Electrochemical in-situ chlorine and alkali production coupled concentration grading double-path closed-loop bromine extraction process method and system

Abstract

The present application belongs to the technical field of brine bromine extraction, and discloses an electrochemical in-situ chlorine production and alkali production coupled concentration grading double-path closed-loop bromine extraction process method and system. A double-chamber electrolytic cell is adopted, sodium chloride solution is introduced into the anode, and chlorine gas is produced by electro-oxidation of chlorine. Bromine is indirectly oxidized to bromine monomer by using chlorine gas, and alkali is produced synchronously at the cathode, so that the oxidizing agent and the alkali are self-sufficient and closed-loop. Two-stage bromine concentration thresholds are set, the first-stage boundary concentration C1 is 50-300 mg / L, the second-stage transfer material concentration C2 is 15-150 mg / L, and the program is forced to constrain C2 < C1. The bromine concentration of the discharged material is measured in real time, the high-bromine liquid with a bromine concentration greater than or equal to C1 is first blown out by air, and then transferred to resin adsorption after being reduced to C2; the low-bromine liquid with a concentration less than C1 is directly subjected to resin adsorption. The adsorption tail liquid is neutralized with the cathode self-produced alkali liquid, the bromine-loaded resin is eluted with the cathode alkali liquid, and the low-bromine eluate is recycled and reused. The present application integrates multiple couplings such as gradient grading, air blowing and transfer adsorption, in-situ chlorine production and alkali production, and is suitable for different grades of raw materials.

Description

Technical Field

[0001] This invention belongs to the field of brine bromine extraction technology, and relates to a closed-loop bromine extraction process and system with electrochemical in-situ chlorination and alkali production coupled with concentration-level dual-pathway extraction. It is particularly suitable for low-cost closed-loop bromine extraction from multi-grade bromine-containing raw materials such as concentrated seawater by-products of seawater desalination, bittern produced from sea salt drying, and low-concentration bromine-containing formation water from oil fields. Background Technology

[0002] Bromine, as an important basic chemical raw material, is widely used in key industrial fields such as flame retardant materials, pharmaceutical intermediates, water treatment agents, and new energy materials. Bromine resources are mainly found in bromine-containing systems such as seawater, bittern from sea salt production, concentrated seawater from seawater desalination byproducts, underground brine, and produced water from oil fields. Developing efficient, low-cost bromine extraction technologies adaptable to raw materials of different grades is of great significance for promoting the multi-level utilization of seawater / brine resources. This paper will compare and analyze the technical shortcomings of existing mainstream technologies and publicly disclosed core patented technologies one by one: 1. Mainstream traditional air-blowing bromine extraction process The traditional air-blowing bromine extraction process involves: acidification of bromine-containing brine → oxidization of bromide ions with liquid chlorine to generate elemental bromine → blowing bromine vapor into the air → absorption and enrichment by sulfur dioxide → secondary oxidation and distillation to obtain industrial bromine. After bromine blowing, the acidic brine is neutralized and discharged into the sea. This process has been industrially validated for decades and is technically mature, but it still has several key shortcomings: First, the consumption of exogenous reagents is enormous, and the production cost is rigid: oxidants and neutralizers are all purchased from outside sources, liquid chlorine is a highly toxic and hazardous chemical, and the investment in supporting storage tanks, filling, transportation, and safety explosion-proof facilities is huge, and the costs of daily safety management and environmental filing remain high; the purchase of large quantities of caustic soda continues to increase the rigid production cost per ton of bromine.

[0003] Secondly, the single air-blowing process for low-grade raw materials is energy-intensive: natural seawater and desalinated concentrated seawater have low bromide ion concentrations, and the partial pressure of elemental bromine in the liquid phase after oxidation is extremely low. To ensure the bromine blowing rate, a high-power centrifugal fan is required to continuously supply a large amount of hot air, resulting in a comprehensive power consumption per ton of bromine that is far higher than that of bittern raw materials. If only air blowing is used, energy consumption is the core bottleneck limiting the utilization of low-grade bromine resources. In addition, the existing air blowing process lacks a mid-stream diversion mechanism. As the bromine concentration in the tower continues to decrease, the fan operates at a high load continuously, resulting in extremely high energy consumption. Furthermore, a large amount of low-bromine residual liquid is directly neutralized and discharged, leading to serious loss of bromine resources.

[0004] 2. Existing single resin adsorption process To address the high energy consumption issue in blowing out low-grade brine, existing technologies employ bromine-selective resins to enrich the bromine components in dilute brine. However, this approach has significant drawbacks: First, resin elution requires continuous consumption of purchased caustic soda or other elution reagents. While this reduces fan energy consumption, the cost advantage of these reagents is minimal. Second, existing processes rely solely on resin adsorption. For high-grade raw materials, the resin adsorption load is extremely high, leading to a significant increase in resin regeneration frequency. The consumption of elution and regeneration reagents, along with resin wear and tear, offsets the energy-saving benefits of enrichment. Consequently, existing resin processes are only suitable for low-grade brine and cannot accommodate raw materials of varying concentrations and grades. Third, the eluent often employs an acidification and secondary blowing process, requiring the addition of an acid hydrolysis reactor and a secondary blowing tower. This further increases equipment investment and sulfuric acid consumption, raising production costs.

[0005] 3. Existing electrochemical bromine extraction proximity technology Current electrochemical bromine extraction methods are divided into two categories: direct electro-oxidation of bromine and indirect oxidation via electrolytic chlorination. (1) Direct electro-oxidation process of bromide ions: Chinese patent CN1771353A uses a cation exchange membrane flow cell to electrochemically oxidize bromide at a current density of 4~7 mA / cm 2 Under certain conditions, bromide ions are directly oxidized to elemental bromine at the anode. Chinese patent CN114956264A discloses a method for separating bromine from liquid using electrochemistry, which achieves bromine separation by configuring an anode material capable of directly electro-oxidizing bromide ions. Chinese patent CN119824432A proposes to extract bromine from brine containing high concentrations of chloride ions and low concentrations of bromide ions through electro-oxidation, reducing chloride interference by selecting an appropriate oxidation potential. However, the chloride ion concentration in the brine is much higher than that of bromide ions. During the direct electro-oxidation of bromide ions at the anode, a large number of chlorine and oxygen evolution side reactions occur, resulting in a significant increase in electricity consumption per ton of bromine. The alkaline solution produced at the cathode is directly discharged with the tail liquid without cross-process reuse. Neutralization and resin elution still require the purchase of caustic soda, making a closed-loop reagent system impossible.

[0006] (2) Electrolytic chlorine production and indirect oxidation bromine extraction process: US Patent US9963362 discloses a method for electrochemical removal of bromides and / or chlorides, in which bromides can be directly oxidized to bromine by electrochemical anode or indirectly oxidized to bromine by electrochemically generated oxidant (such as chlorine gas); Chinese patents CN115074754A and CN118756152A establish a segmented bromine recovery system, which combines the bromine formed by electrolytic oxidation with the bromine replacement by chlorine gas obtained from electrolysis, thereby reducing recovery costs. However, the above-mentioned existing solutions still have several shortcomings: First, the sodium hydroxide produced at the cathode is only used in small quantities for tail liquid neutralization and has not been extended to the resin alkali elution process; Second, it is only equipped with a single air blowing unit, and there is no resin adsorption diversion path for low-grade brine, resulting in high energy consumption of low-grade raw materials; Third, there is no gradient monitoring and transfer adsorption mechanism in the blowing tower, and the low-bromine waste liquid at the end of the blowing is directly discharged, resulting in large bromine loss.

[0007] For split-path bromine extraction, a small number of documents only describe the separate construction of two independent production lines, where the electrolysis, reagent and automatic control equipment of the two systems are completely separated, making it impossible to share one set of chlorine and alkali production units via electrolysis, and thus no synergistic cost reduction effect can be achieved. In summary, there has been no public disclosure in the industry of an integrated closed-loop bromine extraction system that simultaneously integrates in-situ self-sufficient chlorine and alkali production via electrolysis, intelligent classification and dual-path coupling of two-stage bromine concentration, internal neutralization of high-concentration alkaline eluate from resin and acidic absorption liquid, segmented resin elution, and cyclic reuse of low-concentration bromine eluate, which cannot simultaneously address multiple pain points of hazardous chemicals, energy consumption and reagent loss. Contents of the Invention

[0008] In view of the defects of existing bromine extraction processes, the present invention provides an electrochemical in-situ chlorine and alkali production coupled concentration classification dual-path closed-loop bromine extraction process method and system, which realizes full internal self-sufficiency of oxidant, elution alkali and neutralization alkali, realizes the synergistic coupling of air blowing and resin adsorption through intelligent shunting at two bromine concentration thresholds, constructs a full closed-loop system for multiple resources of bromine and alkali, greatly reduces energy consumption and reagent cost, improves the comprehensive recovery rate of bromine, and is suitable for industrial continuous production of bromine-containing raw materials in the full concentration range.

[0009] The technical solution of the present invention is as follows: In one aspect, the present invention provides an electrochemical in-situ chlorine and alkali production coupled concentration classification dual-path closed-loop bromine extraction process method, comprising the following steps: (1) Raw material pretreatment and acidification: after the bromine-containing raw material is filtered to remove suspended impurities, it is subjected to synergistic online acidification with steam distillation tail liquid and sulfuric acid, and then sent to the oxidation tower; (2) In-situ chlorine and alkali production by membrane electrolysis: the prepared sodium chloride brine is fed to the anode of a membrane-separated two-chamber electrolytic cell, and the prepared sodium chloride or / and sodium hydroxide solution is fed to the cathode of the two-chamber electrolytic cell for electrolysis; (3) First-stage bromine oxidation: the chlorine gas produced in the anode chamber of the electrolytic cell is sent to the oxidation tower, where it fully contacts the acidified bromine-containing raw material in countercurrent, and bromide ions in the raw material are oxidized to bromine by the chlorine gas; (4) Online detection of bromine concentration and automatic shunting of gradient classification dual-path: a first-stage online bromine concentration detection device is arranged on the discharge pipeline of the oxidation tower, which supports online setting of the first-stage critical concentration C1; a second-stage online bromine concentration detection device is arranged inside the liquid phase of the air blowing tower, which supports online setting of the second-stage transfer concentration C2, and the system program forcibly restricts C2<C1; the system is provided with two paths of air blowing and resin adsorption, and automatic shunting is performed according to the comparison result between the detected concentration and the set critical concentration; (5) Chemical absorption: the bromine vapor blown out from the air blowing tower in step (4) is mixed with sulfur dioxide flue gas and then sent to the absorption tower for reverse reaction, so as to obtain an acidic high-concentration bromine absorption finished liquid, which is stored in an absorption finished liquid tank; (6) Stepwise elution of resin with lye self-produced at cathode: The bromine-loaded resin after adsorption is pre-eluted with the buffered and circulated low-concentration bromine eluent to remove the bromine components on the surface layer of the resin, and then the fresh lye from the self-produced lye storage tank is introduced for deep elution; (7) Two-stage bromine oxidation and steam distillation: The pH of the finished absorption solution is monitored in real time, and sulfuric acid is added for acidification when pH>3.5; the acidified high-concentration bromine-containing solution is sent to the distillation tower, mixed with the chlorine gas produced at the anode of the electrolytic cell, bromide ions in the system are oxidized to bromine simple substance, and industrial bromine products are obtained through steam distillation and rectification purification.

[0010] Preferably, the automatic shunting logic of step (4) is as follows: ① When the bromine concentration at the outlet of the oxidation tower is ≥C1, the stream is automatically diverted to the air blowing path for main blowing to obtain bromine vapor; the liquid-phase bromine concentration in the air blowing tower is monitored in real time, and the material is automatically transferred to the resin adsorption path when the bromine concentration in the tower drops to C2; the acidic tail liquid discharged after bromine adsorption in step (4) is neutralized with the lye from the self-produced lye storage tank to reach the standard and then discharged; C1 is 50~300 mg / L; C2 is 15~150 mg / L; ② When the bromine concentration at the outlet of the oxidation tower is <C1, the stream is automatically diverted to the resin adsorption path to capture the liquid-phase bromine.

[0011] Preferably, in step (2), the mass fraction of sodium chloride brine at the anode of the two-chamber electrolytic cell is 5%~28%, preferably 18%~26%; the mass fraction of the sodium chloride and / or sodium hydroxide solution at the cathode of the two-chamber electrolytic cell is 0.1%~5%. The anode adopts a chlorine evolution selective electrode, which electrochemically oxidizes chloride ions to generate chlorine gas; the cathode synchronously produces sodium hydroxide lye which is collected into the self-produced lye storage tank.

[0012] Preferably, in step (2), the membrane is a diaphragm or ion exchange membrane for caustic soda production; during electrolysis, the anode working potential is controlled at 1.25~1.45 V vs SHE, and the current density is 20~100 A / dm 2 .

[0013] Preferably, in step (2), the cathode produces sodium hydroxide lye with a mass fraction of 1%~10%, and the self-produced lye storage tank is provided with two independent distribution pipelines, which are respectively used for the neutralization process of resin adsorption tail liquid and the stepwise elution process of bromine-loaded resin.

[0014] Preferably, in step (1), the on-line acidification pH is 3.0~4.0, preferably 3.5.

[0015] Preferably, in step (6), the resin adsorption space velocity is 1~5 BV / h; the elution operation parameters are: the mass fraction of the lye self-produced by the cathode is 1%~10%, preferably 3%~5%; the elution space velocity is 0.5~1.5 BV / h, and the elution temperature is controlled from room temperature to 60°C. The alkaline high-concentration bromine eluate generated in step (6) is sent to the absorption finished liquid tank to be mixed with the acidic absorption finished liquid; the low-concentration bromine eluate is transported to the buffer tank for storage, and is recycled as the resin pre-elution medium for the next round.

[0016] Preferably, the bromine-containing raw material includes any one or a mixture of more of seawater, concentrated seawater as a desalination by-product, sea salt bittern, low-concentration bromine-containing chemical wastewater, underground brine, and bromine-containing oilfield formation water.

[0017] In another aspect, the present invention provides a system for implementing the above-mentioned electrochemical in-situ chlorine and alkali production coupled concentration classification two-path closed-loop bromine extraction process method, comprising: A raw material buffer tank, wherein the input end of the raw material buffer tank is connected to a bromine-containing raw material delivery pipeline, and the discharge pipeline of the raw material buffer tank is provided with an on-line sulfuric acid mixing pipeline; A membrane electrolysis unit, comprising an anode chamber and a cathode chamber of a two-chamber electrolyzer separated by a caustic soda production diaphragm or an ion exchange membrane, equipped with a supporting anolyte preparation tank and a catholyte preparation tank; the output end of the anolyte preparation tank is communicated with the feed pipeline of the anode chamber, the output end of the catholyte preparation tank is communicated with the feed pipeline of the cathode chamber, a selective chlorine evolution electrode is assembled in the anode chamber, the gas-phase output pipeline for chlorine gas in the anode chamber is divided into two paths, which are respectively communicated with the gas-phase feed inlets of the oxidation tower and the distillation tower; the lye discharge pipeline of the cathode chamber is communicated with the feed inlet of the cathode self-produced lye storage tank; The cathode self-produced lye storage tank is provided with two independent lye distribution pipelines, which are respectively communicated with the tail liquid neutralization section and the lye staged elution section of the resin adsorption unit; An oxidation tower, wherein a first-stage on-line bromine concentration detection diverter valve group is assembled on the liquid-phase discharge pipeline of the oxidation tower, and a first-stage boundary concentration C1 configuration module is built in the valve group; the valve group is provided with two discharge branches, which are respectively communicated with the feed end of the air blowing-out unit and the feed end of the resin adsorption unit; An air blowing-out unit, which is equipped with a second-stage on-line bromine concentration monitoring component, with a built-in second-stage material transfer concentration C2 configuration module, and the system program forcibly locks C2<C1; the air blowing-out unit is provided with a low-bromine residual liquid outlet and a bromine vapor gas-phase outlet; the low-bromine residual liquid outlet is communicated with the feed port of the resin adsorption unit through a material transfer pipeline; the bromine vapor gas-phase outlet is communicated with the gas inlet pipeline of the absorption tower; An absorption tower and an absorption finished liquid tank, wherein the absorption tower is equipped with a supporting sulfur dioxide gas inlet pipeline, and the liquid-phase discharge of the absorption tower is connected to the absorption finished liquid tank; the absorption finished liquid tank is equipped with a supporting sulfuric acid dosing pipeline, and the discharge pipeline of the absorption finished liquid tank is communicated with the feed port of the distillation tower; Distillation column, the distillation column is connected to the anode chlorine gas delivery pipeline of the membrane electrolysis unit and the steam supply pipeline; the top of the distillation column is provided with a bromine finished product discharge port, and the distillation tail liquid discharged from the bottom of the distillation column flows back to the acidification pipeline at the front end of the raw material cache for recycling; Resin adsorption unit, which is respectively provided with a low-bromine residual liquid feed port, a two-stage alkaline desorption section, a low-concentration bromine eluent buffer tank, a high-concentration bromine eluent outlet, and an acidic tail liquid discharge port; the high-concentration bromine eluent pipeline is connected to the absorption completed liquid pool; the low-concentration bromine eluent outlet is communicated with the buffer tank, and the discharge pipeline of the buffer tank flows back to the front end of resin desorption to be used as the pre-desorption medium for the next round; the acidic tail liquid pipeline is connected to the neutralization branch of the cathode self-produced lye storage tank, and the waste liquid after neutralization is discharged up to the standard; Parameter configuration module, including a threshold logic judgment unit and an execution signal output unit.

[0018] Preferably, the parameter configuration module can independently adjust the first-stage cut-off concentration C1 and the second-stage transfer concentration C2 online, the program forcibly locks C2<C1, and the C2 judgment logic is only effective for the transfer action of the low-bromine residual liquid discharged from the air blowing unit.

[0019] The overall innovative concept of the present invention and the analysis of three core collaborative innovations are as follows: The core innovation point of the present invention is a parameterizable and configurable two-stage bromine concentration gradient classification dual-path integrated closed-loop coupling process architecture, which can flexibly adjust the two-stage concentration control parameters according to the bromine grade of the raw material, and rely on three innovations to cooperate to achieve multiple technical effects, the three are inseparable and mutually supportive: The first collaborative innovation: full-membrane electrolysis synchronously produces chlorine and lye in situ, the whole process realizes closed-loop self-sufficiency of reagents, and reduces the cost of hazardous chemicals and externally purchased reagents. A diaphragm or ion-exchange membrane for caustic soda production is used to divide the two-chamber electrolytic cell, the anode selective chlorine evolution electrode stably produces chlorine gas, which is supplied to the first-stage oxidation tower and the second-stage distillation column in two paths, completely replacing externally purchased liquid chlorine, eliminating liquid chlorine storage tanks, hazardous chemical transportation, and safety explosion-proof supporting facilities, greatly reducing safety control and infrastructure investment; the cathode stably produces 1%~10% self-produced caustic soda, and two independent distribution pipelines are set up, which are simultaneously used for two lye-consuming processes: neutralization of acidic tail liquid from resin adsorption and segmented desorption of bromine-loaded resin, no need to purchase commercial caustic soda.

[0020] Second collaborative innovation: A two-stage independently adjustable concentration gradient dual-path intelligent coupling separation architecture, with a single device compatible with all grades of bromine-containing raw materials, significantly reducing comprehensive energy consumption. Two stages of independent parametric concentration thresholds are set (C1: 50~300 mg / L, C2: 15~150 mg / L, the program enforces C2<C1), forming a gradient collaboration logic of "main air blowing for high-concentration raw materials, transferring low-bromine residual liquid at the end of bromine blowing to resin, and direct resin adsorption for low-concentration raw materials". The two separation units share the same set of electrolysis system for chlorine and alkali production, eliminating the need for two independent sets of chemical and automatic control systems. The two-stage gradient transfer and adsorption mechanism is a core improvement not disclosed in the prior art, which can recover low-concentration bromine that is difficult to strip in the blowing tower, realize integrated continuous treatment of multiple raw materials such as bittern and desalinated concentrated seawater, and achieve full coverage of raw material applicability.

[0021] Third collaborative innovation: A closed-loop system of segmented resin elution and internal cyclic reuse of low-concentration bromine eluent, eliminating the acidolysis kettle and complete set of secondary bromine blowing equipment in traditional processes. The resin regeneration adopts a two-stage process of "pre-elution with recycled low-concentration bromine eluent + deep elution with fresh electrolytic alkali"; the high-concentration bromine eluent produced by pre-elution is sent to the absorption finished liquid tank to reduce distillation steam consumption; the low-concentration bromine eluent produced by deep elution is sent to the buffer tank for storage, and is recycled as the medium for the next round of resin pre-elution, making full use of the residual free alkali in the eluent, and significantly reducing the consumption of fresh electrolytic alkali.

[0022] The advantages and positive effects of the present invention are: (1) Eliminating outsourced hazardous chemicals, significantly reducing the comprehensive cost of chemicals. Relying on in-situ chlorine and alkali production by membrane electrolysis and full-process reuse, the chemical cost per ton of bromine is reduced, and the environmental protection and safety management pressure brought by the high-risk medium of liquid chlorine is eliminated.

[0023] (2) Two-stage gradient dual-path collaboration, adapting to all grades of raw materials, with comprehensive energy consumption significantly reduced. A single device can process raw materials of different grades at the same time, two separation paths share the electrolysis system, and the high energy consumption defect of low-bromine air blowing is avoided.

[0024] (3) Dual bromine closed-loop recovery mechanism, improving the comprehensive recovery rate of bromine. The low-bromine residual liquid at the end of air blowing is transferred to resin for deep capture, and the low-concentration bromine eluent is recycled for reuse. The synergistic effect of the dual closed loops improves the bromine recovery rate.

[0025] (4) Internal self-balancing of acid and alkali, simplifying the process flow and reducing equipment investment. The high-concentration alkaline bromine eluent is directly sent to the absorption finished liquid tank, eliminating the complete set of acidolysis and secondary bromine blowing equipment in traditional processes, and reducing equipment investment and labor costs.

[0026] (5) Intelligent control of automated two-stage thresholds, with strong resistance to raw material fluctuations. The system parameters C1 and C2 can be flexibly configured and adjusted online, which can match the optimal shunting parameters in real time according to incoming materials, and promote the large-scale utilization of bromine resources of different grades. Brief Description of the Drawings

[0027] Figure 1 is the process flow diagram of the electrochemical in-situ chlorine and alkali production coupled concentration classification dual-path closed-loop bromine extraction process in Example 1.

[0028] Figure 2 is the process flow diagram of the traditional single resin adsorption bromine extraction process in Comparative Example 1.

[0029] Figure 3 is the process flow diagram of the traditional single air blowing-out bromine extraction process in Comparative Example 2. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below with reference to the accompanying drawings and specific examples. The following examples are only descriptive, not restrictive, and shall not be used to limit the protection scope of the present invention.

[0031] Example 1: High-concentration raw material of sea salt bittern (air blowing-out + gradient operation of resin with low-bromine residual liquid in the tower) The bromine-containing raw material is sea salt bittern, with an initial bromide ion concentration of 3000~3500 mg / L, which is a high-grade raw material. The configuration sets the first-stage cut-off concentration C1=100 mg / L, and the second-stage transfer concentration C2=50 mg / L (satisfying C2<C1). The process flow of the electrochemical in-situ chlorine and alkali production coupled concentration classification dual-path closed-loop bromine extraction method is as follows Figure 1 shown, the specific operations include the following steps: (1) Raw material pretreatment and acidification: After the raw material is filtered to remove suspended salt sludge impurities, the distillation reflux tail liquid is used in combination with externally purchased sulfuric acid for online acidification, the pH is stably controlled at ≈3.5, and the acidified raw material is sent to the oxidation tower.

[0032] (2) In-situ chlorine and alkali production by membrane electrolysis: A salt solution with a mass fraction of 20% prepared from sodium chloride is stored in the anolyte preparation tank and delivered to the anode chamber of the two-chamber electrolyzer; a 1% by mass sodium chloride aqueous solution is prepared in the catholyte preparation tank and sent to the cathode chamber; the electrolyzer uses a perfluorosulfonic acid-perfluorocarboxylic acid composite cation exchange membrane for caustic soda production to separate the anode and cathode chambers, and the anode is equipped with a ruthenium-iridium based selective chlorine evolution electrode; the constant potential is controlled at 1.35 V vs SHE for the anode, with a current density of 20 A / dm 2 , the anode oxidizes chloride ions to continuously produce chlorine gas, and the cathode synchronously precipitates hydrogen gas and generates a sodium hydroxide lye with a mass fraction of 5%, and the self-produced lye is uniformly stored in the cathode self-produced lye storage tank; the mass fraction of the lye meets the preferred range of 3%~5%, and can be directly used for segmented elution of resin and tail liquid neutralization.

[0033] (3) First-stage bromine oxidation: One path of the wet chlorine gas produced by the electrolysis anode is introduced into the oxidation tower, and fully contacts the acidified bromine-containing raw material in countercurrent (chlorine excess coefficient 115%), so that the bromide ions in the raw material are completely oxidized to elemental bromine.

[0034] (4) Online detection of bromine concentration and primary diversion: The discharge pipeline of the oxidation tower is equipped with a primary online bromine concentration detection device to measure the bromine concentration in the liquid phase in real time; the bromine concentration of this batch of oxidation discharge is 3420 mg / L, which is higher than the C1=100 mg / L threshold. The system automatically switches to the air blowing path, and the liquid is sent into the air blowing tower. The secondary C2 monitoring module in the tower is started simultaneously.

[0035] (5) Air blowing and sulfur dioxide chemical absorption: At room temperature, air is blown out of the tower in a countercurrent manner. The bromine-containing tail gas is sent into the absorption tower to react in the reverse direction with the sulfur dioxide flue gas to generate acidic high-concentration bromine absorption liquid, which is stored in the absorption liquid pool. The bromine concentration in the liquid phase in the tower is monitored in real time. When it drops to C2=50 mg / L, the transfer pump is automatically turned on, and the low bromine residual liquid is transported to the resin adsorption unit for deep bromine capture.

[0036] (6) Two-stage elution: The low-bromine residue discharged from the air blowout tower enters the packing SP207 brominated modified macroporous resin (Mitsubishi Chemical SEPABEADS). TM The adsorption unit has an adsorption space velocity of 3 BV / h. After adsorption, the acidic tail liquid is neutralized with alkali from the self-produced alkali storage tank before being discharged. After adsorption, under the condition of elution space velocity of 0.5 BV / h, the surface bromine is pre-eluted with circulating low-concentration bromine eluent from the buffer tank to produce high-concentration bromine (≥3 g / L) eluent, which is then sent to the absorption completion liquid pool. Then, 5% fresh sodium hydroxide solution is introduced for deep elution at room temperature to produce new low-concentration bromine (<3 g / L) eluent, which is then sent to the buffer tank for buffering and recycling for the next round of pre-elution.

[0037] (7) Two-stage bromine oxidation and steam distillation: The pH of the absorption completion liquid pool is monitored in real time. Under this condition, the pH is <3.5, so sulfuric acid is not added for acidification. The high bromine liquid in the absorption completion liquid pool is sent to the distillation tower. Another path of electrolytic chlorine gas is introduced into the distillation tower for secondary oxidation of bromide ions (chlorine excess coefficient 115%). Saturated steam is introduced to heat the distillation. The bromine produced at the top of the tower is purified to obtain the finished bromine product. The distillation tail liquid at the bottom of the distillation tower is returned to the raw material acidification pipeline for recycling.

[0038] The system operated stably for 48 hours continuously, with multiple bromine samples taken and analyzed every 4 hours. Bromine ions were detected using spectrophotometry. Operational results: This system eliminates the problem of bromine loss with waste liquid at the end of the traditional air-blowing method. The overall bromine recovery rate is approximately 92%, which is about 12 percentage points higher than the traditional bitterning single-air-blowing process (recovery rate approximately 80%). Furthermore, the system completely eliminates the need for purchased liquid chlorine and commercial caustic soda. The low-bromine residue in the tower is transferred to resin adsorption after the concentration drops to C2, reducing ineffective aeration energy consumption by the blower and lowering the overall cost of reagents and energy by approximately 25%.

[0039] Example 2: Bromine-bearing formation water in oilfields with fluctuating bromine concentration (wide-range feedstock, differentiated parameter configuration) The bromine-containing raw material uses oilfield bromine-containing formation water with a bromine concentration fluctuation range of 40~220 mg / L. The configuration sets the first-stage critical concentration C1=150 mg / L and the second-stage transfer concentration C2=60 mg / L (satisfying C2<C1). The specific operations are as follows: (1) Raw material pretreatment and acidification: The only difference from step (1) of Example 1 is that the bromine-containing raw material is acidified to pH≈3.0.

[0040] (2) In-situ chlorine and alkali production by membrane electrolysis: The only difference from step (2) of Example 1 is that the anode is filled with 18% sodium chloride brine, the cathode is filled with 0.5% sodium chloride brine; the current density is 30 A / dm 2 ; the cathode produces 4.5% sodium hydroxide lye.

[0041] (3) First-stage bromine oxidation: Same as step (3) of Example 1.

[0042] (4) Online bromine concentration detection and graded split flow: When the bromine in the oxidized effluent is ≥150 mg / L, it automatically goes to the air blowing path; when the bromine is <150 mg / L, it directly enters resin adsorption; when the bromine in the air blowing tower drops to 60 mg / L, it automatically transfers to resin adsorption.

[0043] (5) Air blowing and sulfur dioxide chemical absorption: Same as step (5) of Example 1.

[0044] (6) Two-stage segmented elution: The only difference from step (6) of Example 1 is that the resin adsorption space velocity is 2 BV / h; segmented elution is performed with 4.5% NaOH at 35°C, and the elution space velocity is 1.0 BV / h.

[0045] (7) Second-stage bromine oxidation and steam distillation: Same as step (7) of Example 1.

[0046] The detection conditions are the same as those in Example 1. Operation effects: The whole system shares one set of electrolytic chlorine and alkali production unit, no need for two sets of chemical agent systems; the high-concentration eluate increases the bromine content of the finished absorption liquid, reduces the steam distillation load, and the comprehensive bromine recovery rate is about 91%; compared with the traditional full air blowing process, the power consumption of the fan is reduced by 12%.

[0047] Example 3: Concentrated brine by-produced from seawater desalination (low-concentration raw material, direct resin path as the main process) The bromine-containing raw material is concentrated brine by-produced from seawater desalination, with a bromide ion concentration of 80~120 mg / L, which is a low-grade raw material. The configuration sets the first-stage critical concentration C1=90 mg / L and the second-stage transfer concentration C2=35 mg / L (satisfying C2<C1). The specific operations are as follows: (1) Raw material pretreatment and acidification: Same as step (1) of Example 2.

[0048] (2) In-situ chlorine and alkali production by membrane electrolysis: The only difference from step (2) of Example 1 is that the cathode is equipped with 1% dilute sodium hydroxide solution; the anode potential is 1.40 V vs SHE, and the current density is 40 A / dm 2 ; 3.5% sodium hydroxide lye is produced at the cathode.

[0049] (3) First-stage bromine oxidation: Same as step (3) of Example 1.

[0050] (4) Online bromine concentration detection and classified split flow: Oxidation discharge with bromine ≥90 mg / L enters the air blow-out tower, and oxidation discharge with bromine <90 mg / L directly enters resin adsorption; when the bromine in the air blow-out tower drops to 35 mg / L, it automatically switches to resin adsorption.

[0051] (5) Air blow-out and sulfur dioxide chemical absorption: Same as step (5) of Example 1.

[0052] (6) Two-stage segmented elution: The only difference from step (6) of Example 1 is that the resin adsorption space velocity is 4 BV / h, and segmented elution is performed at room temperature with 3.5% sodium hydroxide.

[0053] (7) Second-stage bromine oxidation and steam distillation: Same as step (7) of Example 1.

[0054] The detection conditions are the same as those in Example 1. Operation effect: The comprehensive bromine recovery rate is about 90%, which is about 10 percentage points higher than that of the traditional single air blow-out process; compared with the traditional single resin adsorption process (which requires purchased liquid chlorine for oxidation and purchased caustic soda for elution), the chemical cost is reduced by about 75%; only the high-bromine section is subjected to air blow-out, and the power consumption of the fan is reduced by about 32% compared with full air blow-out.

[0055] Example 4: Boundary extreme value verification of C1 and C2 (C1=50 mg / L, C2=15 mg / L) To verify the feasibility of the lower limit of the primary demarcation concentration C1 value interval (50 mg / L) and the lower limit of the secondary transfer concentration C2 value interval (15 mg / L), the bromine-containing formation water from the oil field with large bromine concentration fluctuation in Example 2 was used for verification. The configuration is set to C1=50 mg / L and C2=15 mg / L (satisfying C2<C1). The specific operations are as follows: (1) Raw material pretreatment and acidification: Same as step (1) of Example 2.

[0056] (2) In-situ chlorine and alkali production by membrane electrolysis: The only difference from step (2) of Example 1 is that the anode is equipped with 18% sodium chloride brine, and the cathode is equipped with 0.5% sodium chloride solution; the electrolytic cell uses an asbestos-free perfluorinated composite diaphragm to separate the anode chamber and the cathode chamber; the anode potential is 1.30 V vs SHE, and the current density is 30 A / dm 2 ; 4% sodium hydroxide lye is produced at the cathode.

[0057] (3) First-stage bromine oxidation: Same as step (3) in Example 1.

[0058] (4) Online bromine concentration detection and classified split flow: When the bromine in the oxidized effluent is ≥50 mg / L, it automatically goes to the air blowing path; when the bromine is <50 mg / L, it directly enters the resin adsorption process. When the bromine in the air blowing tower drops to 15 mg / L, it automatically switches to resin adsorption.

[0059] (5) Air blowing and sulfur dioxide chemical absorption: Same as step (5) in Example 1.

[0060] (6) Two-stage segmented elution: The only difference from step (6) in Example 1 is that the resin adsorption space velocity is 5 BV / h; elution is performed at room temperature with 4% sodium hydroxide, and the elution space velocity is 1.5 BV / h.

[0061] (7) Second-stage bromine oxidation and steam distillation: Same as step (7) in Example 1.

[0062] The detection conditions are the same as those in Example 1. Operation effect: Under this configuration, more than about 85% of the feed liquid enters the air blowing tower, the operating load of the fan is relatively higher than that in Example 2, and the comprehensive bromine recovery rate is about 92%. When the bromine concentration of the low-bromine residual liquid in the air blowing tower drops to 15 mg / L, there is still an operable liquid-phase mass transfer driving force, which verifies the engineering feasibility of the lower limit values of C1=50 mg / L and C2=15 mg / L. Due to the high operating load of the fan, it is recommended in practical engineering to comprehensively optimize the value of C1 according to the power cost and the price of bromine products.

[0063] Example 5: Verification of boundary extreme values of C1 and C2 (C1=300 mg / L, C2=150 mg / L) In order to verify the feasibility of the upper limit of the value range of the first-stage cutoff concentration C1 (300 mg / L) and the upper limit of the value range of the second-stage transfer concentration C2 (150 mg / L), the high-concentration sea salt bittern in Example 1 was used as the raw material for verification. The configuration is set to C1=300 mg / L and C2=150 mg / L (satisfying C2<C1). The specific operations are as follows: (1) Raw material pretreatment and acidification: Same as step (1) in Example 1.

[0064] (2) In-situ chlorine and alkali production by membrane electrolysis: The only difference from step (2) in Example 1 is that the electrolytic cell uses an asbestos-free perfluorinated composite diaphragm for caustic soda production to separate the anode chamber and the cathode chamber; the anode potential is 1.40 V vs SHE, and the current density is 25 A / dm 2 .

[0065] (3) First-stage bromine oxidation: Same as step (3) in Example 1.

[0066] (4) Online detection and classification of bromine concentration: All bromine in the oxidized output is above 300 mg / L and enters the air blowing tower. When the bromine in the liquid phase drops to 150 mg / L, it is automatically transferred to resin adsorption.

[0067] (5) Air blowing and chemical absorption of sulfur dioxide: Same as step (5) in Example 1.

[0068] (6) Two-stage elution: The only difference from step (6) in Example 1 is that the resin space velocity is 1 BV / h and the elution is performed in stages with 5% sodium hydroxide at 45°C.

[0069] (7) Two-stage bromine oxidation and steam distillation: Same as step (7) in Example 1.

[0070] The testing conditions were the same as in Example 1. Operational results: The air blowing stage handled over 95% of the bromine recovery, with the blower operating in a high bromine concentration range, resulting in the lowest unit energy consumption. Resin adsorption only processed the low-bromine residue (≈150 mg / L) after blowing, resulting in low resin load and a significantly extended regeneration cycle. The overall bromine recovery rate was approximately 93%, comparable to Example 1, verifying the engineering feasibility of setting the upper limits of C1=300 mg / L and C2=150 mg / L. The design logic of prioritizing air blowing of high-concentration bittern and transferring low-concentration residue to resin performed excellently under this configuration.

[0071] Example 6: Medium-concentration mixed brine (dual-path balanced distribution) The raw material is a medium-concentration brine blended from various bromine-containing ingredients, with an average bromide ion concentration of approximately 550 mg / L, simulating a multi-source raw material mixing scenario in actual production. The configuration is set as C1=200 mg / L and C2=80 mg / L (center value). Specific operations are as follows: (1) Raw material pretreatment and acidification: Same as step (1) in Example 1.

[0072] (2) In-situ chlorine and alkali production by membrane electrolysis: The only difference from step (2) in Example 1 is that the electrolyzer uses an asbestos-free perfluorinated composite membrane for caustic soda production to separate the anode and cathode chambers; the current density is 50 A / dm³. 2 The cathode produces a 4.5% sodium hydroxide alkaline solution.

[0073] (3) Bromine oxidation: Same as step (3) in Example 1.

[0074] (4) Online detection and classification of bromine concentration: The bromine in the oxidized product is 480~680 mg / L, and all of it is ≥200 mg / L. It enters the air blowing tower, and the bromine in the tower drops to 80 mg / L and is then transferred to resin adsorption.

[0075] (5) Air blowing and chemical absorption of sulfur dioxide: Same as step (5) in Example 1.

[0076] (6) Two-stage segmented elution: The only difference from step (6) of Example 1 is that the resin space velocity is 5 BV / h, and elution is performed with 4.5% sodium hydroxide at 40°C.

[0077] (7) Two-stage bromine oxidation and steam distillation: Same as step (7) of Example 1.

[0078] The detection conditions are the same as those in Example 1. Operation effects: The comprehensive recovery rate of bromine is about 93%; compared with the single air blowing process (traditional recovery rate 80%), the recovery rate is increased by about 13 percentage points; compared with the single resin adsorption process, the resin treatment capacity is reduced by about 60% (since most of the bromine has been recovered in the air blowing section), the resin regeneration frequency is lowered, and the wear loss is reduced; the power consumption of the fan is reduced by about 35% compared with the full air blowing process (the process switches to the resin step when the blowing end point C2=80 mg / L, avoiding ineffective aeration in the low concentration section).

[0079] Example 7 A system for implementing the electrochemical in-situ chlorine and alkali production coupled concentration grading dual-path closed-loop bromine extraction process method according to any one of Examples 1 to 6, comprising a raw material buffer tank, a membrane electrolysis unit, a cathode self-produced alkali storage tank, an oxidation tower, an air blowing unit (air blowing tower), an absorption tower and an absorption completed liquid tank, a distillation tower, a resin adsorption unit and a parameter configuration module.

[0080] The membrane electrolysis unit adopts an anode chamber and a cathode chamber of a two-chamber electrolytic cell separated by a perfluorosulfonic acid-perfluorocarboxylic acid composite cation exchange membrane, and is equipped with an anolyte preparation tank and a catholyte preparation tank for feeding the anode chamber and the cathode chamber respectively; the output end of the anolyte preparation tank is communicated with the feeding pipeline of the anode chamber, the output end of the catholyte preparation tank is communicated with the feeding pipeline of the cathode chamber, the gas phase output pipeline of chlorine gas in the anode chamber is divided into two paths, which are respectively communicated with the gas phase feed inlets of the oxidation tower and the distillation tower; the discharge pipeline of the alkali solution in the cathode chamber is communicated with the feed inlet of the cathode self-produced alkali storage tank; the cathode self-produced alkali storage tank is provided with two independent alkali solution distribution pipelines, one path is supplied to the acidic tail liquid neutralization section of the resin adsorption unit, and the other path is supplied to the alkali solution segmented elution section.

[0081] A first-stage online bromine concentration detection diverter valve is assembled on the liquid phase discharge pipeline of the oxidation tower, and a first-stage demarcation concentration C1 configuration module is built in the valve group; the valve group is provided with two discharge branches, which are respectively communicated with the air blowing unit and the resin adsorption unit.

[0082] The air blowing unit is an air blowing tower, a second-stage bromine concentration online monitoring component is arranged inside the tower, a second-stage material transfer concentration C2 configuration module is built in, and the system program forcibly locks C2<C1; the air blowing tower is provided with a low-bromine residual liquid outlet and a bromine vapor gas phase outlet, and the low-bromine residual liquid outlet in the tower is conveyed to the resin adsorption unit through a material transfer pipeline; the resin adsorption unit is provided with a special buffer tank for the low-concentration bromine eluent, the high-concentration bromine eluent pipeline is connected to the absorption completed liquid tank, the low-concentration bromine eluent is first sent to the buffer tank for buffering, and then returned to the front end of the resin elution section to be recycled as a pre-elution medium.

[0083] The distillation column is connected to the anodic chlorine gas delivery pipeline of the membrane electrolysis unit and the steam supply pipeline; a finished bromine discharge port is arranged at the top of the distillation column, the discharge pipeline of the absorption completed liquid pool is connected to the distillation column, and the distillation tail liquid discharged from the bottom of the distillation column flows back to the acidification pipeline at the front end of the raw material cache for recycling.

[0084] The resin adsorption unit is provided with a low-bromine residual liquid feed port, a two-stage alkali elution section, a low-concentration bromine eluent buffer tank, a high-concentration bromine eluent outlet, and an acidic tail liquid discharge port; the high-concentration bromine eluent pipeline is connected to the absorption completed liquid pool; the low-concentration bromine eluent outlet is communicated with the buffer tank, and the discharge pipeline of the buffer tank flows back to the front end of resin elution to be used as the pre-elution medium for the next round; the acidic tail liquid pipeline is connected to the neutralization branch of the cathode self-produced alkali storage tank, and the waste liquid after neutralization is discharged up to the standard.

[0085] The system has a built-in parameter configuration module, which includes a threshold logic judgment unit and an execution signal output unit, and can independently adjust the first-stage cutoff concentration C1 and the second-stage transfer concentration C2 online. The program forcibly locks C2<C1, and the C2 judgment logic only takes effect for the transfer logic of the low-bromine residual liquid discharged from the air blowing unit.

[0086] Comparative Example 1: Traditional single resin adsorption process (no in-situ chlorine and alkali production by electrolysis, no dual paths) The raw materials are the same as those in Example 1, and the process flow is as Figure 2 shown. The whole set of process has no membrane electrolysis chlorine and alkali production unit, no two-stage bromine concentration intelligent shunting, no closed loop of high and low bromine eluent in separate paths, all liquid chlorine, caustic soda and sulfuric acid are purchased externally throughout the process, and independent acidolysis bromine equipment is added. The specific operation steps are as follows: (1) Raw material pretreatment and acidification: After the raw material is filtered to remove suspended salt mud impurities, it is synergistically acidified online to pH≈3.0 by the distillation tail liquid and externally purchased sulfuric acid.

[0087] (2) Oxidation of bromide ions by externally purchased liquid chlorine: A high-pressure liquid chlorine storage tank, a gasification device and a safety absorption tower are supporting facilities. The externally purchased industrial liquid chlorine is gasified and then introduced into the acidified raw material, and chlorine gas oxidizes bromide ions in the raw material to elemental bromine.

[0088] (3) Single resin adsorption: All the oxidized high-bromine raw materials are directly and fully passed into the adsorption column filled with SP207 brominated modified macroporous resin (the same as in Example 1), with an adsorption space velocity of 1 BV / h; the load of high-concentration bittern is extremely high, the resin is quickly penetrated and saturated in a short time, and the adsorption column needs to be switched frequently for regeneration.

[0089] (4) Neutralization and direct discharge of adsorption tail liquid with externally purchased alkali: 30% industrial sodium hydroxide is separately purchased to prepare 5% neutralization liquid, the acidic tail liquid discharged after adsorption by the resin column is adjusted online to pH 7~8 with the neutralization liquid, and the waste water after neutralization is directly discharged outside.

[0090] (5) Purchased caustic soda to elute the resin in one go: After the resin adsorption is completed, a 5% alkali solution prepared with purchased industrial sodium hydroxide is used to elute the entire resin in one go.

[0091] (6) Eluent acid hydrolysis alone + secondary bromine blowing: The eluent is sent to an independent acid hydrolysis reactor, and purchased sulfuric acid is added for reverse disproportionation to release bromine. The bromine is then obtained by steam distillation and rectification. The distillation tail liquid is refluxed to the upstream raw material acidification process.

[0092] The testing conditions were the same as in Example 1. Operating results: The overall bromine recovery rate was only about 85%; it continuously consumed large amounts of liquid chlorine, purchased caustic soda, and sulfuric acid; the resin regeneration frequency was high, and resin wear and loss were significant; it lacked a two-stage gradient diversion structure, making it unsuitable for the economical treatment of high-concentration bittern raw materials (the entire load was on the resin); the overall operating cost was about 32% higher than in Example 1.

[0093] Comparative Example 2: Traditional single air blowing process (no electrolysis, no dual-path, no resin adsorption) The raw materials are the same as in Example 2, and the process flow is as follows: Figure 3 As shown. The entire process has no electrolysis unit, no resin coupling recycling, and only a single air blowing main line. The specific steps are as follows: (1) Raw material pretreatment and acidification: Same as step (1) of Comparative Example 1.

[0094] (2) Purchased liquid chlorine oxidizes bromide ions: Same as step (2) of Comparative Example 1.

[0095] (3) Single air blowing: After oxidation, all raw materials are sent to the air blowing tower; because the bromine concentration of the raw materials is low and the partial pressure of bromine gas phase is low, room temperature air must be continuously blown in at full load for a long time to blow out bromine vapor.

[0096] (4) Absorption and enrichment of sulfur dioxide in bromine-containing tail gas: Bromine vapor at the top of the blow-out tower is absorbed in the opposite direction with sulfur dioxide flue gas to obtain acidic bromine-containing absorbent liquid; the low-bromine acidic residue at the bottom of the air blow-out tower is neutralized online with 5% alkaline solution prepared with purchased 30% industrial sodium hydroxide and then discharged without any recycling mechanism.

[0097] (5) Secondary oxidation and distillation of the absorbent: The absorbed liquid is oxidized by the external liquid chlorine and then steam distilled and purified to produce bromine product; the distillation tail liquid at the bottom of the distillation tower is recycled to the raw material acidification pipeline.

[0098] The testing conditions were the same as in Example 1. Operational results: The overall bromine recovery rate was only about 78%; large quantities of purchased sulfuric acid, liquid chlorine, and caustic soda were continuously consumed, resulting in reagent and operating costs that were approximately 22% higher than in Example 2; the plant area faced safety and environmental risks related to high-pressure storage and transportation of liquid chlorine, leakage, and explosion; and a large amount of low-bromine residual liquid was directly discharged, causing a waste of bromine resources and potential environmental risks.

[0099] The embodiments of the present invention have been shown and described above. Those skilled in the art can make improvements or modifications based on the above description. For example, the high-concentration bromine eluent is first reacted with magnesium chloride or bittern to recover the alkali in the eluent and produce magnesium hydroxide as a byproduct, while simultaneously reducing the subsequent neutralization acid consumption; segmented elution is not used, and all eluent is mixed with the absorption solution; sulfuric acid dioxide absorption is replaced with sodium hydroxide alkali absorption; the membrane electrolysis unit is eliminated, and purchased chlorine gas and sodium hydroxide are used for concentration-fractionated dual-path closed-loop bromine extraction, etc. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A closed-loop bromine extraction process with electrochemical in-situ chlorination and alkali production coupled with concentration-stage dual pathways, characterized in that, comprising the following steps: (1) Raw material pretreatment and acidification: After the bromine-containing raw material is filtered to remove suspended impurities, it is sent to the oxidation tower after being subjected to synergistic in-line acidification by the steam distillation tail liquid and sulfuric acid; (2) In-situ chlorine and alkali production by membrane electrolysis: Prepare sodium chloride brine and feed it into the anode of a membrane-separated two-chamber electrolytic cell, prepare sodium chloride or / and sodium hydroxide solution and feed it into the cathode of the two-chamber electrolytic cell for electrolysis; (3) First-stage bromine oxidation: The chlorine gas produced in the anode chamber of the electrolytic cell is fed into the oxidation tower, where it is in full countercurrent contact with the acidified bromine-containing raw material, and bromide ions in the raw material are oxidized to bromine elemental substance by the chlorine gas; (4) In-line bromine concentration detection and gradient classification two-path automatic splitting: A first-stage in-line bromine concentration detection device is arranged on the discharge pipeline of the oxidation tower, which supports in-line setting of the first-stage cut-off concentration C1, a second-stage in-line bromine concentration detection device is arranged inside the liquid phase of the air blowing tower, which supports in-line setting of the second-stage transfer concentration C2, and the system program mandatorily restricts C2<C1; the system is provided with two paths of air blowing and resin adsorption, and automatic splitting is performed according to the comparison result between the detected concentration and the set cut-off concentration; when the bromine concentration at the discharge port of the oxidation tower is ≥C1, the material is automatically split to the air blowing path for main blowing; when the bromine concentration in the air blowing tower drops to C2, the material is automatically transferred to the resin adsorption path; when the bromine concentration at the discharge port of the oxidation tower is <C1, the material is automatically split to the resin adsorption path to capture liquid-phase bromine; (5) Chemical absorption: The bromine vapor blown out from the air blowing tower in step (4) is mixed with sulfur dioxide flue gas and then fed into the absorption tower for countercurrent reaction, so as to obtain an acidic high-concentration bromine absorption finished liquid, which is stored in an absorption finished liquid tank; (6) Sectional elution of resin by cathode self-produced lye: The adsorbed bromine-loaded resin is pre-eluted with the buffered and circulated low-concentration bromine eluent to remove the bromine components on the surface layer of the resin, and then fresh lye from the self-produced lye storage tank is introduced for deep elution; (7) Second-stage bromine oxidation and steam distillation: The pH of the absorption finished liquid is monitored in real time, and sulfuric acid is added for acidification when the pH>3.5; the acidified bromine-containing liquid is fed into the distillation tower, mixed with the chlorine gas produced at the anode of the electrolytic cell for oxidation, and refined by steam distillation and rectification to obtain an industrial bromine product.

2. The process method according to claim 1, characterized in that, The automatic splitting logic of step (4) is as follows: ① When the bromine concentration at the discharge port of the oxidation tower is ≥C1, the material is automatically split to the air blowing path for air blowing to obtain bromine vapor; the liquid-phase bromine concentration in the air blowing tower is monitored in real time, and when the bromine concentration in the tower drops to C2, the material is automatically transferred to the resin adsorption path; the acidic tail liquid discharged after the resin adsorbs bromine is neutralized with the lye from the self-produced lye storage tank to meet the discharge standard and then discharged; C1 is 50~300 mg / L; C2 is 15~150 mg / L; ② When the bromine concentration at the discharge port of the oxidation tower is <C1, the material is automatically split to the resin adsorption path to capture liquid-phase bromine.

3. The process method according to claim 1, characterized in that, The mass fraction of sodium chloride brine at the anode of the two-chamber electrolytic cell is 5%~28%; the mass fraction of sodium chloride or / and sodium hydroxide solution at the cathode of the two-chamber electrolytic cell is 0.1%~5%; the anode adopts a selective chlorine evolution electrode, which electrochemically oxidizes chloride ions to generate chlorine gas; the cathode synchronously produces sodium hydroxide lye which is collected into the self-produced lye storage tank.

4. The process method according to claim 1, characterized in that, In step (2), the membrane is a diaphragm or ion exchange membrane used in caustic soda production; during electrolysis, the anode working potential is controlled at 1.25~1.45 V vs SHE, and the current density is 20~100 A / dm³. 2 .

5. The process method according to claim 1, characterized in that, Step (2) The cathode produces sodium hydroxide alkaline solution with a mass fraction of 1%~10%. The self-produced alkali storage tank is equipped with two independent distribution pipelines, which are used for the resin adsorption tail liquid neutralization process and the bromine-loaded resin segmented elution process, respectively.

6. The process method according to claim 1, characterized in that, In step (1), the online acidification pH is 3.0~4.

0.

7. The process method according to claim 1, characterized in that, In step (6), the resin adsorption space velocity is 1~5 BV / h; the elution operation parameters are: the mass fraction of the self-produced alkaline solution at the cathode is 1%~10%, the elution space velocity is 0.5~1.5 BV / h, and the elution temperature is controlled at room temperature to 60℃; the alkaline high-concentration bromine eluent generated in step (6) is sent to the absorption completion liquid pool and mixed with the acidic absorption completion liquid; the low-concentration bromine eluent is sent to the buffer tank for buffering and is circulated as the resin pre-elution medium for the next round.

8. The process method according to claim 1, characterized in that, The bromine-containing raw materials include any one or more mixed raw materials such as seawater, concentrated seawater by-products of seawater desalination, sea salt bittern, low-concentration bromine-containing chemical wastewater, underground brine, and bromine-containing formation water from oil fields.

9. A system for implementing the electrochemical in-situ chlorination and alkali production coupled concentration-stage dual-path closed-loop bromine extraction process according to any one of claims 1 to 8, characterized in that, include: The raw material buffer tank has its input end connected to a bromine-containing raw material conveying pipeline, and its discharge pipeline is equipped with an online sulfuric acid mixing pipeline. The membrane electrolysis unit includes a dual-chamber electrolytic cell with an anode chamber and a cathode chamber separated by a diaphragm or ion exchange membrane used in caustic soda production, and is equipped with an anode solution preparation tank and a cathode solution preparation tank. The output end of the anode solution preparation tank is connected to the feed pipeline of the anode chamber; the output end of the cathode solution preparation tank is connected to the feed pipeline of the cathode chamber; a selective chlorine evolution electrode is installed in the anode chamber; the gas phase output pipeline of chlorine in the anode chamber is divided into two paths, which are respectively connected to the gas phase feed ports of the oxidation tower and the distillation tower; the alkali solution outlet pipeline of the cathode chamber is connected to the feed port of the cathode self-produced alkali storage tank. The cathode has its own alkali storage tank, which is equipped with two independent alkali distribution pipelines, which are respectively connected to the tail liquid neutralization section of the resin adsorption unit and the alkali segmented elution section. The oxidation tower is equipped with a primary online bromine concentration detection diversion valve group on its liquid phase discharge pipeline. The valve group has two discharge branches, which are respectively connected to the feed end of the air blowing unit and the feed end of the resin adsorption unit. The air blowing unit is equipped with a secondary bromine concentration online monitoring component and a built-in secondary transfer concentration C2 configuration module; the air blowing unit has a low bromine residual liquid outlet and a bromine vapor phase outlet; the low bromine residual liquid outlet is connected to the resin adsorption unit inlet through the transfer pipeline; the bromine vapor phase outlet is connected to the absorption tower inlet pipeline. The absorption tower and the absorption completed liquid pool are equipped with a sulfur dioxide inlet pipe, and the liquid phase discharge of the absorption tower is connected to the absorption completed liquid pool. The absorption liquid pool is equipped with a sulfuric acid dosing pipeline; the absorption liquid pool discharge pipeline is connected to the feed inlet of the distillation tower. The distillation column is connected to the chlorine gas delivery pipeline and steam supply pipeline of the membrane electrolysis unit anode; the top of the distillation column is equipped with a bromine product outlet, and the bottom of the distillation column discharges the distillation tail liquid and returns it to the acidification pipeline at the front end of the raw material buffer for recycling. Resin adsorption unit, which is respectively provided with a low-bromine residual liquid feed port, a two-stage alkaline desorption section, a low-concentration bromine eluent buffer tank, a high-concentration bromine eluent outlet, and an acidic tail liquid discharge port; the high-concentration bromine eluent pipeline is connected to the absorption completed liquid tank; the low-concentration bromine eluent outlet is in communication with the buffer tank, and the discharge pipeline of the buffer tank flows back to the front end of resin desorption to be used as the pre-desorption medium for the next round; the acidic tail liquid pipeline is connected to the neutralization branch of the cathode self-produced alkali storage tank, and the waste liquid after neutralization is discharged up to the standard; The system has a built-in parameter configuration module, which includes a threshold logic judgment unit and an execution signal output unit.

10. The system of the electrochemical in-situ chlorine and alkali production coupled concentration-stage dual-path closed-loop bromine extraction process according to claim 9, characterized in that, The built-in parameter configuration module of the system independently adjusts the first-stage cut-off concentration C1 and the second-stage transfer concentration C2 online, the program forcibly locks C2<C1, and the C2 judgment logic only takes effect for the transfer operation of the low-bromine residual liquid discharged from the air blowing-out unit.

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