 18V to 18.7V, and the resistance increased by 3.9%.

Claims

1. A five-chamber bipolar membrane electrodialysis device for purifying deteriorated amine solutions, characterized in that, include: The integrated membrane stack adopts a planar membrane stack structure, and the membrane stack arrangement is as follows: anode plate - anode chamber - antifouling ultrafiltration membrane - pretreatment chamber - anion exchange membrane - amine regeneration chamber - bipolar membrane - high-value conversion chamber - cation exchange membrane - feed salt chamber - acid-resistant anion membrane - cathode chamber - cathode plate are connected in sequence. Clamping plates are attached to the outside of the anode plate and the cathode plate respectively. The entire membrane stack is sealed and compressed by the two clamping plates to form a five-functional chamber structure. Among them, the negative side of the bipolar membrane faces the amine regeneration chamber and the positive side faces the high-value conversion chamber. The bipolar membrane is a sulfonated covalent organic framework composite bipolar membrane. The circulating supply system includes a degraded amine solution storage tank, a pretreatment solution storage tank, an amine solution regeneration storage tank, a high-value salt storage tank, a raw material salt storage tank, an extreme liquid storage tank, and corresponding transfer pumps for each. The outlet of the degraded amine solution storage tank is connected to the inlet of the amine solution regeneration chamber, and the inlet of the amine solution regeneration storage tank is connected to the outlet of the amine solution regeneration chamber, forming a circulation path. The pretreatment solution storage tank is connected to the pretreatment chamber, forming a circulation path. The high-value salt storage tank is connected to the high-value conversion chamber, forming a circulation path. The raw material salt storage tank is connected to the raw material salt chamber, forming a circulation path. The outlet of the electrode liquid storage tank is divided into two branches, which are respectively connected to the inlets of the anode chamber and the cathode chamber. The two branches of the outlets of the anode chamber and the cathode chamber merge and are connected to the inlet of the electrode liquid storage tank to form a circulation path. The intelligent monitoring system includes a PLC controller and pH sensors, conductivity sensors and flow sensors respectively installed in the inlet and outlet pipelines of each cavity. The PLC controller is electrically connected to a DC regulated power supply, PLC control valves of each liquid storage tank, delivery pumps and pulse generators.

2. The five-chamber bipolar membrane electrodialysis device according to claim 1, characterized in that, The antifouling ultrafiltration membrane is a PVDF-modified charged ultrafiltration membrane with a pore size of 50–200 nm and a surface grafted with β-cyclodextrin groups; the anion exchange membrane is a quaternized polyethersulfone homogeneous membrane with an ion exchange capacity ≥1.8 mmol / g; the acid-barrier anion membrane is a fluorocarbon resin-based modified anion membrane with an acid permeability coefficient ≤0.02 m / h; and the cation exchange membrane is a sulfonated polyethersulfone homogeneous cation exchange membrane with an ion exchange capacity ≥1.5 mmol / g.

3. The five-chamber bipolar membrane electrodialysis device according to claim 1, characterized in that, The pretreatment chamber is equipped with a honeycomb-shaped flow channel mesh with a flow channel width of 2-3 mm, and the surface of the mesh is loaded with a nano-TiO2 photocatalytic coating; the flow channel mesh of the amine regeneration chamber, the high-value conversion chamber and the raw material salt chamber is a rhombic mesh structure with a porosity ≥85%.

4. The five-chamber bipolar membrane electrodialysis device according to claim 1, characterized in that, The intermediate catalyst layer of the bipolar membrane is Zn-Ni bimetallic ZIF-derived porous carbon with a loading of 0.8–1.2 mg / cm³. 2 The cation exchange membrane is a sulfonated polyether ether ketone composite membrane with a sulfonation degree of 60% to 80%.

5. The five-chamber bipolar membrane electrodialysis device according to claim 1, characterized in that, It also includes an online cleaning module.

6. The five-chamber bipolar membrane electrodialysis device according to claim 5, characterized in that, The online cleaning module is equipped with a cleaning fluid storage tank and a pulse generator. The cleaning fluid storage tank is connected to the degraded amine liquid storage tank, the pretreatment liquid storage tank, the high-value salt storage tank, the raw material salt storage tank, and the extreme liquid storage tank through a three-way valve.

7. The five-chamber bipolar membrane electrodialysis device according to claim 5, characterized in that, An ultrasonic transducer is embedded inside the membrane stack.

8. The five-chamber bipolar membrane electrodialysis device according to claim 5, characterized in that, An ultrasonic transducer is embedded inside the anode plate, and an ultrasonic transducer is installed inside the cathode plate.

9. The five-chamber bipolar membrane electrodialysis device according to claim 5, characterized in that, The cleaning solution of the online cleaning module is a mixture of 0.1-0.3 mol / L citric acid and 0.05-0.1 mol / L EDTA. The pulse generator operates at a frequency of 0.5-2 Hz and has a duty cycle of 30%-60%.

10. A method for purifying deteriorated amine solution, characterized in that, The five-chamber bipolar membrane electrodialysis device as described in any one of claims 1 to 5 includes the following steps: S1. Pretreatment: The degraded amine solution is transported to the pretreatment chamber through the degraded amine solution storage tank. The suspended solids and large molecular organic matter are intercepted by the anti-fouling ultrafiltration membrane, and the permeate enters the amine solution regeneration chamber. S2. Amine Regeneration: Start the DC regulated power supply. Thermally stable salt anions in the amine regeneration chamber migrate through the anion exchange membrane into the high-value conversion chamber. OH groups generated by the dissociation of the bipolar membrane anion exchanger... - The free amine enters the amine regeneration chamber and reacts with the amine salt to regenerate the amine. The regenerated amine is then recovered from the amine regeneration storage tank. S3. High-value conversion: The high-value cation salt solution in the raw salt storage tank is sent into the raw salt chamber. The cations migrate into the high-value conversion chamber through the cation exchange membrane and combine with the thermally stable salt anions to generate high-value inorganic salts, which are collected by the high-value salt storage tank.

11. The purification method for treating deteriorated amine solution according to claim 10 further includes the system maintenance process of the five-chamber bipolar membrane electrodialysis device: when the membrane stack resistance increases by more than 15%, the online cleaning module is started, and the pulse cleaning solution is circulated and rinsed for 40 to 60 minutes.

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