A chlor-alkali brine deep purification device based on membrane separation and ion exchange cooperation

Abstract

The utility model discloses a kind of chlor-alkali brine depth purification device based on membrane separation and ion exchange cooperation, belong to chlor-alkali industry brine refining technical field.The device includes ultrafiltration / microfiltration membrane assembly, chelate resin exchange column, anion exchange membrane device and neutralization tank sequentially communicated along process flow.The utility model is through the three-level collaborative process of "membrane filtration pretreatment-double layer resin depth removal cation-electric drive membrane selective removal anion", realized to brine suspended solids, colloid, polyvalent cation and sulfate etc. Impurity's all-around depth purification.The utility model innovatively designs concentrated water reflux system, significantly improve water resource utilization rate, and to the waste liquid generated is handled automatically neutralization, realizes clean production.The device has the advantages of high integration, good purification effect, low operating cost, etc., can provide ultrahigh purity brine for electrolysis process, significantly improve chlor-alkali product quality and economic benefit.

Description

Technical Field

[0001] This utility model discloses a deep purification device for chlor-alkali brine based on the synergy of membrane separation and ion exchange, belonging to the field of chlor-alkali industrial brine refining technology. Background Technology

[0002] The chlor-alkali industry is the cornerstone of modern chemical industry. The efficiency and product quality of its core process—brine electrolysis—directly depend on the purity of the brine entering the tank. Traditional chlor-alkali brine refining processes typically employ a series of steps: pretreatment, chemical refining, sedimentation, filtration, and ion exchange. However, this process has gradually revealed several inherent flaws over long-term application: 1. Incomplete purification affects electrolysis efficiency and product quality. Traditional filtration units (such as sand filters and carbon filters) can only remove most suspended solids and colloids, with limited effectiveness in retaining micron- and submicron-sized fine particles and dissolved organic matter. While subsequent ion exchange resin towers can effectively remove calcium (Ca...)... 2+ ), magnesium (Mg) 2+ Polyvalent cations such as sulfate (SO4) are present, but for complex anionic impurities, especially sulfate (SO4) 2- There is a lack of economical and effective deep removal methods. These residual impurities, once they enter the electrolytic cell, will irreversibly cause scaling on the electrode surface, poisoning of the catalyst coating, increased cell voltage, increased energy consumption, and significantly reduced purity of the products chlorine (Cl2) and caustic soda (NaOH), thus shortening the service life of the electrolytic cell.

[0003] 2. The process is lengthy, equipment is scattered, and resource utilization is low. Traditional methods rely on a combination of multiple single-function equipment, resulting in a large footprint, low system integration, and complex operation and maintenance. Byproducts generated by each unit, such as filtered sludge and high-salt, high-concentration acid and alkali waste liquid from resin regeneration, are mostly discharged directly as waste. This not only wastes water resources and raw salt, but the high concentrations of inorganic salts and acidic / alkaline substances contained therein also pose a serious pollution threat to the environment, contradicting current green and sustainable industrial policies.

[0004] 3. High operating costs limit economic benefits. Frequent resin regeneration consumes large amounts of acid and alkali reagents, resulting in high chemical costs and wastewater treatment expenses. Meanwhile, issues such as decreased electrolysis efficiency due to substandard brine purity, frequent electrode replacements, and equipment maintenance downtime further increase production and operating costs, hindering the improvement of the company's economic benefits.

[0005] Therefore, there is an urgent need in this field for a new integrated technology and device that can achieve deep and comprehensive purification of brine, while also possessing resource recycling capabilities and environmentally friendly characteristics, in order to break through the bottlenecks of traditional processes and promote the transformation and upgrading of the chlor-alkali industry towards high-quality, low-energy consumption, and clean production. Utility Model Content

[0006] In view of the problems of incomplete purification, serious waste of resources, high operating costs and environmental unfriendliness of traditional chlor-alkali brine purification processes described in the background art, this utility model aims to provide a highly integrated and efficient synergistic chlor-alkali brine deep purification device.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A deep purification device for chlor-alkali brine based on the synergy of membrane separation and ion exchange is disclosed. The device includes, in sequence along the process flow, a raw brine tank, an ultrafiltration / microfiltration membrane module, a chelating resin exchange column, an anion exchange membrane device, and a neutralization tank, all connected by pipelines.

[0008] The ultrafiltration / microfiltration membrane module serves as a pretreatment unit, with its inlet pipe connected to the original brine tank. It is used to remove suspended particles, colloids, and large organic molecules from the crude brine. The module is equipped with a backwashing system, which uses a centrifugal pump, a backwash inlet pipe, and a backwash outlet pipe to periodically clean the membrane surface to maintain membrane flux.

[0009] The chelating resin exchange column is connected to the outlet end of the ultrafiltration / microfiltration membrane module and features a double-layer resin structure. The upper layer is filled with aminophosphate chelating resin, which has a high selective adsorption capacity for multivalent cations, while the lower layer is filled with macroporous strong acid cation resin, forming a two-stage deep cation purification barrier. A water distributor is installed at the bottom of the resin column to ensure that brine passes evenly through the resin layers.

[0010] The anion exchange membrane device is connected to the effluent end of the chelating resin exchange column and employs a three-chamber structure (desalinate water chamber, concentrate chamber, and polar water chamber) separated by anion exchange membranes and cation exchange membranes. The device is powered by an external DC power supply. Under the drive of an electric field, it selectively migrates and enriches anionic impurities such as sulfate ions in the desalinate water chamber to the concentrate chamber. The effluent from the concentrate chamber is returned to the inlet pipe of the ultrafiltration / microfiltration membrane module through a concentrate return pipe, forming a concentrate recycling loop; while the effluent from the desalinate water chamber is output to a high-purity brine storage tank through a finished brine pipe.

[0011] The neutralization tank is connected to the chelating resin exchange column via a regeneration waste liquid pipe, and is used to receive and treat the high-concentration acid and alkali waste liquid generated during resin regeneration. The tank is equipped with a PLC-based automatic acid and alkali neutralization agent addition system and a stirring device, which can precisely control the neutralization process based on feedback signals from an online pH meter to ensure that the waste liquid meets the standards.

[0012] Compared with the prior art, the present invention has the following significant advantages: 1. High purification precision and superior product quality: Through a three-stage synergistic purification process of "ultrafiltration / microfiltration pretreatment + deep cation removal with dual-layer resin + precise anion removal with electro-driven membrane," efficient and deep removal of various impurities is achieved. The resulting brine has extremely high purity, with sulfate ion concentration stably reduced to below 50 mg / L, laying a solid foundation for the production of high-purity chlorine (purity increase of approximately 10%) and caustic soda (purity increase of approximately 8%).

[0013] 2. Resource recycling and environmental friendliness: The innovative concentrate recirculation design returns the concentrate generated by the anion exchange membrane unit to the front end of the system for reprocessing, increasing the overall water reuse rate of the system to over 80% and significantly saving water resources. Simultaneously, the automatic neutralization treatment of high-concentration resin regeneration wastewater effectively avoids secondary pollution, meeting the requirements of green manufacturing.

[0014] 3. Low operating costs and significant economic benefits: Deep purification effectively protects the electrolytic cell and reduces cell voltage and energy consumption; the recycling of water and resources reduces raw water consumption; intelligent control and efficient process design reduce the amount of chemical reagents used by about 30% and equipment maintenance costs by about 25%, resulting in a significant improvement in overall economic benefits.

[0015] 4. High system integration and stable operation: The device adopts a modular design with tight connections between units and smooth processes. Combined with an advanced central control system, key operating parameters (such as pressure, flow rate, pH, and current density) are monitored and precisely controlled in real time, ensuring long-term stable operation and extending equipment lifespan. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a chlor-alkali brine deep purification device based on the synergy of membrane separation and ion exchange, as described in this utility model.

[0017] In the diagram: 1-Ultrafiltration / microfiltration membrane module; 101-Inlet pipe; 102-Membrane element; 103-Backwash inlet pipe; 104-Centrifugal pump; 105-Backwash drain pipe; 2-Chlorination resin exchange column; 201-Aminophosphate chelating resin; 202-Macroporous strong acid cation exchange resin; 203-Water distributor; 204-Regeneration waste liquid pipe; 205-pH online detector; 3-Anion exchange membrane device; 301-Desalinated water chamber; 302-Anion exchange membrane; 303-Electrode water chamber; 304-Cation exchange membrane; 305-Concentrate chamber; 306-Concentrate reflux pipe; 307-Finished brine pipe; 308-DC power supply; 4-Neutralization tank; 5-Raw brine tank. Detailed Implementation

[0018] The specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings. The scope of protection of this utility model is not limited to the following embodiments; those skilled in the art can make various changes or modifications within the scope defined by the claims.

[0019] Example: See Figure 1 This embodiment provides a processing capacity of 100m³. 3 A high-efficiency chlor-alkali brine purification device with a capacity of [number] hours. This device is a highly integrated physical system, with each unit connected sequentially via pipelines according to the process flow, forming a continuous purification loop.

[0020] The device includes a raw salt tank 5, an ultrafiltration / microfiltration membrane module 1, a chelating resin exchange column 2, an anion exchange membrane device 3, and a neutralization tank 4.

[0021] The original brine tank 5 is located at the beginning of the system, and its outlet pipe is directly connected to the inlet pipe 101 of the ultrafiltration / microfiltration membrane module 1 through a pipe to provide the system with the crude brine to be treated.

[0022] The purified water outlet of the ultrafiltration / microfiltration membrane module 1 is connected to the inlet at the top of the chelating resin exchange column 2 via a pipe.

[0023] The outlet at the bottom of the chelating resin exchange column 2 is connected to the inlet of the desalination chamber 301 of the anion exchange membrane device 3 via a pipe.

[0024] The outlet of the concentrate chamber 305 of the anion exchange membrane device 3 is connected to the inlet pipe 101 of the ultrafiltration / microfiltration membrane assembly 1 through the concentrate return pipe 306, thereby physically forming a concentrate circulation loop.

[0025] The regenerated waste liquid outlet at the lower sidewall of the chelating resin exchange column 2 is connected to the neutralization tank 4 via a regenerated waste liquid pipe 204. An online pH meter 205 for real-time monitoring of the waste liquid's acidity and alkalinity is installed on the regenerated waste liquid pipe 204.

[0026] The outlet of the freshwater chamber 301 of the anion exchange membrane device 3 is connected to a finished brine pipe 307, which is used to output the final high-purity brine.

[0027] in: Ultrafiltration / microfiltration membrane module 1: This module serves as the primary purification unit, with its core being a built-in polyvinylidene fluoride (PVDF) membrane element 102 with a pore size ranging from 0.1 to 0.5 μm. The module integrates a backwashing system consisting of a centrifugal pump 104, a backwash inlet pipe 103, and a backwash outlet pipe 105. The outlet of the centrifugal pump 104 is connected to the backwash inlet pipe 103, allowing for physical cleaning of the membrane element 102 without disassembling the device.

[0028] Chelating Resin Exchange Column 2: This exchange column is a vertical cylindrical container with a unique double-layer filling structure. The upper layer is tightly filled with aminophosphate chelating resin 201, specifically for deep adsorption of polyvalent cations such as calcium, magnesium, and iron; the lower layer is filled with macroporous strong acid cation resin 202 for further adsorption of residual cations. At the bottom of the resin column, a water distributor 203 is installed. This water distributor uses a combination of a porous plate and a stainless steel filter screen, and its function is to ensure that the incoming water passes evenly upward through the resin layer, ensuring a thorough and efficient ion exchange process.

[0029] Anion exchange membrane device 3: includes a membrane stack consisting of multiple anion exchange membranes 302 and cation exchange membranes 304 arranged alternately, the membrane stack being sandwiched in the middle by electrode plates at the ends, thereby forming a series of alternating parallel desalination chambers 301 and concentrate chambers 305; an electrode water chamber 303 is provided between the electrodes at both ends of the membrane stack and the adjacent ion exchange membranes; the device is externally connected to a DC power supply 308 to provide driving force for directional ion migration.

[0030] Neutralization Tank 4: This tank is a waste liquid treatment unit, equipped with a mechanical stirring device and an automatic acid-base neutralization agent addition system. The automatic addition system is connected to an online pH meter 205 on the regenerated waste liquid pipe 204 via a signal line, and can automatically start and stop according to the detected pH value to achieve online neutralization of the waste liquid.

[0031] The workflow is as follows: The crude brine from the original salt pond 5 first enters the ultrafiltration / microfiltration membrane module 1 through the inlet pipe 101. Large molecular impurities such as suspended particles and colloids are intercepted by the membrane element 102, completing the initial purification.

[0032] The pre-purified brine enters the chelating resin exchange column 2 and flows from top to bottom through the double-layer resin bed. The polyvalent cations in the brine are preferentially adsorbed by the upper layer of aminophosphate chelating resin 201, and the residual cations are further removed by the lower layer of macroporous strong acid cation exchange resin 202.

[0033] The brine purified by cation exchange enters the desalination chamber 301 of the anion exchange membrane device 3. Under the influence of the electric field established by the DC power supply 308, anion impurities such as sulfate in the brine are directed to pass through the anion exchange membrane 302 and enter the concentrate chamber 305, thereby achieving efficient separation of anions. The purified high-purity brine is output from the desalination chamber 301 through the finished brine pipe 307.

[0034] Meanwhile, the concentrated water containing anionic impurities in the concentrated water chamber 305 is returned to the inlet of the ultrafiltration / microfiltration membrane module 1 through the concentrated water return pipe 306, and re-participates in the purification process, realizing the recycling of water resources.

[0035] Once the resin in the chelating resin exchange column 2 is saturated, the resulting regeneration waste liquid is discharged into the neutralization tank 4 through the regeneration waste liquid pipe 204. The pH online detector 205 monitors the acidity and alkalinity of the waste liquid in real time and instructs the automatic addition system in the tank to add neutralizing agent. With the assistance of the stirring device, the waste liquid is completely treated to achieve harmlessness.

[0036] This invention modularly integrates ultrafiltration / microfiltration, double-layer resin ion exchange, and electrically driven membrane separation units, and innovatively incorporates an internal concentrated water circulation loop, forming a compact and functionally synergistic deep purification device. This device effectively removes various impurities from chlor-alkali brine, producing ultra-high purity brine, while significantly improving resource utilization and reducing waste emissions. It boasts advantages such as excellent purification effect, stable operation, and environmental friendliness.

Claims

1. A deep purification device for chlor-alkali brine based on the synergistic effect of membrane separation and ion exchange, characterized in that, It includes a raw salt tank (5), an ultrafiltration / microfiltration membrane module (1), a chelating resin exchange column (2), an anion exchange membrane device (3), and a neutralization tank (4) connected sequentially along the process flow. The original salt pond (5) is located at the beginning of the system, and its outlet pipe is connected to the inlet pipe (101) of the ultrafiltration / microfiltration membrane module (1). The outlet of the ultrafiltration / microfiltration membrane module (1) is connected to the inlet of the chelating resin exchange column (2) via a pipeline. The outlet of the chelating resin exchange column (2) is connected to the inlet of the fresh water chamber (301) of the anion exchange membrane device (3) via a pipeline. The outlet of the concentrate chamber (305) of the anion exchange membrane device (3) is connected to the inlet pipe (101) of the ultrafiltration / microfiltration membrane module (1) through the concentrate return pipe (306) to form a concentrate circulation loop. The regeneration waste liquid pipe (204) of the chelating resin exchange column (2) is connected to the neutralization tank (4), and the regeneration waste liquid pipe (204) is equipped with an online pH detector (205). The anion exchange membrane device (3) has a fresh water chamber (301) outlet connected to a finished brine pipe (307) for outputting high-purity brine.

2. The apparatus according to claim 1, characterized in that, The ultrafiltration / microfiltration membrane module (1) includes a membrane element (102), a backwash inlet pipe (103), a backwash outlet pipe (105), and a centrifugal pump (104). The centrifugal pump (104) is connected to the backwash inlet pipe (103) and is used to backwash the membrane element (102) at regular intervals.

3. The apparatus according to claim 1, characterized in that, The chelating resin exchange column (2) has a double-layer structure. The upper layer is filled with aminophosphate chelating resin (201), and the lower layer is filled with macroporous strong acid cation resin (202). A water distributor (203) is provided at the bottom for uniformly distributing the incoming water.

4. The apparatus according to claim 1, characterized in that, The anion exchange membrane device (3) comprises a membrane stack consisting of alternating anion exchange membranes (302) and cation exchange membranes (304), which is sandwiched in the middle by electrode plates at the ends, thereby forming a series of alternating parallel freshwater chambers (301) and concentrated water chambers (305); an electrode water chamber (303) is provided between the electrodes at both ends of the membrane stack and the adjacent ion exchange membranes.

5. The apparatus according to claim 1, characterized in that, The neutralization tank (4) is equipped with a stirring device and an automatic acid-base neutralization agent addition system. The automatic addition system is connected to the pH online detector (205) and is used to automatically adjust the agent dosage according to the pH value of the waste liquid.

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