Bromine extraction system and method for brominated flame retardant washing wastewater

Abstract

The invention belongs to the field of wastewater treatment and resource utilization, and discloses a bromine extraction system and method for brominated flame retardant washing wastewater. In the system, a bromine washing wastewater storage tank is connected with a water inlet of a raw water tank of a nanofiltration device, a nanofiltration produced water outlet of the nanofiltration device is connected with a water inlet of a raw water tank of a first reverse osmosis device, a concentrated water outlet of the first reverse osmosis device is connected with an inlet of a feeding pump of an MVR evaporator device, and a mother liquor outlet of the MVR evaporator device is connected with an inlet of a rich bromine storage tank; a pipeline connected with an outlet of the rich bromine storage tank and an acid adding pipeline are converged and then are connected with a middle water inlet of the ozone oxidation tower through a mixer, a lower water outlet of the ozone oxidation tower is connected with a middle-upper feed port of the distillation tower, and a top recovery port of the distillation tower is connected with an inlet of the bromine storage tank. According to the method, the resource recycling of the bromide ions in the washing wastewater in the production of the tetrabromobisphenol A can be realized.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment and resource utilization, and more specifically, relates to a bromine extraction system and method for bromine-based flame retardant washing wastewater. Background Technology

[0002] Bromine is mainly extracted from the ocean, underground brine, and oil and gas fields, and the extraction process is complex. Bromine distribution is relatively concentrated, with over 90% of bromine produced within a single province. As a non-renewable resource in nature, bromine's reserves are dwindling. However, as an indispensable production material in modern industrial processes, the future demand for bromine will continue to grow. Therefore, the recycling and utilization of bromine resources is becoming increasingly important.

[0003] According to the latest survey report on the use of bromine resources, nearly 40% of bromine is used in the production of flame retardants. Tetrabromobisphenol A (TBBPA), as the mainstream bromine flame retardant, is currently mostly produced using the hydrogen peroxide bromination method. This involves using chlorobenzene as a solvent, and under the oxidation of H₂O₂, bisphenol A undergoes a bromination reaction to produce TDBPA. The wastewater discharged from TDBPA production mainly consists of three parts: First, the acidic water discharged after the bromination reaction is completed, which is neutralized with alkali and then discharged into a subsequent treatment tank; second, the chlorobenzene phase solution after separation is treated with sodium sulfite, resulting in stratification, which is then separated to form a second type of wastewater; third, the wash water formed after the chlorobenzene phase solution is washed three times with hot water. This wastewater is alkaline and contains many dissolved reaction products and byproducts, making it extremely complex.

[0004] For the wastewater from the above-mentioned tetrabromobisphenol A washing process, since the tetrabromobisphenol A washing process requires two sodium sulfite washes and three deionized water washes, the concentration of bromide ions in the discharged wastewater can reach 800-1000 mg / L, mainly in the form of sodium bromide. Other pollutants in the water are relatively few, with only 3000-5000 mg / L sulfate and 2000-3000 mg / L COD.

[0005] In addition, the main methods for extracting bromine currently include the following: In the steam distillation method, the brine is acidified and enters a packed column. In the column, bromide ions are oxidized into free bromine by countercurrent chlorine gas. Then, the bromine is distilled off in a condenser by taking advantage of the difference in volatility between water and bromine. The bromine product is obtained by allowing the distillate to settle and separate into layers. In the air-blowing method, bromide ions in the brine are oxidized by chlorine gas to form elemental bromine, which is then blown out of the brine by air. After absorption by an absorbent, chlorine gas is added, and the free bromine is separated by water vapor. The bromine is then condensed to obtain bromine. The air-blowing method is further divided into two processes: acidification absorption and alkaline absorption. In the ion exchange adsorption method, bromide ions are oxidized to free bromides during chlorination and oxidation, which are then absorbed by the ion exchange resin. The loaded resin can then desorb the bromide ions using H₂SO₃ and accept them. Finally, hydrochloric acid is used to elute the bromide ions adsorbed in the resin, and the eluent is oxidized by chlorine and then steam distilled to obtain the final product.

[0006] Of the three methods mentioned above, only steam distillation and air blowing have been industrially applied, but both have their limitations. Steam distillation is suitable for scenarios with bromine content greater than 3 g / L, but it is generally difficult for bromine in the extract to reach this concentration. Currently, over 90% of bromine extraction uses air blowing, but this method has disadvantages such as high acid and alkali consumption and high energy consumption.

[0007] Therefore, there is an urgent need to propose a bromine extraction system and method for bromine-based flame retardant washing wastewater. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by proposing a bromine extraction system and method for wastewater from the production of brominated flame retardants. This invention enables the resource recovery of bromide ions from the wastewater used in the production of tetrabromobisphenol A.

[0009] To achieve the above objectives, the present invention provides a bromine extraction system for washing wastewater containing bromine-based flame retardants, the system comprising a bromine removal and concentration unit and a bromine extraction unit; The bromine removal and concentration unit includes: a bromine washing wastewater storage tank, a nanofiltration unit, a first reverse osmosis unit, and an MVR evaporator unit; The bromine extraction unit includes: a bromine-rich storage tank, an ozone oxidation tower, an acid addition pipeline, a mixer, a distillation tower, a second reverse osmosis unit, a reduction reaction tank, and a bromine storage tank; the ozone oxidation tower is equipped with a central water inlet, a lower ozone gas inlet, and a lower drain outlet; the distillation tower is equipped with a middle-upper feed inlet, a top collection outlet, a bottom discharge outlet, and a central feed inlet; The outlet of the bromine washing wastewater storage tank is connected to the inlet of the raw water tank of the nanofiltration unit, the nanofiltration product water outlet of the nanofiltration unit is connected to the inlet of the raw water tank of the first reverse osmosis unit, the concentrate outlet of the first reverse osmosis unit is connected to the inlet of the feed pump of the MVR evaporator unit, and the mother liquor outlet of the MVR evaporator unit is connected to the inlet of the bromine-rich storage tank. The outlet pipeline of the bromine-rich storage tank is connected to the acid addition pipeline and then connected together to the middle water inlet of the ozone oxidation tower through a mixer. The lower drain outlet of the ozone oxidation tower is connected to the upper middle feed inlet of the distillation tower, and the top collection port of the distillation tower is connected to the inlet of the bromine storage tank. The bottom discharge port of the distillation column is connected to two pipelines. One pipeline is connected to the inlet of the raw water tank of the second reverse osmosis unit, and the concentrate outlet of the second reverse osmosis unit is connected to the middle feed port of the distillation column through the reduction reaction tank.

[0010] In this invention, the nanofiltration device, reverse osmosis device, and MVR evaporator device are all devices known to those skilled in the art, such as: The equipment connections within the nanofiltration unit are as follows: raw water tank - raw water pump - multi-media filter - security filter - dosing device (online mixing) - high-pressure pump - nanofiltration membrane housing (membrane element) - two outputs, one for nanofiltration concentrate and the other for nanofiltration permeate containing sodium bromide. In this invention, as a preferred embodiment, the outlet of the bromine washing wastewater storage tank is connected to the inlet of the raw water tank of the nanofiltration unit via a water pump.

[0011] The equipment connections within the reverse osmosis unit are as follows: raw water tank - raw water pump - multi-media filter - activated carbon filter - security filter - dosing device (online mixing) - high-pressure pump - reverse osmosis membrane housing (membrane element) - two outputs, one for the first reverse osmosis permeate and the other for reverse osmosis concentrate containing sodium bromide.

[0012] The equipment connections within the MVR evaporator unit are as follows: Raw material tank - Feed pump - Preheater - Filter - Evaporator heating chamber - Evaporator evaporation chamber - Gas-liquid separator - Two-way branch: Gas phase: Secondary steam - compressor compression - high temperature and high pressure steam - heating chamber (heat release and condensation) - condensate - condensate tank - reuse / discharge; Liquid phase: Concentrate - Crystallizer (optional) - Thickener - Centrifuge - Sodium bromide-containing mother liquor.

[0013] According to the present invention, preferably, the system further includes a waste liquid tank and a clean water storage tank; The other pipeline connecting the nanofiltration concentrate outlet of the nanofiltration unit and the bottom discharge port of the distillation column is connected to the waste liquid pool. The product water outlet of the first reverse osmosis unit, the product water outlet of the second reverse osmosis unit, and the secondary steam condensate outlet of the MVR evaporator unit are all connected to the clean water storage tank.

[0014] According to the present invention, preferably, a shell-and-tube condenser is provided at the top of the distillation column; the clear water storage tank is connected to the condenser tube of the shell-and-tube condenser at the top of the distillation column.

[0015] According to the present invention, preferably, the system further includes an ozone generator; the ozone generator is connected to the lower ozone inlet of the ozone oxidation tower.

[0016] According to the present invention, preferably, the ozone oxidation tower is further provided with a central reflux port, and the lower drain outlet of the ozone oxidation tower is divided into two paths, one of which is connected to the upper middle feed inlet of the distillation tower, and the other is connected to the central reflux port of the ozone oxidation tower (to realize internal circulation).

[0017] According to the present invention, preferably, the bottom ring of the distillation column is provided with a heat insulation jacket, and the heat insulation jacket is provided with a heat source inlet and a heat source outlet; The non-condensable gas outlet of the MVR evaporator is connected to the heat source inlet of the insulation jacket.

[0018] In this invention, the bromine washing wastewater storage tank, the bromine-rich storage tank, and the bromine storage tank are all made of glass-lined material.

[0019] Another aspect of the present invention provides a method for bromine extraction from washing wastewater containing brominated flame retardants. The method employs the aforementioned system and includes the following steps: S1: The washing wastewater from the production of tetrabromobisphenol A is sent from the bromine washing wastewater storage tank to the nanofiltration unit. After nanofiltration treatment, nanofiltration concentrate and sodium bromide-containing nanofiltration permeate are obtained. The sodium bromide-containing nanofiltration permeate is sent to the first reverse osmosis unit. After first reverse osmosis treatment, first reverse osmosis permeate and sodium bromide-containing reverse osmosis concentrate are obtained. The sodium bromide-containing reverse osmosis concentrate is sent to the MVR evaporator unit. After evaporation and concentration treatment, non-condensable gas, secondary steam condensate, and sodium bromide-containing mother liquor are obtained. The sodium bromide-containing mother liquor is sent to the bromine-rich storage tank. S2: The sodium bromide mother liquor in the bromine-rich storage tank is mixed with acid and then fed into the ozone oxidation tower. After ozone oxidation treatment, a feed liquid containing elemental bromine and bromate is obtained. The feed liquid containing elemental bromine and bromate is fed into the distillation tower. After distillation treatment, bromine is obtained at the top of the distillation tower and a residual liquid containing bromate is obtained at the bottom of the distillation tower. S3: The bromine is sent to the bromine storage tank for storage; a portion of the residual liquid containing bromate is sent to the second reverse osmosis unit for second reverse osmosis treatment to obtain second reverse osmosis permeate and bromate-containing reverse osmosis concentrate; the bromate-containing reverse osmosis concentrate is sent to the distillation tower for distillation treatment after reduction treatment.

[0020] In this invention, the washing wastewater from the production of tetrabromobisphenol A is collected and introduced into a bromine washing wastewater storage tank. The washing wastewater in the bromine washing wastewater storage tank has a relatively simple composition, with the main pollutants being sulfate, COD and sodium bromide.

[0021] The washing wastewater from the production of tetrabromobisphenol A is first pumped into the nanofiltration unit. After being pressurized by the raw water pump and high-pressure pump of the nanofiltration unit, it is separated by the nanofiltration membrane. Sulfate and a large amount of COD are intercepted by the nanofiltration membrane, forming nanofiltration concentrate which is discharged into the waste liquid tank. Sodium bromide in the washing wastewater can permeate through the nanofiltration membrane into the nanofiltration permeate, and at the same time, sodium bromide in the nanofiltration permeate can be concentrated.

[0022] Nanofiltration permeate enters the first reverse osmosis unit, where sodium bromide can be intercepted by the reverse osmosis membrane. Sodium bromide is mainly enriched in the reverse osmosis concentrate. The concentration factor of sodium bromide is adjusted by adjusting the reverse osmosis recovery rate. The reverse osmosis permeate is collected in a clear water storage tank. The sodium bromide-containing reverse osmosis concentrate is collected and then enters the MVR evaporator unit for further concentration.

[0023] In the MVR evaporator, the sodium bromide-containing reverse osmosis concentrate is concentrated after evaporation. Simultaneously, the sodium bromide-containing reverse osmosis concentrate may contain small amounts of organic substances such as chlorobenzene. These organic substances can form azeotropes with water during evaporation, thereby removing the organic matter. The secondary steam generated by the MVR evaporator is condensed to produce condensate, which is collected in a clean water storage tank. The non-condensable gas generated by the MVR evaporator carries a certain calorific value and is introduced into the insulation jacket at the bottom of the distillation column to exchange heat with the feed liquid inside the column. After the sodium bromide-containing mother liquor produced by the MVR evaporator reaches a certain concentration factor, the sodium bromide concentration in the mother liquor can reach 50-100 g / L.

[0024] Sodium bromide-containing mother liquor is collected in a bromine-rich storage tank. Then, the sodium bromide-containing mother liquor in the bromine-rich storage tank is mixed with acid (the pH of the mixture of sodium bromide-containing mother liquor and acid is 2-4) and sent to the ozone oxidation tower. Inside the ozone oxidation tower, bromide ions undergo a series of reactions with ozone: Br - +O3—BrO - +O2, this reaction is a rate-determining step, and the reaction rate is significantly affected by pH value; Acid-base balance: BrO - +H + —HOBr, under acidic conditions, HOBr is the main form; Secondary reaction: HOBr+H + +Br - —Br2+H2O, this reaction proceeds rapidly at pH <4, producing elemental bromine; Competitive response: BrO - +O3—BrO2 - +O2; BrO2 - +O3—BrO3 - +O2.

[0025] Inside the ozone oxidation tower, after sodium bromide is oxidized by ozone, bromide ions mainly exist in the form of elemental bromine, with a small amount of bromate also present.

[0026] A feed solution containing elemental bromine and bromate is pumped into a distillation column. The feed solution is heated to 60-70°C for distillation. The elemental bromine turns into bromine vapor upon heating. The bromine vapor exchanges heat with the condenser at the top of the distillation column, and after cooling, forms bromine, which is collected and stored in a bromine storage tank. This invention can control the bromine extraction rate in the distillation column to ≥90%. After reaching the required extraction rate, bromate will be further enriched in the residual liquid at the bottom of the distillation column. A portion of the residual liquid containing bromate is discharged to a waste liquid tank, while another portion is pumped into a second reverse osmosis unit. After reverse osmosis concentration, the bromate on the reverse osmosis concentrate side is enriched and discharged into a reduction reaction tank, while the reverse osmosis permeate is discharged into a clear water storage tank.

[0027] Inside the reduction reaction vessel, bromate ions react with the reducing agent (sodium sulfite) under acidic conditions as follows: BrO3 - +5Br - +6H + —3Br2+3H2O, the reduced liquid is fed back into the distillation tower for bromine extraction.

[0028] According to the present invention, preferably, the method further includes: The nanofiltration concentrate and the remaining portion of the bromate-containing residual liquid are discharged into a waste liquid tank; The first reverse osmosis permeate, the second reverse osmosis permeate, and the secondary steam condensate are discharged into a clear water storage tank. Then, the water in the clear water storage tank is sent into the condenser tube of the shell-and-tube condenser at the top of the distillation column as a cold source for condensing bromine vapor, thereby obtaining bromine at the top of the distillation column. The non-condensable gas is fed into the insulation jacket surrounding the bottom of the distillation column, serving as a heat source for heat exchange with the liquid feed inside the column. In this invention, the liquid discharged from the heat source outlet of the insulation jacket is directly discharged from the system and then adsorbed by activated carbon before being discharged from the system.

[0029] According to the present invention, preferably, the water quality conditions of the washing wastewater for producing tetrabromobisphenol A include: bromide ion concentration of 800-1000 mg / L, sulfate concentration of 3000-5000 mg / L, and COD concentration of 2000-3000 mg / L.

[0030] According to the present invention, preferably, the nanofiltration recovery rate of the nanofiltration treatment is 50-70%.

[0031] According to the present invention, preferably, the reverse osmosis recovery rate of the first reverse osmosis treatment is 75-80%.

[0032] According to the present invention, preferably, the evaporation temperature of the evaporation concentration treatment is 90-95°C, and the concentration ratio (referring to the ratio of the total mass of sodium bromide-containing reverse osmosis concentrate to the mass of sodium bromide-containing mother liquor) is 5-10 times.

[0033] According to the present invention, preferably, the concentration of sodium bromide in the sodium bromide-containing mother liquor is 50-100 g / L.

[0034] According to the present invention, preferably, the pH of the solution after mixing sodium bromide mother liquor and acid in the bromine-rich storage tank is 2-4.

[0035] According to the present invention, preferably, the ozone concentration in the ozone oxidation tower is controlled at 80-100 mg / L, and the ozone intake rate is 100-150 Nm³. 3 / h; the temperature inside the ozone oxidation tower is ≤25℃.

[0036] According to the present invention, preferably, the temperature of the feed liquid in the distillation column is 60-70°C; and the bromine extraction rate at the top of the distillation column is ≥80%.

[0037] According to the present invention, preferably, the reverse osmosis recovery rate of the second reverse osmosis treatment is 45-55%.

[0038] According to the present invention, preferably, the reducing agent used in the reduction treatment is sulfite.

[0039] The beneficial effects of the technical solution of this invention are as follows: This invention targets the washing wastewater in the tetrabromobisphenol A production process (the washing wastewater has low organic bromine content, high bromide ion content, and the main salt is sulfate, with relatively low COD, making it suitable for bromine resource recovery). It converts and extracts bromide ions from the washing wastewater into bromine, achieving not only efficient removal of pollutants from the wastewater but also the regeneration and utilization of bromine in the wastewater; specifically: 1. Nanofiltration can remove sulfate and most of the COD from water. The main substance in nanofiltration product water is sodium bromide.

[0040] 2. Sodium bromide can be further concentrated through the first reverse osmosis, reducing the throughput of the MVR evaporator and lowering energy consumption.

[0041] 3. Some organic compounds such as chlorobenzene mixed in with sodium bromide reverse osmosis concentrate undergo azeotropic reaction with water during MVR evaporation, achieving efficient removal of organic impurities. MVR evaporation can further purify and concentrate sodium bromide-containing reverse osmosis concentrate. Through a series of concentrations, the bromide ion concentration can be concentrated to 50-100 g / L. The higher the bromide ion concentration, the better the mass transfer effect of ozone oxidation, thereby reducing the energy consumption of subsequent bromide ion oxidation.

[0042] 4. Utilizing ozone to oxidize bromide ions is more environmentally friendly to workers and the surrounding environment compared to traditional chlorine oxidation. Controlling the pH of the solution entering the ozone oxidation tower ensures that bromide ions are oxidized into elemental bromine, effectively suppressing the side reaction of producing bromate during ozone oxidation. The oxidation of bromide ions and the distillation of bromine are carried out in steps, avoiding ozone decomposition caused by high feed temperature during distillation, thus improving ozone utilization and saving energy.

[0043] 5. The bromate ions generated by ozone oxidation in the distillation column cannot be distilled. After distillation, the residual liquid in the distillation column contains a large amount of bromate ions. After the second reverse osmosis concentration treatment, the bromate ions react with the added sulfite in the reduction reaction tank to generate elemental bromine, which can be further sent to the distillation column for distillation, thus improving the bromine extraction rate.

[0044] 6. Simultaneously, the permeate from RO (reverse osmosis) and the condensate from the secondary steam generated by MVR evaporation can be used as cooling water for the distillation column (for condensing the gas at the top of the distillation column), reducing water waste. The non-condensable gas generated by MVR evaporation is introduced into the insulation jacket at the bottom of the distillation column to heat the feed liquid inside the column, realizing the utilization of waste heat.

[0045] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0046] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the invention.

[0047] Figure 1 A schematic diagram of a bromine extraction system for washing wastewater containing bromine-based flame retardants, provided in Embodiment 1 of the present invention, is shown.

[0048] The annotations in the attached figures are explained as follows: 1. Bromine washing wastewater storage tank; 2. Nanofiltration unit; 3. First reverse osmosis unit; 4. MVR evaporator unit; 5. Bromine-rich storage tank; 6. Ozone oxidation tower; 7. Acid addition pipeline; 8. Mixer; 9. Distillation tower; 10. Second reverse osmosis unit; 11. Reduction reaction tank; 12. Bromine storage tank; 13. Clean water storage tank. 2.1 Nanofiltration concentrate, 2.2 Nanofiltration permeate containing sodium bromide; 3.1 First reverse osmosis permeate; 3.2 Reverse osmosis concentrate containing sodium bromide; 4.1 Secondary steam condensate; 4.2 Sodium bromide-containing mother liquor; 9.1 Residual solution containing bromate; 10.1 Second reverse osmosis permeate, 10.2 Bromate-containing reverse osmosis concentrate. Detailed Implementation

[0049] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0050] Example 1

[0051] This embodiment provides a bromine extraction system for washing wastewater containing bromine-based flame retardants, such as... Figure 1 As shown, the system includes a bromine removal and concentration unit, a bromine extraction unit, a waste liquid tank (not shown), and a clean water storage tank 13; The bromine removal and concentration unit includes: a bromine washing wastewater storage tank 1, a nanofiltration device 2, a first reverse osmosis device 3, and an MVR evaporator device 4; The bromine extraction unit includes: a bromine-rich storage tank 5, an ozone generator (not shown), an ozone oxidation tower 6, an acid addition pipeline 7, a mixer 8, a distillation tower 9, a second reverse osmosis unit 10, a reduction reaction tank 11, and a bromine storage tank 12; the ozone oxidation tower 6 is provided with a middle water inlet, a lower ozone gas inlet, and a lower drain outlet; the distillation tower 9 is provided with a middle and upper feed inlet, a top collection outlet, a bottom discharge outlet, and a middle feed inlet.

[0052] The outlet of the bromine washing wastewater storage tank 1 is connected to the inlet of the raw water tank of the nanofiltration unit 2, the nanofiltration product water outlet of the nanofiltration unit 2 is connected to the inlet of the raw water tank of the first reverse osmosis unit 3, the concentrate outlet of the first reverse osmosis unit 3 is connected to the inlet of the feed pump of the MVR evaporator unit 4, and the mother liquor outlet of the MVR evaporator unit 4 is connected to the inlet of the bromine-rich storage tank 5. The outlet pipeline of the bromine-rich storage tank 5 is connected to the acid addition pipeline 7 and then connected together to the middle water inlet of the ozone oxidation tower 6 through the mixer 8. The lower drain outlet of the ozone oxidation tower 6 is connected to the middle and upper feed inlet of the distillation tower 9. The top collection port of the distillation tower 9 is connected to the inlet of the bromine storage tank 12. The bottom discharge port of the distillation column 9 is connected to two pipelines. One pipeline is connected to the raw water tank inlet of the second reverse osmosis unit 10. The concentrate outlet of the second reverse osmosis unit 10 is connected to the middle feed port of the distillation column 9 through the reduction reaction tank 11.

[0053] The ozone generator is connected to the lower ozone inlet of the ozone oxidation tower 6.

[0054] The other pipeline connecting the nanofiltration concentrate outlet of the nanofiltration device 2 and the bottom discharge port of the distillation column 9 is connected to the waste liquid pool.

[0055] The product water outlet of the first reverse osmosis unit 3, the product water outlet of the second reverse osmosis unit 10, and the secondary steam condensate outlet of the MVR evaporator unit 4 are all connected to the clear water storage tank 13; a shell-and-tube condenser is provided at the top of the distillation column 9; the clear water storage tank 13 is connected to the condenser tube of the shell-and-tube condenser at the top of the distillation column.

[0056] The bottom ring of the distillation column 9 is provided with a heat insulation jacket, which has a heat source inlet and a heat source outlet; the non-condensable gas outlet of the MVR evaporator is connected to the heat source inlet of the heat insulation jacket.

[0057] Example 2

[0058] This embodiment provides a method for bromine extraction from brominated flame retardant washing wastewater. The method uses the system described in Example 1. The brominated flame retardant washing wastewater is 1000L of washing wastewater from the production of tetrabromobisphenol A, and its water quality conditions include: bromide ion concentration of 805mg / L, sulfate concentration of 4150mg / L, and COD concentration of 2760mg / L. The method includes the following steps: S1: The washing wastewater from the production of tetrabromobisphenol A is fed from the bromine washing wastewater storage tank 1 into the nanofiltration unit 2. After nanofiltration treatment, nanofiltration concentrate 2.1 and sodium bromide-containing nanofiltration permeate 2.2 are obtained. The sodium bromide-containing nanofiltration permeate 2.2 is fed into the first reverse osmosis unit 3. After first reverse osmosis treatment, first reverse osmosis permeate 3.1 and sodium bromide-containing reverse osmosis concentrate 3.2 (bromine ion concentration reaches 7500 mg / L) are obtained. The sodium bromide-containing reverse osmosis concentrate 3.2 is fed into the MVR evaporator unit 4. After evaporation and concentration treatment, non-condensable gas (not shown), secondary steam condensate 4.1, and sodium bromide-containing mother liquor 4.2 are obtained. The sodium bromide-containing mother liquor 4.2 is fed into the bromine-rich storage tank 5. in: The nanofiltration recovery rate of the nanofiltration treatment was 50%. The reverse osmosis recovery rate of the first reverse osmosis treatment is 80%; The evaporation temperature of the evaporation and concentration process is 95°C, and the concentration factor is approximately 10 times. The concentration of sodium bromide in the sodium bromide-containing mother liquor is 68.5 g / L.

[0059] S2: The sodium bromide mother liquor in the bromine-rich storage tank is mixed with acid and then fed into the ozone oxidation tower 6. After ozone oxidation treatment, a feed liquid containing elemental bromine and bromate is obtained. The feed liquid containing elemental bromine and bromate is fed into the distillation tower 9. After distillation treatment, bromine is obtained at the top of the distillation tower, and a residual liquid 9.1 containing bromate is obtained at the bottom of the distillation tower. in: The pH of the solution obtained by mixing sodium bromide mother liquor and acid in the bromine-rich storage tank is 2-4; The ozone concentration inside the ozone oxidation tower 6 is controlled at 100 mg / L; The temperature inside the ozone oxidation tower 6 is ≤25℃, and the ozone oxidation treatment time is 30min; The temperature of the liquid in the distillation column 9 is 60-70℃.

[0060] S3: The bromine (weighing 6.05 kg) is stored in the bromine storage tank 12; a portion of the residual liquid 9.1 containing bromate is sent to the second reverse osmosis unit 10, and after second reverse osmosis treatment, second reverse osmosis permeate 10.1 and bromate-containing reverse osmosis concentrate 10.2 are obtained; the bromate-containing reverse osmosis concentrate 10.2 is reduced and then sent to the distillation column 9 for distillation treatment; wherein: After steps S1-S3, the bromine extraction rate at the top of distillation column 9 in this embodiment is 88.3%. The reverse osmosis recovery rate of the second reverse osmosis treatment is 45-55%; The reducing agent used in the reduction process is sulfite.

[0061] This embodiment also includes: The nanofiltration concentrate 2.1 and the remaining portion of the bromate-containing residual liquid are discharged into the waste liquid tank; The first reverse osmosis permeate 3.1, the second reverse osmosis permeate 10.1, and the secondary steam condensate 4.1 are discharged into the clear water storage tank 13. Then, the water in the clear water storage tank 13 is sent into the condenser tube of the shell-and-tube condenser at the top of the distillation column 9 as a cold source for condensing bromine vapor, thereby obtaining bromine at the top of the distillation column. The non-condensable gas is fed into the insulation jacket at the bottom of the distillation column 9 to exchange heat with the liquid in the distillation column as a heat source.

[0062] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A system for removing bromine from bromine-containing flame retardant wash wastewater, characterized by comprising: The system comprises a removal of impurity bromine concentration unit and a bromine extraction unit; The removal of impurity bromine concentration unit comprises a washing of bromine wastewater storage tank, a nanofiltration device, a first reverse osmosis device and an MVR evaporator device; The bromine extraction unit comprises a rich bromine storage tank, an ozone oxidation tower, an acid adding pipeline, a mixer, a distillation column, a second reverse osmosis device, a reduction reaction tank and a bromine storage tank; the ozone oxidation tower is provided with a middle water inlet, a lower ozone gas inlet and a lower water outlet; the distillation column is provided with a middle upper feed inlet, a top recovery inlet, a bottom discharge outlet and a middle feed inlet; The outlet of the washing of bromine wastewater storage tank is connected with the raw water tank water inlet of the nanofiltration device; the nanofiltration water outlet of the nanofiltration device is connected with the raw water tank water inlet of the first reverse osmosis device; the concentrated water outlet of the first reverse osmosis device is connected with the feed pump inlet of the MVR evaporator device; the mother liquor outlet of the MVR evaporator device is connected with the inlet of the rich bromine storage tank; The outlet of the rich bromine storage tank is connected with the acid adding pipeline; the acid adding pipeline and the ozone oxidation tower middle water inlet are connected through the mixer; the lower water outlet of the ozone oxidation tower is connected with the middle upper feed inlet of the distillation column; the top recovery inlet of the distillation column is connected with the inlet of the bromine storage tank; The bottom discharge outlet of the distillation column is connected with two pipelines; one of the pipelines is connected with the raw water tank water inlet of the second reverse osmosis device; the concentrated water outlet of the second reverse osmosis device is connected with the middle feed inlet of the distillation column through the reduction reaction tank.

2. The bromine extraction system for bromine flame retardant washing wastewater according to claim 1, wherein, The system further comprises a waste liquid pool and a clean water storage tank; The nanofiltration concentrated water outlet of the nanofiltration device and the other pipeline connected with the bottom discharge outlet of the distillation column are both connected with the waste liquid pool; The water outlet of the first reverse osmosis device, the water outlet of the second reverse osmosis device and the secondary steam condensate water outlet of the MVR evaporator device are all connected with the clean water storage tank.

3. The bromine extraction system for bromine flame retardant washing wastewater according to claim 2, wherein, The distillation column is provided with a shell and tube condenser at the top; the clean water storage tank is connected with the condensing pipe of the shell and tube condenser of the distillation column top.

4. The bromine extraction system for bromine flame retardant washing wastewater according to claim 1, wherein, The system further comprises an ozone generator; the ozone generator is connected with the lower ozone gas inlet of the ozone oxidation tower; The ozone oxidation tower is further provided with a middle reflux inlet; the lower water outlet of the ozone oxidation tower is divided into two; one is connected with the middle upper feed inlet of the distillation column; the other is connected with the middle reflux inlet of the ozone oxidation tower.

5. The bromine extraction system for bromine flame retardant washing wastewater according to claim 1, wherein, The distillation column is provided with a heat preservation jacket at the bottom; the heat preservation jacket is provided with a heat source inlet and a heat source outlet; The non-condensable gas outlet of the MVR evaporator device is connected with the heat source inlet of the heat preservation jacket.

6. A method for removing bromine from bromine-containing flame retardant washing wastewater, characterized by comprising the steps of: The method adopts the system of any one of claims 1-5, comprising the following steps: S1: the washing wastewater of producing tetrabromobisphenol A is sent from the washing of bromine wastewater storage tank to the nanofiltration device, and is treated by nanofiltration to obtain nanofiltration concentrated water and sodium bromide containing nanofiltration water; the sodium bromide containing nanofiltration water is sent to the first reverse osmosis device, and is treated by first reverse osmosis to obtain first reverse osmosis water and sodium bromide containing reverse osmosis concentrated water; the sodium bromide containing reverse osmosis concentrated water is sent to the MVR evaporator device, and is treated by evaporation concentration to obtain non-condensable gas, secondary steam condensate water and sodium bromide containing mother liquor; the sodium bromide containing mother liquor is sent to the rich bromine storage tank; S2: the bromine-containing sodium mother liquor in the bromine-rich storage tank is mixed with acid and then sent to the ozone oxidation tower for ozone oxidation treatment to obtain a solution containing elemental bromine and bromate; the solution containing elemental bromine and bromate is sent to the distillation tower for distillation treatment, and bromine is obtained at the top of the distillation tower, and residual liquid containing bromate is obtained at the bottom of the distillation tower; S3: the bromine is sent to the bromine storage tank for storage; part of the residual liquid containing bromate is sent to the second reverse osmosis device for second reverse osmosis treatment to obtain second reverse osmosis produced water and reverse osmosis concentrated water containing bromate; the reverse osmosis concentrated water containing bromate is sent to the distillation tower for the distillation treatment after reduction treatment.

7. The method of claim 6, wherein the bromine recovery method of bromine- based flame retardant scrubbing wastewater is characterized by, The method further comprises: the nanofiltration concentrated water and the remaining part of the residual liquid containing bromate are discharged to a waste liquid pool; the first reverse osmosis produced water, the second reverse osmosis produced water and the secondary steam condensed water are discharged to a clean water storage tank, and then the water in the clean water storage tank is sent to the condensing pipe of the shell-and-tube condenser at the top of the distillation tower as a cold source for condensing bromine vapor, and thus bromine is obtained at the top of the distillation tower; the non-condensable gas is sent to the heat preservation jacket arranged at the bottom of the distillation tower as a heat source to exchange heat with the solution in the distillation tower.

8. The method for extracting bromine from bromine-based flame retardant washing wastewater according to claim 6, wherein the water quality conditions of the washing wastewater for producing tetrabromobisphenol A include: a bromide ion concentration of 800-1000 mg / L, a sulfate ion concentration of 3000-5000 mg / L, and a COD concentration of 2000-3000 mg / L; the nanofiltration recovery rate of the nanofiltration treatment is 50-70%; the reverse osmosis recovery rate of the first reverse osmosis treatment is 75-80%; the evaporation temperature of the evaporation concentration treatment is 90-95°C, and the concentration multiple is 5-10 times; the concentration of sodium bromide in the sodium bromide-containing mother liquor is 50-100 g / L.

9. The method for extracting bromine from bromine-based flame retardant washing wastewater according to claim 6, wherein the pH of the solution obtained by mixing the sodium bromide-containing mother liquor in the bromine-rich storage tank with acid is 2-4; The ozone concentration in the ozone oxidation tower is controlled at 80-100 mg / L, the ozone gas inlet amount is 100-150 Nm 3 / h; the temperature in the ozone oxidation tower is ≤25℃; the temperature of the solution in the distillation tower is 60-70°C; and the bromine extraction rate at the top of the distillation tower is ≥80%.

10. The method for extracting bromine from bromine-based flame retardant washing wastewater according to claim 6, wherein the reverse osmosis recovery rate of the second reverse osmosis treatment is 45-55%; the reducing agent used in the reduction treatment is sulfite.

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