Electrodialysis treatment process for high-concentration brine in coal chemical industry

Abstract

The invention discloses an electrodialysis treatment process for coal chemical industry high-concentration brine, and relates to the technical field of water treatment.The electrodialysis treatment process comprises the steps that the coal chemical industry high-concentration brine to be treated is input into a pretreatment module to be treated; conveying the high-concentration brine treated by the pretreatment module to an electrodialysis membrane stack module for treatment through a pressure pump; in the operation process of the electrodialysis membrane stack module, the dynamic flow field management system monitors and regulates fluid dynamic conditions in real time; the enhanced membrane cleaning and regenerating system is used for cleaning and regenerating the electrodialysis membrane stack module; dilute chamber effluent and concentrated chamber effluent treated by the electrodialysis membrane stack module respectively enter a post-treatment and recycling module for deep purification and resource recovery; the whole process flow is subjected to comprehensive real-time monitoring, data analysis, fault diagnosis and optimization control by the central intelligent control system. The invention can realize efficient, stable and economic treatment of high-concentration brine, prolong the service life of the membrane, improve the desalination rate and flux, and ensure reliable operation.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to an electrodialysis treatment process for high-concentration brine in coal chemical industry. Background Technology

[0002] With the vigorous development of modern industrial systems, especially the continuous expansion of the coal chemical industry, the high-concentration brine generated during its production processes has become an increasingly serious environmental governance challenge. This type of wastewater is not only massive in volume, but also, due to its complex composition, extremely high ion concentration, and significant corrosiveness and scaling tendency, places stringent demands on traditional wastewater treatment technologies. Against this backdrop, electrodialysis technology, with its high-efficiency desalination, energy-saving and environmentally friendly properties, and the potential to realize the resource recovery of water and salt, is widely regarded as an important approach to solving the problem of high-concentration brine treatment, and its application value in related industrial fields is increasingly prominent.

[0003] In the development of electrodialysis technology, numerous studies and practices have focused on improving its operational efficiency and equipment reliability. The technical solution published in CN111545070B, at its core, achieves flexible switching between forward and reverse flow states in the electrodialysis unit by cleverly designing the inlet and outlet pipe sections and coordinating the use of inlet and outlet control valves. This design aims to effectively reduce membrane surface scaling through periodic flow reversal, thereby improving the desalination efficiency of the unit to a certain extent. A search of the bipolar membrane electrodialysis unit published in CN109012203B reveals a flexible connection that allows the membrane to be movably connected to the dialysis chamber. This configuration enables the membrane to quickly adjust the pressure difference between adjacent compartments when facing flow fluctuations, effectively reducing the risk of leakage.

[0004] However, with the continuous improvement of water resource recycling efficiency and zero-discharge standards in the coal chemical industry, the flow channel design of the technical solution with publication number CN111545070B, while capable of meeting desalination requirements under ordinary water quality conditions, exhibits significant inadequacy when faced with the high viscosity and extremely high ion concentration characteristics of high-concentration brine from coal chemical processes. When such high-concentration brine flows through the narrow channels of the electrodialysis membrane stack, it easily forms a non-uniform fluid distribution, leading to increased velocity gradients and even local dead zones. This non-uniform fluid dynamic condition directly exacerbates concentration polarization on the membrane surface, hindering efficient ion migration and severely impacting the overall efficiency of electrodialysis. A deeper contradiction lies in the fact that high-concentration brine from coal chemical processes not only contains high concentrations of inorganic salts but is also rich in complex organic matter and various sparingly soluble salts, typically phenolic compounds and calcium sulfate crystals. Although the forward / backflow switching mechanism can alleviate some reversible scaling, its cleaning efficiency is extremely limited in addressing the strong adsorption and dense crystallization of such complex components on the membrane surface. This cleaning method cannot completely remove stubborn pollutants, causing membrane fouling to accumulate continuously, membrane performance to decline, and ultimately leading to a significant reduction in the stability of the equipment operation, a shortened maintenance cycle, and a significant increase in operating costs.

[0005] The technical solution published in CN109012203B employs a flexible connection to address pressure differential changes caused by flow fluctuations, thereby ensuring the membrane stack's sealing performance. This design primarily focuses on the adaptability of mechanical stress under short-term or periodic fluctuations. However, the treatment of high-concentration brine in coal chemical processes often requires higher operating pressures to overcome osmotic pressure differences and maintain sufficient treatment flux. Under long-term, continuous high-pressure operating conditions, the flexible connection design of the membrane may not provide sufficient mechanical strength and structural stability, posing risks of membrane deformation, stress concentration at the connection leading to fatigue failure, and deterioration of sealing performance, ultimately resulting in leakage. This inherent contradiction between mechanical adaptability and long-term high-pressure tolerance becomes particularly prominent in high-concentration brine treatment scenarios. Furthermore, this device does not provide targeted solutions for the highly corrosive components unique to high-concentration brine in coal chemical processes, such as high concentrations of sulfate and chloride ions, as well as the potential chemical corrosion and performance degradation of membrane materials caused by complex organic matter. This lack of adaptability to the chemical properties of the medium directly leads to accelerated membrane fouling, reduced current efficiency, and shortened membrane life, thus affecting the economics and sustainability of the entire treatment process. Summary of the Invention

[0006] The purpose of this invention is to provide an electrodialysis treatment process for high-concentration brine in coal chemical industry, in order to solve the problems faced by existing technologies in treating high-concentration brine in coal chemical industry, such as non-uniform fluid distribution in the flow channel structure, accumulation of stubborn fouling on the membrane surface, insufficient mechanical stability of the membrane stack under high pressure operation, and lack of system integration and optimization.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: An electrodialysis process for treating high-concentration brine in coal chemical industry includes the following core modules and collaborative working mechanisms: The system includes a pretreatment module, an electrodialysis membrane stack module, a dynamic flow field management system, an enhanced membrane cleaning and regeneration system, and a post-treatment and resource recovery module, all integrated, real-time, and adaptively controlled by a central intelligent control system.

[0008] Specifically, the electrodialysis treatment process for high-concentration brine in coal chemical industry includes the following steps: Step S1: High-concentration brine pretreatment. The high-concentration brine from the coal chemical process to be treated is fed into the pretreatment module for processing. The pretreatment module includes a flocculation and sedimentation unit, an advanced oxidation unit, and an ultrafiltration unit.

[0009] The flocculation and sedimentation unit receives high-concentration brine from raw coal chemical processes and precisely adds a composite flocculant of polyaluminum chloride (PAC) and polyacrylamide (PAM) via a metering pump based on real-time water quality analysis results. The concentration range of PAC is 50 to 200 mg / L, and the concentration range of PAM is 2 to 10 mg / L. The addition process is monitored in real time by online turbidity and pH sensors and fed back to the central intelligent control system, which adjusts the dosage and acceleration rate according to preset logic. The flocculation and sedimentation unit is equipped with a rapid mixing zone, a slow mixing zone, and an inclined tube sedimentation zone. The rapid mixing zone uses a mechanical agitator to achieve high-speed mixing at a speed of 100 to 200 rpm and a residence time of 30 to 60 seconds. The slow mixing zone uses a paddle agitator at a speed of 10 to 30 rpm and a residence time of 15 to 30 minutes to promote the full growth of flocs. The inclined tube sedimentation zone uses polypropylene inclined tube packing with a 60-degree angle and a sedimentation time of 2 to 4 hours for efficient solid-liquid separation, removing most suspended solids, colloidal substances, and some large organic molecules. The turbidity of the effluent from the flocculation sedimentation unit is less than 5 NTU.

[0010] The advanced oxidation unit receives the effluent from the flocculation and sedimentation unit. Its function is to deeply degrade recalcitrant organic pollutants such as phenols and polycyclic aromatic hydrocarbons remaining in the high-concentration brine of coal chemical plants, reducing their potential for contamination of the electrodialysis membrane. The advanced oxidation unit uses ultraviolet (UV) / hydrogen peroxide... The process involves a combination of methods. The UV reactor is equipped with a low-pressure ultraviolet lamp with a wavelength of 254 nm and an ultraviolet intensity of 100 to 200 mW / cm². 2 The total power is 20 kW. A 30% (w / w) industrial-grade solution is added to the inlet of the UV reactor using a precision metering pump, with the addition rate controlled at [specific value missing]. The mass ratio of the fluid to chemical oxygen demand (COD) is within the range of 1:1 to 2:1. The UV reactor is internally designed with multiple baffles to ensure a uniform residence time of 10 to 20 minutes within the UV irradiation zone. The advanced oxidation unit achieves a COD removal rate of 30% to 50% in the effluent.

[0011] The ultrafiltration unit receives the effluent from the advanced oxidation unit for further removal of fine suspended solids, residual colloids, bacteria, and large organic molecules, providing high-quality feed water for the electrodialysis membrane stack. The ultrafiltration unit employs a hollow fiber membrane module made of polyvinylidene fluoride (PVDF) with a molecular weight cutoff of 50 to 150 kDa and a pore size of 0.02 to 0.1 micrometers. The ultrafiltration membrane module operates under external pressure with a designed flux of 50 to 80 L / (m³). 2 The ultrafiltration unit is equipped with automatic backwashing and chemical cleaning functions. The automatic backwashing uses membrane permeate water, with a backwash cycle of 30 to 60 minutes, a backwash pressure of 0.1 to 0.2 MPa, and a backwash time of 30 to 60 seconds. The chemical cleaning cycle is 24 to 72 hours, using alternating cleaning with 0.5% sodium hypochlorite solution and 0.2% citric acid solution. The effluent turbidity of the ultrafiltration unit is below 0.5 NTU, and the SDI value is below 4.

[0012] Step S2: Electrodialysis membrane stack treatment. The high-concentration brine treated by the pretreatment module is transported to the electrodialysis membrane stack module via a pressurized pump. The electrodialysis membrane stack module is the core of this invention for achieving efficient desalination, and its structure has been optimized to adapt to the special properties of high-concentration brine from coal chemical processes.

[0013] The electrodialysis membrane stack module includes membrane sheet components, flow channel structure, electrode components, and membrane stack pressurization and support structure.

[0014] The membrane assembly comprises a cation exchange membrane (CEM) and an anion exchange membrane (AEM). The CEM is a sulfonated polyether ether ketone (SPEEK)-based composite membrane with high antioxidant properties and high mechanical strength, having a fixed charge density of 1.5 to 2.0 meq / g and a thickness of 120 to 150 micrometers. The SPEEK-based composite membrane is prepared by casting a SPEEK solution onto a polyester nonwoven fabric support layer to enhance its dimensional stability and compressive strength. The AEM is a quaternized polysulfone (QPS)-based composite membrane with high ion selectivity and high stain resistance, having a fixed charge density of 1.2 to 1.8 meq / g and a thickness of 120 to 150 micrometers. The QPS-based composite membrane is also prepared by casting onto a polyester nonwoven fabric support layer. To further enhance the antifouling performance of the membrane, a superhydrophilic polyethylene glycol (PEG) derivative covalent modification layer is grown in situ on the working surfaces of both the CEM and AEM using plasma polymerization technology. The thickness of the modification layer is 10 to 20 nanometers, which can effectively reduce the adsorption of organic matter and sparingly soluble salts and the tendency to scale.

[0015] The flow channel structure employs a one-piece molded polyphenylene sulfide (PPS) flow channel plate, which possesses excellent corrosion resistance and mechanical strength. The surface of the flow channel plate is etched with periodically distributed diamond-shaped protrusions, the long axis of which forms a 45-degree angle with the main fluid direction. These protrusions are 0.2 mm high and spaced 0.5 mm apart. These diamond-shaped protrusions induce micro-vortices within the narrow intermembrane flow channel, breaking down the fluid boundary layer and significantly reducing concentration polarization. The inlet and outlet of the flow channel plate are designed with a gradually tapered transition to ensure smooth acceleration and deceleration of the fluid as it enters and exits the membrane region, avoiding localized high-speed scouring and turbulent dead zones. The width of the intermembrane flow channel is 0.6 to 0.8 mm to balance pressure drop and mass transfer efficiency.

[0016] The electrode assembly comprises an anode and a cathode. The anode is a size-stabilized anode (DSA) with a titanium substrate coated with a ruthenium oxide-iridium oxide mixed metal oxide coating. The coating thickness is 5 to 10 micrometers, exhibiting excellent electrocatalytic activity and corrosion resistance. The cathode is made of 316L stainless steel plate, with a nickel-molybdenum alloy coating formed on its surface using electrochemical deposition technology to increase its hydrogen evolution overpotential and reduce side reactions. The electrode region is completely isolated from the dilute and concentrated chambers of the membrane stack by a partition and has an independently circulating electrode flushing solution. The electrode flushing solution is a 0.5% (w / w) sodium sulfate solution, circulated by an independent circulation pump at a flow rate controlled at 0.5 to 1.0 L / min to maintain a stable pH value in the electrode region and prevent electrode corrosion and scaling.

[0017] The membrane stack pressurization and support structure is designed to ensure the mechanical stability and sealing reliability of the membrane stack under high-pressure operation. The membrane stack employs a two-end plate clamping structure. The end plates are made of 50 mm thick fiberglass reinforced plastic (FRP) composite material, internally reinforced with multiple layers of cross-fibers, capable of withstanding axial pressures up to 1.1 MPa. The end plates are connected by eight 30 mm diameter 316L stainless steel tie rods, which are pre-tensioned using a hydraulic system. The pre-tensioning force is evenly distributed and precisely controlled at 200 to 300 Newtons per square centimeter to ensure sealing performance between all diaphragms and flow channel plates. The membrane stack is externally designed with an integral frame support structure made of corrosion-resistant coated carbon steel, further enhancing the overall rigidity and seismic resistance of the membrane stack.

[0018] Step S3: Dynamic Flow Field Management. During operation, the electrodialysis membrane stack module is monitored and regulated in real time by the dynamic flow field management system to minimize concentration polarization and membrane fouling.

[0019] The dynamic flow field management system includes a real-time monitoring unit, a fluid control unit, and a dynamic control algorithm.

[0020] The real-time monitoring unit includes multiple high-precision sensors. A four-electrode conductivity sensor, a differential pressure sensor, and an electromagnetic flow meter are installed on the inlet and outlet pipes of the electrodialysis membrane stack, respectively. PT100 temperature sensors and composite pH electrodes are installed at the inlets of the dilute, concentrated, and electrode chambers of the electrodialysis membrane stack, respectively. All sensors acquire data at a frequency of 100 Hz and transmit the data in real-time to the central intelligent control system via the Industrial Ethernet Protocol (PROFINET).

[0021] The fluid control unit includes a variable frequency speed-regulating centrifugal pump and a proportional regulating valve. Both the dilute chamber inlet pump and the concentrate chamber inlet pump are variable frequency speed-regulating centrifugal pumps, with pump bodies made of corrosion-resistant Hastelloy C-276, a maximum head of 50 meters, and a maximum flow rate of 20 m³ / s. 3 The pump speed is precisely controlled by a central intelligent control system with a response time of less than 0.5 seconds. Each branch pipeline is equipped with a pneumatic diaphragm proportional control valve with a PTFE (polytetrafluoroethylene) lining and an adjustment accuracy of ±1%. The fluid control unit also includes a pulse generator, which generates fluid pulses with a frequency of 0.1 to 1 Hz and an amplitude of 10% to 20% of the instantaneous flow rate by periodically changing the local pipeline cross-section or the pump's operating frequency. This further agitates the membrane surface boundary layer and enhances mass transfer.

[0022] The dynamic control algorithm operates on a central intelligent control system, based on a strategy combining model predictive control (MPC) and fuzzy logic. The MPC model, built upon the mass transfer, charge balance, and fluid dynamics equations of the electrodialysis process, can predict in real-time changes in membrane surface concentration polarization and desalination rate. The fuzzy logic algorithm, based on real-time monitored conductivity, pressure difference, and temperature data, and incorporating preset fuzzy rules, adaptively adjusts pump speed, valve opening, and pulse generator operating parameters. For example, when an increase in the conductivity of the dilute chamber effluent and an abnormal increase in the pressure difference between the inlet and outlet of the concentrate chamber are detected, the system will determine that severe concentration polarization or initial scaling exists. The dynamic control algorithm will immediately issue a command to increase the dilute chamber flow rate by 10% to 20% by adjusting the dilute chamber inlet pump speed and the corresponding regulating valve opening, while maintaining a constant total influent flow rate. Simultaneously, the pulse generator will be activated at a frequency of 0.5 Hz for 5 minutes to forcibly disturb the membrane surface. The algorithm aims to minimize energy consumption and maximize operational stability while meeting target desalination and water recovery rates.

[0023] Step S4: Enhanced membrane cleaning and regeneration. To address the persistent organic and inorganic fouling unique to high-concentration brine in coal chemical processes, this invention designs a multi-mode membrane cleaning and regeneration system.

[0024] The enhanced membrane cleaning and regeneration system includes a multi-mode cleaning unit and a membrane regeneration unit.

[0025] The multi-mode cleaning unit includes four modes: hydraulic backwash / forward wash, chemical-enhanced cleaning, electro-flushing, and ultrasonic vibration cleaning. The hydraulic backwash / forward wash is achieved by reversing the flow direction of the inlet and outlet water in the dilute and concentrated chambers. The backwash flow rate is 1.5 to 2.0 times the normal operating flow rate, and the duration is 15 to 30 minutes, used to remove reversible contaminants. The chemical-enhanced cleaning is carried out through a dedicated cleaning fluid circulation system. The cleaning fluid contains a 0.5 M hydrochloric acid solution and a 0.1 M sodium hydroxide and 0.1% sodium dodecyl sulfate (SDS) mixed solution; the hydrochloric acid solution is used to remove inorganic scale, and the 0.1 M sodium hydroxide and 0.1% sodium dodecyl sulfate (SDS) mixed solution is used to remove organic matter and biofilm.

[0026] The cleaning cycle is conducted at a temperature of 50 to 60 °C, with each cleaning step involving a soaking time of 2 to 4 hours and a circulation pump flow rate of 0.5 to 1.0 m / s. The electro-flushing mode involves periodically reversing the DC power polarity of the electrodialysis membrane stack via a central intelligent control system, or applying a square wave pulse current with a frequency of 0.01 to 0.1 Hz. The polarity reversal time is 1 to 5 minutes, and the pulse current density is 10 to 20 A / m. 2This ultrasonic vibration cleaning unit utilizes an electric field to remove charged contaminants. Multiple high-frequency ultrasonic transducers are integrated outside the electrodialysis membrane stack, operating at a frequency of 30 to 40 kHz with a total power of 500 W. The transducers generate ultrasonic waves through the piezoelectric effect, creating cavitation and acoustic flow effects in the liquid. These effects, along with mechanical vibration and micro-jet flow, assist in the removal of stubborn scale and adsorbates from the membrane surface. The ultrasonic vibration cleaning can be periodically activated during electrodialysis operation, lasting 5 to 10 minutes each time.

[0027] The membrane regeneration unit is used for deep activation of the membrane sheets when membrane performance is severely degraded. The membrane regeneration process includes alternating high-concentration acid-base immersion and electric field-assisted regeneration. First, the membrane stack is immersed in a 4 M HCl solution for 24 hours, followed by rinsing with pure water. Subsequently, it is immersed in a 4 M NaOH solution for 24 hours, and then rinsed with pure water again. During this period, a low-intensity electric field of 0.5 V / cm is applied across the membrane stack to accelerate ion migration and contaminant desorption, thereby restoring the membrane's ion exchange capacity and permeation performance.

[0028] Step S5: Post-treatment and resource recovery. The dilute and concentrated effluents from the electrodialysis membrane stack module are respectively sent to the post-treatment and resource recovery module for further purification and resource recovery.

[0029] The post-processing and resource utilization module includes a freshwater deep purification unit and a concentrated water crystallization unit.

[0030] The deep desalination unit receives effluent from the electrodialysis dilution chamber and aims to produce industrial reuse or discharge water that meets specific standards. The unit includes a reverse osmosis (RO) membrane module and a polished ion exchange column. The RO membrane module uses a high-desalination-rate composite polyamide membrane, designed for a desalination rate of over 98% and an operating pressure of 4 to 6 MPa. A security filter with a 5-micron polypropylene filter element is installed before the RO membrane module to prevent damage to the RO membrane from fine particulate matter. The polished ion exchange column is filled with a strongly acidic cation exchange resin and a strongly basic anion exchange resin to remove trace ions remaining in the water, ensuring that the resistivity of the produced water reaches over 10 MΩ·cm, meeting the requirements for high-purity water.

[0031] The concentrated water crystallization unit receives the effluent from the electrodialysis concentrate chamber, aiming to achieve the recovery and crystallization of high-concentration salts. The unit includes a multi-effect evaporator and a forced circulation crystallizer. The multi-effect evaporator employs a triple-effect falling film evaporation process, with a first-effect operating temperature of 120 °C, achieving a final concentration ratio of 5 to 8 times, further concentrating the salts in the concentrate. The evaporator is made of corrosion-resistant titanium alloy (Ti-Gr2) to withstand high-salt and high-temperature environments. The forced circulation crystallizer receives the evaporator concentrate, maintains the saturation temperature through a steam-heated jacket, and uses a circulating pump to force-circulate the slurry, inducing salt crystallization under conditions where the supersaturation is controlled between 1.05 and 1.10. The crystallizer is internally designed with a crystal slurry separator; the crystallized salt is discharged from the bottom and undergoes solid-liquid separation by a centrifugal dewatering machine, producing industrial-grade sodium chloride and sodium sulfate crystals with a water content of less than 5%. The centrifugal dewatering machine is a horizontal screw discharge sedimentation centrifuge with a rotation speed of 3000 rpm.

[0032] Step S6: Central Intelligent Control. The entire process is comprehensively monitored in real time, with data analysis, fault diagnosis, and optimized control performed by the Central Intelligent Control System (CICS).

[0033] The central intelligent control system consists of a hardware architecture and a software architecture. The hardware architecture includes a Siemens S7-1500 series dual-redundant programmable logic controller (PLC), equipped with a main processor module CPU 1518-4 PN / DP and a fail-safe module to ensure system stability and reliability. The PLC communicates at high speed with field distributed I / O modules, HMI (Human Machine Interface) workstations, sensors, and actuators via PROFINET industrial Ethernet. The HMI workstation uses an industrial-grade touchscreen PC pre-installed with SCADA (Supervisory Control and Data Acquisition) software for real-time visualization of the process flow, parameter setting, and alarm management.

[0034] The software architecture comprises a SCADA system, an Advanced Process Control (APC) layer, and a database management system. The SCADA system is responsible for real-time data acquisition, equipment status monitoring, alarm management, and operator interaction. The APC layer deploys adaptive control algorithms, predictive maintenance algorithms, and energy optimization algorithms. The adaptive control algorithm adjusts the current density, voltage, and flow rate of the electrodialysis membrane stack in real time based on data provided by online water quality analyzers (e.g., online ion chromatographs monitoring Cl-, SO42-, Na+, and Ca2+ concentrations, and online total organic carbon (TOC) analyzers monitoring organic matter concentrations) to adapt to fluctuations in influent water quality and concentration. The predictive maintenance algorithm utilizes historical operating data and machine learning models to predict membrane fouling trends and the lifespan of equipment components, issuing maintenance alerts in advance and generating maintenance plans, thereby significantly reducing unplanned downtime. The energy optimization algorithm comprehensively considers factors such as the desalination rate, water recovery rate, DC power consumption, and pump power consumption of the electrodialysis process, dynamically adjusting the operating parameters of the entire process to achieve the lowest overall energy consumption per unit volume of treated water. The database management system uses an SQL Server database to store all sensor data, operation logs, alarm records, and maintenance history data, providing data support for system analysis and optimization.

[0035] Compared with the prior art, the beneficial technical effects of the present invention are as follows: The enhanced pretreatment module employed in this invention can target and remove high levels of suspended solids, complex organic matter, and specific sparingly soluble salts from high-concentration brine in coal chemical processes, significantly reducing the contamination load entering the electrodialysis membrane stack. This ensures the long-term, stable, and efficient operation of the electrodialysis membrane, effectively extending membrane life and reducing cleaning frequency, thereby reducing operating and maintenance costs.

[0036] The electrodialysis membrane assembly designed in this invention possesses high corrosion resistance and antifouling properties in its membrane material and surface modification. The flow channel plate employs a periodic rhomboid protrusion structure, which effectively induces micro-eddies, enhances the mass transfer process, and significantly reduces concentration polarization under the conditions of high-concentration brine, high viscosity, and high ion concentration in coal chemical processes. This enables the electrodialysis process to operate stably at higher current densities, thereby significantly improving desalination efficiency and throughput.

[0037] The membrane stack pressurization and support structure designed in this invention employs FRP composite end plates and hydraulic pre-tensioning rods, providing uniform and stable high-pressure support. This structure ensures the long-term mechanical stability of the membrane stack under high operating pressure, effectively avoiding membrane deformation, stress concentration at joints, and leakage risks, thus guaranteeing the operational reliability of the device.

[0038] The dynamic flow field management system introduced in this invention monitors key operating parameters in real time using high-precision sensors and performs precise and adaptive control of flow rate, pressure, and fluid pulses based on MPC and fuzzy logic algorithms. This system can respond to changes in operating conditions in real time, actively suppress concentration polarization, maximize ion migration efficiency, and further improve the operating performance and stability of the electrodialysis device.

[0039] The enhanced membrane cleaning and regeneration system provided by this invention includes four modes: hydraulic backwashing / forward washing, chemically enhanced cleaning, electro-flushing, and ultrasonic vibration cleaning, as well as a high-concentration acid-alkali alternating immersion and electric field-assisted regeneration strategy. This multi-mode cleaning and regeneration scheme can target and thoroughly remove the organic adsorption, inorganic scaling, and biological contamination unique to high-concentration brine in coal chemical processes, effectively restoring membrane performance, significantly extending membrane lifespan, and reducing membrane replacement frequency.

[0040] This invention integrates an electrodialysis membrane stack with enhanced pretreatment, deep desalination, and concentrated water crystallization modules, and performs comprehensive, real-time optimization control through a central intelligent control system. This integrated design achieves synergistic effects among the units, reducing pollution at the source, optimizing desalination in the middle stage, and realizing resource recovery at the end, thus forming a complete zero-discharge or resource recovery solution for high-concentration brine, meeting the stringent environmental protection and sustainable development requirements of the coal chemical industry. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the system flow of the electrodialysis treatment process for high-concentration brine in coal chemical industry according to the present invention; Figure 2 This is a schematic diagram of the electrodialysis membrane stack module of the present invention. Detailed Implementation

[0042] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely intended to explain the present invention and not to limit the present invention. For those skilled in the art, the present invention can be practiced without some of these specific details. The following description of the embodiments is merely to provide a better understanding of the present invention by illustrating examples of the invention.

[0043] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0044] In the embodiments of the present invention, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of the present invention shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on the present invention; the term "multiple" in the present invention refers to two or more (including two).

[0045] This invention provides an electrodialysis process for treating high-concentration brine in coal chemical industries. It aims to offer an integrated, efficient, and sustainable technical solution to the complex operating conditions faced by the coal chemical industry when treating high-concentration brine. Specifically, it systematically optimizes and improves upon the inherent challenges of traditional electrodialysis technology in terms of membrane fouling, concentration polarization, mechanical stability, and system integration. Through sophisticated pretreatment, optimized electrodialysis membrane stacks, dynamic flow field management, multi-mode membrane cleaning and regeneration, and an integrated post-treatment and resource recovery module, all under the coordination of a central intelligent control system, this invention achieves efficient desalination and resource utilization of high-concentration brine from coal chemical processes.

[0046] Specifically, the electrodialysis treatment process for high-concentration brine in coal chemical industry of the present invention covers six core modules and their synergistic operation mechanism.

[0047] Step S1: Pretreatment with high-concentration brine.

[0048] The high-concentration brine from coal chemical plants to be treated typically exhibits the following water quality characteristics: high suspended solids (TSS), high chemical oxygen demand (COD), high turbidity, high total dissolved solids (TDS), and a pH fluctuating between 6.5 and 8.5. The temperature range is usually 20 to 45°C. This brine is first fed into a pretreatment module for further processing. Specifically, the TSS is typically 200 to 1000 mg / L; COD is generally higher than 500 mg / L, and in some cases even exceeds 2000 mg / L. It contains complex organic matter such as phenols, polycyclic aromatic hydrocarbons (PAHs), and heterocyclic compounds. The high turbidity ranges from 50 to 500 NTU, and the TDS can reach 20,000 to 80,000 mg / L. The main ions include sodium (Na₂O₃). + Cl - SO4 2- Ca 2+ Mg 2+ wait.

[0049] The pretreatment module (1) serves as the "outpost" of the entire process. Its function is to reduce the pollution load in the raw water to the greatest extent possible, providing high-quality feed water for the subsequent electrodialysis membrane stack module (2), thereby effectively extending the service life of the membrane and ensuring operational stability. The pretreatment module (1) has a sophisticated internal structure, specifically including a flocculation sedimentation unit (7), an advanced oxidation unit (8), and an ultrafiltration unit (9).

[0050] The flocculation and sedimentation unit (7) is the first step in the pretreatment module. Its main task is to efficiently remove suspended solids, colloidal substances, and some macromolecular organic matter from the raw water. The unit receives high-concentration brine from the original coal chemical plant and, based on real-time data fed back by the online water quality analyzer, the central intelligent control system (6) instructs a precision metering pump to accurately add a composite flocculant of polyaluminum chloride (PAC) and polyacrylamide (PAM). PAC, usually basic aluminum chloride, is added in the form of a 10% mass concentration aqueous solution through a metering pump. Its effective addition concentration range is precisely controlled between 50 and 200 mg / L, aiming to provide the main charge neutralization and adsorption bridging effects.

[0051] PAM, usually anionic polyacrylamide with a molecular weight of 8 million to 12 million, is added in the form of a 0.1% mass concentration dilute solution. Its effective addition concentration range is 2 to 10 mg / L. Its main function is to enhance the growth and sedimentation of flocs. The dosage and acceleration rate of flocculant are adjusted by online turbidity and pH sensors in real time and fed back to the central intelligent control system (6). The system adaptively adjusts the dosing pump according to the preset PID control logic and fuzzy control strategy to ensure the best flocculation effect. The internal space of the flocculation sedimentation unit is divided into three functional areas: a fast mixing zone, a slow mixing zone and an inclined tube sedimentation zone. The fast mixing zone is designed as a small mixing tank with a mechanical stirrer. The stirring blades are made of 316L stainless steel and driven by a variable frequency motor to achieve high-speed stirring of 100 to 200 rpm. This ensures that the flocculant and raw water are rapidly and uniformly mixed within a very short residence time of 30 to 60 seconds, which promotes the rapid collision of tiny colloidal particles and the formation of primary flocs. The slow mixing zone employs a paddle mixer with low-shear blades and a stirring speed controlled at 10 to 30 rpm, providing a longer residence time of 15 to 30 minutes. This aims to provide a gentle shear environment for the primary flocs, promoting their full growth and forming dense, easily settling secondary flocs. The inclined tube sedimentation zone is the core of solid-liquid separation. It is filled with 60-degree angled polypropylene (PP) inclined tube packing material, with channel dimensions of 50mm × 50mm and a wall thickness of 1mm. The inclined angle and channel design of the inclined tubes effectively shorten the settling distance of particles and increase the effective sedimentation area, enabling efficient solid-liquid separation of the flocs within a 2 to 4-hour sedimentation time. This removes most suspended solids, colloidal substances, and some large organic molecules. The effluent turbidity of this unit can be stably controlled below 5 NTU, providing a good water quality foundation for subsequent advanced oxidation treatment.

[0052] The advanced oxidation unit (8) receives the effluent from the flocculation and sedimentation unit. Its main function is to deeply degrade recalcitrant organic pollutants such as phenols and polycyclic aromatic hydrocarbons that remain in the high-concentration brine of coal chemical plants and are difficult to remove by conventional physicochemical methods, significantly reducing their potential pollution to the electrodialysis membrane. The combined process utilizes the strong oxidizing effect of hydroxyl radicals (·OH) to degrade pollutants. The UV reactor adopts a closed 316L stainless steel chamber design, equipped with low-pressure UV lamps with a total power of 20kW. Each lamp has a wavelength of 254nm, and the UV intensity on the lamp surface can reach 100 to 200mW / cm². 2 These lamps are isolated from the water by quartz sleeves and are equipped with an automatic cleaning device to keep the surface of the quartz sleeves clean and ensure effective penetration of ultraviolet light.

[0053] A 30% (w / w) industrial-grade solution is stored in a ventilated PE tank and precisely added to the inlet of the UV reactor via a corrosion-resistant precision metering pump. The dosage is controlled within a 1:1 to 2:1 mass ratio of H2O2 to COD based on real-time data from an online COD analyzer to ensure sufficient hydroxyl radical generation. The UV reactor is cleverly designed with multiple PTFE baffles, forming a meandering flow path to ensure uniform residence time distribution of the fluid within the UV irradiation zone, avoiding short-circuiting and dead zones; the residence time is controlled to 10 to 20 minutes. Through this advanced oxidation process, the effluent COD removal rate can stably reach 30% to 50%, significantly reducing the organic pollution load.

[0054] The ultrafiltration unit (9) receives the effluent from the advanced oxidation unit. Its function is to further remove fine suspended solids, residual colloids, bacteria, and macromolecular organic matter, providing high-quality ultrapure water that meets stringent feed water requirements for the electrodialysis membrane stack. The ultrafiltration unit uses hollow fiber membrane modules, and the membrane material is polyvinylidene fluoride (PVDF), which is favored for its excellent chemical stability and hydrophilicity. The membrane has a molecular weight cutoff of 50 to 150 kDa and a pore size controlled between 0.02 and 0.1 micrometers, enabling efficient removal of microorganisms and fine particles. The ultrafiltration membrane module adopts an external pressure operation mode, where the raw water flows on the outside and the permeate is collected from the inner cavity of the membrane. This mode is beneficial for treating water bodies with high suspended solids and facilitates backwashing and cleaning. The designed membrane flux is 50 to 80 L / (m²). 2 •h), ensuring water quality while also considering membrane lifespan.

[0055] To maintain long-term stable membrane operation, the ultrafiltration unit is equipped with comprehensive automatic backwashing and chemical cleaning functions. Automatic backwashing is performed periodically, typically every 30 to 60 minutes, using membrane permeate as the backwash solution. The backwash pressure is controlled at 0.1 to 0.2 MPa, and the backwash time is 30 to 60 seconds, removing reversible contaminants accumulated on the membrane surface through a momentary reverse water flow impact. In addition, the system also has a periodic chemical cleaning function, with a cleaning cycle of 24 to 72 hours. Cleaning is performed using a CIP (Clean-in-Place) system, alternately using a 0.5% sodium hypochlorite solution (adjusted to pH 10-11) and a 0.2% citric acid solution (adjusted to pH 2-3) to remove organic and inorganic scale, respectively. The ultrafiltration unit effluent turbidity is below 0.5 NTU, and the Silt Density Index (SDI) value is below 4, fully meeting the feed water requirements of the electrodialysis membrane stack and significantly reducing the risk of membrane fouling.

[0056] Step S2: Electrodialysis membrane stack treatment.

[0057] The high-concentration brine treated by the pretreatment module is then filtered through a precision filter and transported to the electrodialysis membrane stack module (2) by a corrosion-resistant pressurized pump. The electrodialysis membrane stack module is the core of this invention for achieving efficient desalination. Its structure has been optimized to adapt to the special properties of high-concentration brine in coal chemical industry, such as high salinity, high organic matter, and easy scaling, ensuring stable operation under high current density. The electrodialysis membrane stack module (2) includes a membrane assembly (10), a flow channel structure (11), an electrode assembly (12), and a membrane stack pressurization and support structure (13).

[0058] The membrane module (10) is the cornerstone of the electrodialysis membrane stack, and its performance directly determines the desalination efficiency and antifouling capability. The membrane module includes a cation exchange membrane (CEM) and an anion exchange membrane (AEM), both of which adopt a composite membrane structure to balance performance and mechanical strength. The CEM uses a sulfonated polyether ether ketone (SPEEK)-based composite membrane with high antioxidant properties and high mechanical strength. SPEEK is used as the membrane substrate, and its degree of sulfonation is precisely controlled to achieve a fixed charge density range of 1.5 to 2.0 meq / g, ensuring efficient cation selective migration. The membrane thickness is controlled at 120 to 150 micrometers. To enhance the dimensional stability and compressive strength of the membrane, the SPEEK-based composite membrane is prepared by solution casting, in which the SPEEK solution is uniformly cast onto a polyester nonwoven fabric support layer and cured by precise solvent evaporation and heat treatment processes. This composite structure effectively avoids the swelling and deformation that may occur in pure SPEEK membranes during operation. The AEM employs a quaternized polysulfone (QPS)-based composite membrane with high ion selectivity and high fouling resistance. The QPS achieves a fixed charge density of 1.2 to 1.8 meq / g through precise control of its quaternization degree, enabling efficient anion-selective migration and effectively suppressing co-ion transport. The thickness of the AEM is also controlled within 120 to 150 micrometers. The QPS-based composite membrane is also prepared by solution casting onto a polyester nonwoven fabric support layer, thus imparting the necessary mechanical strength and stability. To further enhance the membrane's antifouling performance, a superhydrophilic polyethylene glycol (PEG) derivative covalent modification layer is grown in situ on the working surfaces of both the CEM and AEM using plasma polymerization technology. This modification layer is formed on the membrane surface as a highly cross-linked hydrophilic coating using monomers such as PEG-methacrylate as precursors in a radio frequency plasma reactor. The thickness of the modification layer is precisely controlled between 10 and 20 nanometers. By reducing the hydrophobicity of the membrane surface, the coverage of water molecules on the membrane surface is effectively increased, thereby significantly reducing the adsorption of organic matter and the scaling tendency of sparingly soluble salts, and improving the membrane's antifouling ability at the molecular level.

[0059] The flow channel structure (11) is crucial to the performance of the electrodialysis membrane stack, and its design directly affects the uniformity of fluid distribution, mass transfer efficiency, and pressure drop. This invention uses a one-piece molded polyphenylene sulfide (PPS) flow channel plate. PPS material, with its excellent corrosion resistance, high temperature stability, and high mechanical strength, is particularly suitable for the harsh environment of high-concentration brine in coal chemical industry. The flow channel plate is manufactured by precision injection molding to ensure dimensional accuracy and structural stability. Its unique feature is that the surface of the flow channel plate is cleverly etched with periodically distributed rhomboid protrusions. The long axis of the rhomboid protrusions forms a 45-degree angle with the main fluid direction (the direction of the dilute / concentrate chamber inlet), with a height of 0.2 mm and a spacing of 0.5 mm. This rhomboid protrusion structure can effectively induce the generation of micro-vortices in the narrow inter-membrane flow channel (the width of the inter-membrane flow channel is 0.6 to 0.8 mm), locally disturb the fluid, break the boundary layer stagnation zone that is easily formed by conventional mesh partitions, and significantly reduce concentration polarization. Computational fluid dynamics (CFD) simulations show that this structure can improve the membrane surface mass transfer coefficient by more than 20%. Furthermore, the inlet and outlet of the flow channel plate are designed with a gradually tapered transition structure to ensure smooth acceleration and deceleration of the fluid as it enters and exits the membrane region, avoiding membrane damage caused by localized high-speed scouring and uneven fluid distribution caused by turbulent dead zones. The 0.6 to 0.8 mm inter-membrane flow channel width is the result of meticulous optimization, aiming to balance the pressure drop loss during fluid flow with the improvement in mass transfer efficiency, ensuring optimal desalination performance with reasonable energy consumption.

[0060] The electrode assembly (12) is the driving core of the electrodialysis process, and its stability and efficiency directly affect the long-term operation of the entire system. The electrode assembly includes an anode and a cathode, and its materials and coatings are specially optimized to cope with the complex medium of high-concentration brine in coal chemical industry. The anode adopts a dimensionally stable anode (DSA), and its substrate is industrial pure titanium metal (ASTM B265 Grade 1). After strict surface treatment, the surface is coated with a ruthenium oxide-iridium oxide (RuO2-IrO2) mixed metal oxide coating with a thickness of 5 to 10 micrometers (typical ratio of RuO2 70wt%, IrO2 30wt%). This coating is prepared by thermal decomposition or electrochemical deposition and has excellent electrocatalytic activity, which can efficiently carry out the oxygen evolution reaction. At the same time, it exhibits excellent corrosion resistance in chlorine-rich environments, ensuring the stability of the anode under long-term high current density operation. The cathode uses 316L stainless steel plate as the substrate. 316L stainless steel is selected due to its excellent corrosion resistance. A nickel-molybdenum (Ni-Mo) alloy coating is formed on its surface using advanced electrochemical deposition technology. This coating significantly improves the hydrogen evolution overpotential and effectively suppresses hydrogen evolution side reactions, thereby enhancing current efficiency and reducing electrode corrosion and energy consumption. To prevent side reaction products generated in the electrode area from affecting membrane stack performance, the electrode area is completely isolated from the dilute and concentrated chambers of the membrane stack by dense polypropylene partitions and EPDM gaskets. Furthermore, the electrode area is equipped with an independent circulating flushing fluid system. The electrode flushing fluid is a 0.5% (w / w) sodium sulfate (Na₂SO₄) solution, circulated by an independent corrosion-resistant magnetically driven circulation pump with a flow rate precisely controlled between 0.5 and 1.0 L / min. This flushing fluid system monitors the pH value of the electrode area using an online pH sensor and can automatically add dilute sulfuric acid or dilute sodium hydroxide solution to maintain a stable pH value of 6.0 to 8.0, effectively preventing electrode corrosion, scaling, and chlorine gas escape, ensuring long-term stable operation of the electrode assembly.

[0061] The membrane stack pressurization and support structure (13) is designed to ensure the mechanical stability, structural integrity, and sealing reliability of the electrodialysis membrane stack under high-pressure operating conditions. The membrane stack adopts a structure design with end plates clamped at both ends to provide uniform axial pressure. The end plates are made of 50 mm thick fiberglass (FRP) composite material, internally reinforced with multi-layer cross-fibers. Through precise fiber layup design and vacuum-assisted resin infusion process, it ensures an axial pressure resistance of up to 1.1 MPa and excellent corrosion resistance and insulation. The two end plates are connected by eight 30 mm diameter 316L stainless steel tie rods with precision-machined threads and pre-tightened by a hydraulic system. The hydraulic system monitors the force on each tie rod in real time through high-precision pressure sensors. The pre-tightening force is evenly distributed and can be precisely controlled at a clamping force of 200 to 300 Newtons per square centimeter to ensure a reliable and leak-free seal between all membranes and flow channel plates, maintaining their integrity even under long-term high-pressure operation. The membrane stack has an integrated frame support structure on the outside, made of corrosion-resistant coated carbon steel. It is connected by welding and bolts to form a high-rigidity skeleton, which further enhances the overall rigidity and seismic resistance of the membrane stack, effectively resists the vibration and stress generated during operation, and ensures the reliability of the equipment in industrial environments.

[0062] Step S3: Dynamic flow field management.

[0063] During operation, in order to suppress concentration polarization and membrane fouling to the greatest extent and optimize energy consumption, the electrodialysis membrane stack module is monitored and controlled in real time by the dynamic flow field management system (3).

[0064] The dynamic flow field management system (3) is built on a sophisticated sensor network, efficient actuators and intelligent control algorithms, and includes a real-time monitoring unit (14), a fluid control unit (15) and a dynamic control algorithm (16).

[0065] The real-time monitoring unit (14) is equipped with a variety of high-precision sensors to collect key process parameters. High-precision four-electrode conductivity sensors are installed on the inlet and outlet water pipes of the dilute and concentrate chambers of the electrodialysis membrane stack to monitor changes in ion concentration in the water in real time. This is a key indicator for assessing desalination rate and concentration polarization. Simultaneously, differential pressure transmitters are installed at the inlet and outlet on both sides of the membrane stack to monitor the pressure drop of the membrane stack in real time. This is a direct indication of membrane fouling and flow channel blockage. Furthermore, electromagnetic flowmeters accurately measure the inlet and outlet water flow rates of the dilute and concentrate chambers, providing a basis for water recovery rate calculation and flow rate control. PT100 high-precision temperature sensors and composite pH electrodes are installed at the inlets of the dilute, concentrate, and electrode chambers of the electrodialysis membrane stack to monitor water temperature and pH value. These parameters have a significant impact on ion migration rate, membrane resistance, and potential scaling. All sensor data acquisition frequencies are set to 100Hz and transmitted in real time and at high speed to the PLC of the central intelligent control system (6) via the Industrial Ethernet Protocol (PROFINET) to ensure that the control system can obtain the most timely process information.

[0066] The fluid control unit (15) is the actuator for dynamic flow field management. It includes a variable frequency speed-regulating centrifugal pump and a proportional regulating valve, which can precisely control the flow rate and pressure of the fluid. Both the dilute chamber inlet pump and the concentrated chamber inlet pump are variable frequency speed-regulating centrifugal pumps, and their pump bodies are made of corrosion-resistant Hastelloy C-276 to cope with the corrosiveness of high-concentration brine. These pumps have a maximum head of 50 meters and a maximum flow rate of 20 m³ / h. 3 / h. The pump speed is precisely controlled by a 0-10V or 4-20mA analog signal from the central intelligent control system (6). The frequency converter has a response time of less than 0.5 seconds, ensuring rapid response of flow rate regulation. Pneumatic diaphragm proportional regulating valves are installed on each branch pipeline. The valve body is lined with polytetrafluoroethylene (PTFE) to provide excellent corrosion resistance. The valve regulation accuracy is ±1%. These regulating valves are connected to the analog output module of the PLC and achieve fine regulation of flow or pressure through PID control. In addition, the fluid control unit (15) also includes an innovative pulse generator, which generates fluid pulses with a frequency of 0.1 to 1Hz and an amplitude of 10% to 20% of the instantaneous flow rate by periodically changing the local pipeline cross section or the pump operating frequency. This pulse flow can effectively induce micro-eddies and shear forces on the membrane surface, further disturb the membrane surface boundary layer, enhance ion mass transfer, and effectively suppress concentration polarization.

[0067] The dynamic control algorithm (16) is the "brain" of the dynamic flow field management system. It runs on the PLC (Siemens S7-1500 series) of the central intelligent control system (6) and adopts an advanced strategy of model predictive control (MPC) combined with fuzzy logic. The MPC model is based on the mass transfer dynamics (Nernst-Planck equation, intermembrane fluid diffusion model), charge balance and fluid dynamics equations (Navier-Stokes equation combined with porous media model) of the electrodialysis process. It can use real-time monitoring data to predict the concentration polarization degree inside the membrane stack, the ion concentration distribution on the membrane surface, and key performance indicators such as desalination rate and energy consumption. The fuzzy logic algorithm adaptively adjusts the pump speed, valve opening and pulse generator operating parameters based on real-time monitored conductivity, pressure difference and temperature data, combined with expert experience and preset fuzzy rules, in order to cope with complex changes in operating conditions.

[0068] When the system detects an abnormally high conductivity in the dilute chamber effluent and a short-term abnormal increase in the pressure difference between the inlet and outlet of the concentrate chamber, the dynamic control algorithm will immediately determine that there is a severe mass transfer obstruction. At this point, the system will issue instructions based on fuzzy rules to increase the dilute chamber flow rate by 10% to 20% by adjusting the dilute chamber inlet pump speed and the opening of the corresponding regulating valve, while maintaining a constant total influent flow rate. This enhances the shear force on the membrane surface. Simultaneously, a pulse generator is activated and runs continuously at a frequency of 0.5 Hz for 5 minutes to generate strong fluid disturbances, forcibly stripping the concentration polarization layer or initial deposits from the membrane surface. The ultimate goal of the algorithm is to minimize the total system energy consumption and maximize the long-term operational stability of the electrodialysis unit by continuously optimizing operating parameters, while meeting the target desalination rate and water recovery rate.

[0069] Step S4: Enhanced membrane cleaning and regeneration.

[0070] To effectively address the complex pollution types unique to high-concentration brine in coal chemical processes, such as stubborn organic adsorption, inorganic salt scaling, and biofilm formation, this invention specifically designs a multi-mode, all-round enhanced membrane cleaning and regeneration system (4). This system aims to maximize membrane performance recovery, extend membrane lifespan, and reduce operating and maintenance costs. The enhanced membrane cleaning and regeneration system (4) includes a multi-mode cleaning unit (17) and a membrane regeneration unit (18).

[0071] The multi-mode cleaning unit (17) integrates four modes: hydraulic backwash / forward wash, chemical enhanced cleaning, electroflushing, and ultrasonic vibration cleaning, which can be flexibly combined according to the type and degree of fouling. The hydraulic backwash / forward wash mode controls the automatic valve group through the central intelligent control system (6) to reverse the flow direction of the inlet and outlet water in the dilute and concentrate chambers, thereby achieving physical flushing of the membrane stack. The backwash flow rate is usually set to 1.5 to 2.0 times the normal operating flow rate, and the duration is 15 to 30 minutes. Its main function is to remove reversible contaminants accumulated on the membrane surface and loose particles in the flow channel. Chemical enhanced cleaning is carried out through a dedicated cleaning fluid circulation system. This system includes a corrosion-resistant cleaning fluid storage tank, a heating coil, a chemical metering pump, and a corrosion-resistant circulation pump. The cleaning solution is selected according to the nature of the fouling: for inorganic scale, a 0.5M hydrochloric acid (HCl) solution is used to dissolve scale such as carbonates and sulfates; for organic matter and biofilm, a mixed solution of 0.1M sodium hydroxide (NaOH) and 0.1% sodium dodecyl sulfate (SDS) is used, where NaOH is used to saponify organic matter and hydrolyze biofilm, and SDS, as an anionic surfactant, has excellent wetting, dispersing and solubilizing effects. The cleaning cycle is carried out at a set temperature, and each cleaning step includes a soaking time of 2 to 4 hours, followed by a circulating flush at a flow rate of 0.5 to 1.0 m / s using a circulating pump to ensure that the cleaning solution is in full contact with the membrane surface. The electro-flushing mode uses the physical effect of the electric field to remove charged contaminants. The central intelligent control system (6) periodically reverses the polarity of the DC power supply of the electrodialysis membrane stack, or applies a square wave pulse current with a frequency of 0.01 to 0.1 Hz and a pulse current density of 10 to 20 A / m 2 The time for reversing polarity is typically 1 to 5 minutes. By changing the direction and intensity of the electric field, the electric field force, electrophoresis, and electroosmosis effects can be used to detach charged contaminants adsorbed on the membrane surface. The ultrasonic vibration cleaning unit integrates multiple high-frequency ultrasonic transducers outside the electrodialysis membrane stack, with an operating frequency of 30 to 40 kHz and a total power of 500 W. The transducers convert electrical energy into mechanical energy through the piezoelectric effect, generating high-frequency vibrations in the liquid and forming tiny cavitation bubbles. When these bubbles burst, they generate powerful microjets and shock waves, using mechanical vibration and cavitation effects to assist in the removal of stubborn scale and adsorbates from the membrane surface. Ultrasonic vibration cleaning can be periodically activated during electrodialysis operation, lasting 5 to 10 minutes each time, achieving online and dynamic suppression of membrane fouling.

[0072] The membrane regeneration unit (18) is used to perform deep activation of the membrane when membrane performance has significantly degraded due to long-term operation or severe fouling, and conventional cleaning can no longer fully restore its performance. The membrane regeneration process includes alternating high-concentration acid-base immersion and electric field-assisted regeneration. First, the entire membrane stack is removed from the system and immersed in a 4M (mol / L) hydrochloric acid (HCl) solution for 24 hours to thoroughly dissolve stubborn inorganic scale and hydrolyze some organic polymers. Subsequently, the membrane stack is thoroughly rinsed with a large amount of pure water until the effluent pH is close to neutral. Next, the membrane stack is immersed in a 4M (mol / L) sodium hydroxide (NaOH) solution for 24 hours to thoroughly saponify organic pollutants, expand and remove biofilm, and restore the ion exchange capacity of the anion exchange membrane. After immersion, it is thoroughly rinsed again with pure water. During this deep regeneration process, a low-intensity electric field of 0.5 V / cm (provided by a dedicated adjustable DC power supply) is applied across the membrane stack to accelerate ion migration and contaminant desorption, promoting the removal of deep fouling within the membrane pores. This results in a more thorough restoration of the membrane's ion exchange capacity, permeability, and selective permeability. After membrane regeneration, membrane resistivity and desalination rate can be restored to levels close to those of a new membrane.

[0073] Step S5: Post-processing and resource recovery.

[0074] The dilute and concentrated water effluents from the electrodialysis membrane stack module are then fed into the post-treatment and resource recovery module (5) for deep purification and resource recovery, respectively, to achieve cascade utilization of water resources and zero salt discharge. The post-treatment and resource recovery module (5) includes a freshwater deep purification unit (19) and a concentrated water concentration and crystallization unit (20).

[0075] The freshwater deep purification unit (19) receives the effluent from the electrodialysis dilution chamber, aiming to produce industrial reuse or direct discharge water that meets specific standards, or even high-purity water. The unit includes a reverse osmosis (RO) membrane module (21) and a polished ion exchange column (22). The RO membrane module (21) uses a high-desalination-rate composite polyamide membrane, prepared using interfacial polymerization technology, designed to achieve a desalination rate of over 98%, suitable for high-salinity feed water. The operating pressure of the RO membrane module is typically controlled between 4 and 6 MPa to overcome osmotic pressure and achieve efficient desalination. A security filter is installed before the RO membrane module, containing a 5-micron polypropylene wound or melt-blown filter cartridge to capture residual fine particles, preventing them from scratching or clogging the RO membrane surface and protecting the RO membrane module. The polished ion exchange column (22) receives the RO membrane permeate and further removes residual trace ions to meet the requirements for high-purity water use. The column is filled with strongly acidic cation exchange resin and strongly basic anion exchange resin, typically in a mixed bed configuration, to ensure that the resistivity of the effluent reaches above 10 MΩ·cm, and can even reach the ultrapure water standard of 18 MΩ·cm. The regeneration cycle of the ion exchange resin and the concentration of the regenerator (dilute HCl and dilute NaOH) are automatically controlled by an online resistivity meter and flow meter.

[0076] The concentrated water crystallization unit (20) receives the effluent from the electrodialysis concentrate chamber, aiming to recover and crystallize high-concentration salts, which is a key link in achieving zero liquid discharge (ZLD) of high-concentration brine in coal chemical industry. The unit includes a multi-effect evaporator (23) and a forced circulation crystallizer (24). The multi-effect evaporator (23) adopts a three-effect falling film evaporation process. Through the cascaded effector design, it uses the secondary steam of the previous effect as the heating source of the next effect, thereby significantly improving energy utilization efficiency. Its first effect operating temperature is set at 120°C. By precisely controlling the evaporation parameters, the final concentration ratio can reach 5 to 8 times, further concentrating the salts in the electrodialysis concentrate. The key contact parts of the evaporator are all made of corrosion-resistant titanium alloy (Ti-Gr2) to cope with the high salt, high temperature and potential chloride ion corrosion environment. The forced circulation crystallizer (24) receives the evaporator concentrate, maintains the slurry near the saturation temperature through an external heat exchanger, and forces the slurry to circulate through an axial flow circulation pump. Under precise conditions of supersaturation control between 1.05 and 1.10, feedback from online densitometers and conductivity meters to the control system induces salt crystallization and promotes crystal growth. The crystallizer is internally designed with a highly efficient crystal slurry separator to achieve initial separation of crystals from the mother liquor. The concentrated crystal slurry at the bottom is periodically discharged and enters a centrifugal dewatering machine for solid-liquid separation. The centrifugal dewatering machine is a horizontal screw discharge sedimentation centrifuge with a speed of up to 3000 rpm. High-speed centrifugal force separates the crystalline salt from the residual mother liquor, producing industrial-grade sodium chloride and sodium sulfate crystals with a water content of less than 5%, achieving resource recovery of high-value salt products. The separated mother liquor can be recycled to an evaporator for further concentration or undergo final treatment depending on the water quality.

[0077] Step S6: Central intelligent control.

[0078] The entire coal chemical high-concentration brine treatment process is comprehensively monitored, analyzed, diagnosed, and optimized by the central intelligent control system (6) in real time, ensuring safe, efficient, stable, and economical operation of the system. The central intelligent control system (6) consists of a rigorous hardware architecture and a powerful software architecture.

[0079] The hardware architecture is the physical foundation of the entire control system. Its core includes a Siemens S7-1500 series dual redundant programmable logic controller (25). Specifically, the main processor module CPU1518-4PN / DP is selected. This CPU has powerful processing capabilities and fast response time, and is equipped with a fail-safe module to achieve system-level redundancy and high availability, ensuring that the system can continue to operate even if a single component fails, which greatly improves the stability and reliability of operation. The PLC communicates with the distributed I / O modules, HMI workstations (26), various sensors and actuators deployed on site through the PROFINET industrial Ethernet protocol, and builds a flat and efficient automation network. The HMI workstation (26) adopts an industrial-grade touch screen PC, which has an IP65 protection rating and a wide temperature design. It is pre-installed with SCADA (Supervisory and Data Acquisition) software, which provides operators with an intuitive and real-time process flow visualization interface, graphical display of key parameters, historical data trend analysis, alarm management and remote parameter setting functions, which greatly facilitates the operation and management of the system.

[0080] The software architecture is the "intelligent core" of the central intelligent control system (6), which includes a SCADA system (27), an advanced process control (APC) layer (28), and a database management system (29). The SCADA system (27) is responsible for the real-time acquisition of all field data, monitoring of equipment status, judgment and release of alarm conditions, and interaction between operators and the process flow. It can display the flowchart of the entire electrodialysis treatment process, equipment operating status, key parameter values, and record operation logs in real time. The APC layer (28) is the key to realizing intelligent operation, and it deploys a number of advanced algorithms: adaptive control algorithm, predictive maintenance algorithm, and energy consumption optimization algorithm. The adaptive control algorithm evaluates the fluctuation of influent water quality and concentration in real time based on the data provided by the online water quality analyzer. Based on this evaluation result, the algorithm can dynamically adjust the operating parameters of the electrodialysis membrane stack, including the current density and voltage of the DC power supply and the flow rate of the dilute and concentrated chambers, to adapt to the constantly changing operating conditions, ensure that the system always operates at a high efficiency point, and maintain a stable desalination rate and product water quality. Predictive maintenance algorithms utilize historical operating data and machine learning models to accurately predict membrane fouling trends and the lifespan of equipment components, issuing early maintenance warnings. When a critical component is predicted to fail, the system automatically generates a detailed maintenance plan, such as suggesting membrane cleaning or component replacement at specific times, thereby significantly reducing unplanned downtime and ensuring continuous system operation. The energy consumption optimization algorithm comprehensively considers the DC power consumption, the power consumption of each circulating pump, the heating / cooling energy consumption, and the energy consumption of other auxiliary equipment in the electrodialysis process, establishing a multi-objective optimization model. This algorithm dynamically adjusts the operating parameters of the entire process flow to achieve the lowest comprehensive energy consumption per unit of treated water, maximizing the economic benefits of the system while ensuring the quality and volume of treated water. The database management system (29) uses enterprise-level relational databases such as SQL Server to securely and efficiently store all historical data collected by sensors, operation logs, alarm records, maintenance history data, and process parameter configurations. This database provides solid data support for data querying, trend analysis, report generation, and model training and optimization of the APC layer algorithm in the SCADA system, and is the cornerstone for realizing continuous system improvement and refined management.

[0081] Example This embodiment describes the application of the electrodialysis treatment process for high-concentration brine in coal chemical industry according to the present invention in a real industrial production environment. In a typical zero-emission coal chemical project site, the daily treatment capacity is 5000 m³ / s. 3 High-concentration brine. Typical water quality characteristics of raw high-concentration brine are: TDS 35000 mg / L, of which Na... + 10000 mg / L, Cl - 16000 mg / L, SO4 2-6000 mg / L, Ca 2+ 800 mg / L; COD 1200 mg / L; Turbidity 150 NTU; TSS 400 mg / L; pH 7.8; Water temperature 35°C.

[0082] Preprocessing module (1) running parameters and effects: Flocculation and sedimentation unit (7): Polyaluminum chloride (PAC) concentration 120 mg / L, polyacrylamide (PAM) concentration 5 mg / L. Rapid mixing zone: stirring speed 150 rpm, residence time 45 seconds. Slow mixing zone: stirring speed 20 rpm, residence time 20 minutes. Inclined tube sedimentation zone: hydraulic load 1.0 m / h, sedimentation time 3 hours. Effluent turbidity stabilized at 2.5 NTU, TSS < 10 mg / L.

[0083] Advanced oxidation unit (8): UV reactor total power 20kW, UV intensity 150mW / cm 2 The H2O2 dosage was controlled at an H2O2 to COD mass ratio of 1.5:1. The UV reactor residence time was 15 minutes. The COD removal rate of the effluent from the advanced oxidation unit was 40%, with COD reduced to 720 mg / L.

[0084] Ultrafiltration unit (9): PVDF hollow fiber membrane module, designed flux 65L / (m³) 2 • h), transmembrane pressure differential (TMP) 0.08 MPa. Automatic backwashing every 45 minutes, backwash pressure 0.15 MPa, time 45 seconds. Chemical cleaning every 48 hours, using 0.5% sodium hypochlorite and 0.2% citric acid solution successively. Ultrafiltration unit effluent turbidity 0.2 NTU, SDI value 2.8.

[0085] Operating parameters and effects of electrodialysis membrane stack module (2): Membrane stack configuration: A large electrodialysis membrane stack with 500 membrane pairs, with an effective membrane area of ​​0.8m². 2 / sheet. Both SPEEK-based CEM and QPS-based AEM membranes are modified with a PEG derivative superhydrophilic layer. The flow channel plate is made of PPS material and has a diamond-shaped protrusion structure.

[0086] Operating conditions: Diluted water inlet flow rate 200 m³ / h 3 / h, concentrate chamber inlet water flow rate 100m³ / h 3 / h. Operating current density 15mA / cm² 2 DC voltage 180V. Operating temperature 38°C. Electrode flushing fluid flow rate 0.8L / min.

[0087] Dynamic flow field management (3): CICS monitors the conductivity, differential pressure, and flow rate at the inlet and outlet of the membrane stack in real time. When the conductivity of the dilute chamber outlet water increases by 5% for 1 hour and the differential pressure in the dilute chamber increases by 0.01 MPa, the system determines that it is an initial concentration polarization. The dynamic control algorithm immediately increases the flow rate in the dilute chamber by 15% (from 0.05 m / s to 0.0575 m / s) and starts the pulse generator to run at a frequency of 0.5 Hz for 10 minutes.

[0088] Membrane cleaning and regeneration (4): Perform chemical-enhanced cleaning (acid washing + alkali washing) every 120 hours. Perform electro-flushing (reverse polarity for 3 minutes) every 24 hours. Perform ultrasonic vibration cleaning for 5 minutes every 6 hours.

[0089] Post-processing and resource recovery module (5) operating parameters and effects: Electrodialysis dilution chamber effluent: TDS 3000 mg / L, COD 50 mg / L.

[0090] Freshwater deep purification unit (19): RO membrane module operating pressure 5.0MPa, security filter 5 microns. RO permeate TDS 80mg / L, COD <5mg / L. Polished ion exchange column permeate resistivity 12MΩ·cm, meeting industrial boiler feedwater standards.

[0091] Electrodialysis concentrate effluent: TDS 70000 mg / L.

[0092] Concentrated water crystallization unit (20): The triple-effect falling film evaporator concentrates the concentrated water to a TDS of 250,000 mg / L. The forced circulation crystallizer produces NaCl and Na2SO4 crystals, which are dehydrated by a centrifugal dehydrator and have a water content of less than 4%.

[0093] Effects of the Central Intelligent Control System (6): CICS, through adaptive control, stabilized the desalination rate of the electrodialysis membrane stack at 91.5% and achieved a water recovery rate of 75%. Predictive maintenance algorithms successfully predicted bearing wear in three critical pump events and performed maintenance in advance, avoiding two unplanned downtimes. Energy optimization algorithms reduced the unit per-unit permeate power consumption (diluted permeate) by 10%, from 2.2 kWh / m³. 3 Reduced to 1.98 kWh / m 3 .

[0094] Comparative Example To highlight the beneficial effects of the present invention, this comparative example uses a traditional electrodialysis treatment process, which has significant differences in pretreatment, membrane stack structure and operation management.

[0095] Simplified pretreatment: The original high-concentration brine (water quality the same as in the example) only underwent conventional coagulation and sedimentation (PAC 150 mg / L, PAM 7 mg / L, effluent turbidity 20 NTU), and then directly passed through a multi-media filter and activated carbon filter for simple filtration, without the installation of advanced oxidation and ultrafiltration units. The SDI value is typically between 8 and 10.

[0096] Electrodialysis membrane stack: Utilizes traditional ion exchange membranes (non-composite membranes, without surface modification layers), and the flow channel plate employs a conventional mesh structure with a membrane spacing of 0.8 mm. The electrode area is not completely isolated, and the electrode flushing solution is not circulated, requiring only a single flush.

[0097] Lack of dynamic flow field management: It is only equipped with basic flow and pressure monitoring, without dynamic control algorithms and pulse generators, and the flow rate and voltage are fixed values.

[0098] The membrane cleaning system is simple: it only uses periodic chemical cleaning (acid washing and alkaline washing), without hydraulic backwashing, electric flushing and ultrasonic vibration cleaning functions.

[0099] Comparative run results: Under the same influent water quality and treatment capacity conditions as in the example, the conventional process exhibits significant disadvantages. Due to incomplete pretreatment and a high SDI value, the influent water quality to the electrodialysis membrane stack is poor.

[0100] Severe membrane fouling: After 300 hours of operation, the transmembrane pressure difference (TMP) of the electrodialysis membrane stack rose rapidly, the current efficiency decreased significantly, and the desalination rate dropped from the initial 85% to less than 70%. Severe organic adsorption and calcium sulfate scaling were observed on the membrane surface.

[0101] Frequent cleaning with poor results: Chemical cleaning is required every 72 hours, but due to stubborn contamination, the cleaning effect is unsatisfactory, and membrane performance is difficult to fully recover. Membrane cleaning is time-consuming and consumes a large amount of chemicals.

[0102] Unstable operation and short lifespan: Due to frequent membrane fouling and cleaning, the risk of mechanical damage to the membrane increases, and the membrane lifespan is significantly shortened. It usually needs to be replaced after only 6-9 months of operation.

[0103] High energy consumption: To maintain a certain desalination rate, the operating voltage needs to be increased, leading to increased DC power supply energy consumption. In addition, the increased operating resistance caused by membrane fouling further increases energy consumption.

[0104] The quality of the permeate water is substandard: the TDS of the dilute chamber effluent is usually above 5000 mg / L, making it difficult to directly enter the subsequent RO system, and the COD is usually 100-200 mg / L, causing serious pollution to the subsequent RO membrane.

[0105] Data Comparison Table The table below compares the key performance indicators of the embodiments of the present invention and the comparative examples:

[0106] As can be clearly seen from the comparative data of the above embodiments and comparative examples, the "electrodialysis treatment process for high-concentration brine in coal chemical industry" proposed in this invention achieves significant improvements in desalination efficiency, water recovery rate, operational stability, membrane lifespan, and overall energy consumption by strengthening pretreatment, optimizing membrane stack structure and membrane performance, introducing dynamic flow field management, integrating multi-mode membrane cleaning and regeneration, and performing global optimization through a central intelligent control system. The produced water quality better meets the needs of subsequent deep purification and resource utilization, effectively addressing the complex challenges of treating high-concentration brine in coal chemical industry, and demonstrating outstanding technical superiority and economic benefits.

[0107] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An electrodialysis treatment process for high-concentration brine in coal chemical industry, characterized in that, Includes the following steps: Step S1: High-concentration brine pretreatment, the high-concentration brine from coal chemical industry to be treated is input into the pretreatment module (1) for processing; Step S2: Electrodialysis membrane stack treatment, the high-concentration brine after the pretreatment module (1) is transported to the electrodialysis membrane stack module (2) for treatment by a pressurized pump; Step S3: Dynamic flow field management. During operation, the electrodialysis membrane stack module (2) is monitored and regulated in real time by the dynamic flow field management system (3). Step S4: Enhanced membrane cleaning and regeneration, the electrodialysis membrane stack module (2) is cleaned and regenerated by the enhanced membrane cleaning and regeneration system (4); Step S5: Post-treatment and resource recovery. The dilute effluent and concentrated effluent processed by the electrodialysis membrane stack module (2) are respectively sent to the post-treatment and resource recovery module (5) for deep purification and resource recovery. Step S6: Central intelligent control. The entire process is comprehensively monitored, analyzed, diagnosed and optimized by the central intelligent control system (6) in real time.

2. The electrodialysis treatment process for high-concentration brine in coal chemical industry according to claim 1, characterized in that, The pretreatment module (1) includes a flocculation and sedimentation unit (7), an advanced oxidation unit (8), and an ultrafiltration unit (9). The flocculation and sedimentation unit (7) receives the original coal chemical high-concentration brine and, based on the real-time water quality analysis results, precisely adds polyaluminum chloride and polyacrylamide composite flocculant through a metering pump; the addition process is monitored in real time by an online turbidity sensor and a pH sensor and fed back to the central intelligent control system (6), which adjusts the addition amount and addition rate according to preset logic; The advanced oxidation unit (8) receives the effluent from the flocculation and sedimentation unit (7) using a combined ultraviolet / hydrogen peroxide process. The ultrafiltration unit (9) receives the effluent from the advanced oxidation unit (8) for further removal of fine suspended solids, residual colloids, bacteria and macromolecular organic matter.

3. The electrodialysis treatment process for high-concentration brine in coal chemical industry according to claim 2, characterized in that, The flocculation and sedimentation unit (7) is provided with a rapid mixing zone, a slow mixing zone and an inclined tube sedimentation zone; The dosage concentration of the polyaluminum chloride is in the range of 50 to 200 mg / L, and the dosage concentration of the polyacrylamide composite flocculant is in the range of 2 to 10 mg / L. The rapid mixing zone achieves high-speed mixing through a mechanical stirrer with a stirring speed of 100 to 200 rpm and a residence time of 30 to 60 seconds; The slow mixing zone uses a paddle mixer with a mixing speed of 10 to 30 rpm and a residence time of 15 to 30 minutes; The inclined tube sedimentation zone uses polypropylene inclined tube packing with an angle of 60 degrees and a sedimentation time of 2 to 4 hours for efficient solid-liquid separation. The turbidity of the effluent from the flocculation and sedimentation unit (7) is less than 5 NTU.

4. The electrodialysis treatment process for high-concentration brine in coal chemical industry according to claim 2, characterized in that, The advanced oxidation unit (8) employs a combined ultraviolet / hydrogen peroxide process; The ultraviolet reactor is equipped with a low-pressure ultraviolet lamp with a wavelength of 254 nm and an ultraviolet intensity of 100 to 200 mW / cm². 2 The total power is 20kW; The hydrogen peroxide is added to the inlet of the ultraviolet reactor in the form of an industrial-grade solution with a mass concentration of 30% via a precision metering pump. The amount added is controlled within the range of a mass ratio of hydrogen peroxide to chemical oxygen demand of 1:1 to 2:

1. The ultraviolet reactor is designed with multiple baffles to ensure that the residence time of the fluid in the ultraviolet irradiation zone is uniformly distributed, and the residence time is 10 to 20 minutes. The advanced oxidation unit (8) achieves a COD removal rate of 30% to 50% in the effluent.

5. The electrodialysis treatment process for high-concentration brine in coal chemical industry according to claim 2, characterized in that, The ultrafiltration unit (9) adopts a hollow fiber membrane module, the membrane material is polyvinylidene fluoride, its molecular weight cutoff is 50 to 150 kDa, and the membrane pore size is 0.02 to 0.1 micrometers; The ultrafiltration membrane module operates under external pressure and is designed to have a flux of 50 to 80 L / (m³). 2 ·h); The ultrafiltration unit (9) is equipped with automatic backwashing and chemical cleaning functions; The automatic backwashing is performed using membrane permeate water, with a backwashing cycle of 30 to 60 minutes, a backwashing pressure of 0.1 to 0.2 MPa, and a backwashing time of 30 to 60 seconds. The chemical cleaning cycle is 24 to 72 hours, using alternating cleaning with 0.5% sodium hypochlorite solution and 0.2% citric acid solution; The ultrafiltration unit (9) produces water with a turbidity of less than 0.5 NTU and an SDI value of less than 4.

6. The electrodialysis treatment process for high-concentration brine in coal chemical industry according to claim 1, characterized in that, The electrodialysis membrane stack module (2) includes a membrane assembly (10), a flow channel structure (11), an electrode assembly (12), and a membrane stack pressurization and support structure (13). The membrane assembly (10) includes a cation exchange membrane and an anion exchange membrane. The working surfaces of the cation exchange membrane and the anion exchange membrane are both grown in situ with a superhydrophilic polyethylene glycol derivative covalently modified layer by plasma polymerization technology. The flow channel structure (11) adopts an integrally molded polyphenylene sulfide flow channel plate, and its surface is etched with periodically distributed rhomboid protrusions. The electrode assembly (12) includes an anode and a cathode. The anode is a dimensionally stable anode, and the cathode is a 316L stainless steel plate with a nickel-molybdenum alloy coating formed on its surface by electrochemical deposition. The membrane stack pressurization and support structure (13) adopts a two-end plate clamping structure. The end plates are made of fiberglass composite material with a thickness of 50 mm and are connected by 8 316L stainless steel tie rods with a diameter of 30 mm.

7. The electrodialysis treatment process for high-concentration brine in coal chemical industry according to claim 6, characterized in that, The cation exchange membrane is a sulfonated polyether ether ketone-based composite membrane with high antioxidant properties and high mechanical strength. Its fixed charge density is 1.5 to 2.0 meq / g and its thickness is 120 to 150 micrometers. The sulfonated polyether ether ketone-based composite membrane is prepared by casting a sulfonated polyether ether ketone solution onto a polyester nonwoven fabric support layer. The anion exchange membrane is a quaternized polysulfone composite membrane with high ion selectivity and high pollution resistance, with a fixed charge density of 1.2 to 1.8 meq / g and a thickness of 120 to 150 micrometers. The quaternized polysulfone composite membrane is prepared by casting it onto a polyester nonwoven fabric support layer. The polyethylene glycol derivative covalently modified layer has a thickness of 10 to 20 nanometers, which can reduce the adsorption of organic matter and sparingly soluble salts and the tendency to form scale.

8. The electrodialysis treatment process for high-concentration brine in coal chemical industry according to claim 6, characterized in that, The surface of the flow channel plate is etched with periodically distributed rhomboid protrusions. The long axis of the rhomboid protrusions forms a 45-degree angle with the main direction of the fluid. The protrusions are 0.2 mm high and 0.5 mm apart. They are used to induce micro-vortices in the narrow inter-membrane flow channel and break the fluid boundary layer. The inlet and outlet of the flow channel plate are designed with a gradual conical transition to ensure that the fluid can smoothly accelerate and decelerate when entering and leaving the membrane area; the width of the inter-membrane flow channel is 0.6 to 0.8 mm.

9. The electrodialysis treatment process for high-concentration brine in coal chemical industry according to claim 1, characterized in that, The dynamic flow field management system (3) includes a real-time monitoring unit (14), a fluid control unit (15), and a dynamic control algorithm (16). The real-time monitoring unit (14) includes a four-electrode conductivity sensor, a differential pressure sensor, and an electromagnetic flow meter installed on the inlet and outlet water pipes of the electrodialysis membrane stack (2), as well as a PT100 temperature sensor and a composite pH electrode installed at the inlet of the dilute chamber, the concentrated chamber, and the electrode chamber; the data acquisition frequency of all the sensors is 100Hz, and the data is transmitted to the central intelligent control system (6) in real time via the industrial Ethernet protocol. The fluid control unit (15) includes a variable frequency speed-regulating centrifugal pump and a proportional regulating valve; both the dilute chamber inlet pump and the concentrated chamber inlet pump are variable frequency speed-regulating centrifugal pumps, and their speed is precisely controlled by the central intelligent control system (6), with a response time of less than 0.5 seconds; each branch pipeline is equipped with a pneumatic diaphragm proportional regulating valve; the fluid control unit (15) also includes a pulse generator, which generates a fluid pulse with a frequency of 0.1 to 1 Hz and an amplitude of 10% to 20% of the instantaneous flow rate by periodically changing the local pipeline cross-section or the pump operating frequency; The dynamic control algorithm (16) runs on the central intelligent control system (6). Based on the strategy of model predictive control combined with fuzzy logic, it can adaptively adjust the pump speed, valve opening and pulse generator operating parameters according to the real-time monitored conductivity, differential pressure and temperature data.

10. The electrodialysis treatment process for high-concentration brine in coal chemical industry according to claim 1, characterized in that, The enhanced membrane cleaning and regeneration system (4) includes a multi-mode cleaning unit (17) and a membrane regeneration unit (18). The multi-mode cleaning unit (17) includes four modes: hydraulic backwash / forward wash, chemical enhanced cleaning, electro-flushing, and ultrasonic vibration cleaning. The hydraulic backwash / forward wash is achieved by reversing the flow direction of the inlet and outlet water in the dilute and concentrated chambers. The backwash flow rate is 1.5 to 2.0 times the normal operating flow rate, and the duration is 15 to 30 minutes. The chemically enhanced cleaning is carried out through a dedicated cleaning solution circulation system. The cleaning solution contains a 0.5M hydrochloric acid solution and a mixed solution of 0.1M sodium hydroxide and 0.1% sodium dodecyl sulfate. The cleaning circulation process is carried out at a temperature of 50 to 60°C, the soaking time for each cleaning step is 2 to 4 hours, and the circulation pump flow rate is 0.5 to 1.0 m / s. The electroflushing mode involves the central intelligent control system (6) periodically reversing the DC power polarity of the electrodialysis membrane stack (2), or applying a square wave pulse current with a frequency of 0.01 to 0.1 Hz. The polarity reversal time is 1 to 5 minutes, and the pulse current density is 10 to 20 A / m. 2 ; The ultrasonic vibration cleaning unit integrates multiple high-frequency ultrasonic transducers outside the electrodialysis membrane stack (2), with a working frequency of 30 to 40 kHz and a total power of 500 W. The ultrasonic vibration cleaning can be periodically turned on during the operation of electrodialysis, each lasting 5 to 10 minutes. The membrane regeneration unit (18) is used to deeply activate the membrane. The membrane regeneration process includes alternating immersion in high-concentration acid and alkali and electric field-assisted regeneration. First, the membrane stack is immersed in a 4M HCl solution for 24 hours and then rinsed. Then, it is immersed in a 4M NaOH solution for 24 hours and rinsed again. During this period, a low-intensity electric field of 0.5V / cm is applied to both ends of the membrane stack to accelerate ion migration and pollutant desorption.

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