A system and method for recovering bromine salts from a bromine-containing wastewater of an rto scrubbing tower

Abstract

The present application relates to the technical field of industrial wastewater treatment and resource recovery, and discloses a system and method for recovering bromine salt from bromine-containing wastewater of an RTO washing tower, wherein the RTO washing tower body is connected with a pH adjusting module, an oxidation stripping module, an absorption module and an evaporation crystallization module in sequence; the present application combines the processes of acidic condition oxidation and two-stage countercurrent stripping absorption, thereby improving the total recovery rate of bromine ions in the wastewater, improving the purity of the bromine salt product obtained by evaporation crystallization, meeting the industrial-grade bromine salt product standard, and being directly reused in the synthesis of bromine-based chemicals, the production of printing and dyeing auxiliaries and other scenes, thereby greatly improving the utilization rate of valuable resources; without adding a large amount of flocculants, reducing agents and other reagents, compared with the reverse osmosis / evaporation desalination process of conventional high-salinity wastewater, the unit wastewater treatment cost is reduced, the income generated by bromine salt recovery can cover part of the system operation cost, and the wastewater treatment burden of enterprises is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment and resource recovery technology, specifically to a system and method for recovering bromide salts from bromine-containing wastewater in an RTO scrubbing tower. Background Technology

[0002] Regenerative thermal oxidizers (RTOs) are currently the mainstream equipment for treating high-concentration organic waste gases from industries such as chemical, printing and dyeing, and electronics. For organic waste gas treatment scenarios containing bromine-containing components such as bromine-based flame retardants, bromine-substituted hydrocarbons, and hydrogen bromide, during the high-temperature combustion process of the RTO, bromine is converted into gaseous hydrogen bromide and enters the subsequent alkaline scrubbing tower with the flue gas. After neutralization by alkaline solutions such as sodium hydroxide / potassium hydroxide, bromine salts such as sodium bromide / potassium bromide are generated and enter the scrubbing wastewater, forming bromine-containing wastewater.

[0003] The current industry standard for treating bromine-containing wastewater involves first adding reducing agents such as sodium sulfite and sodium thiosulfate to eliminate residual oxidizing substances in the wastewater, and then directly discharging it into the plant's integrated wastewater treatment station for mixing with other wastewater for biological treatment. Since bromine salts are important chemical raw materials, the lack of resource recovery leads to resource waste. Furthermore, the high salinity of bromine-containing wastewater inhibits microbial activity within the biological treatment system, significantly reducing treatment efficiency and potentially causing system failure, which severely impacts subsequent wastewater treatment systems. Enterprises must invest heavily in diluting or special desalination of the high-salinity wastewater. Moreover, many regions in China have included total wastewater salinity in their emission control indicators, and conventional treatment methods cannot meet low-salinity emission requirements, resulting in poor compliance and hindering normal production and operation. Therefore, this paper proposes a system and method for recovering bromine salts from bromine-containing wastewater in an RTO scrubbing tower. Summary of the Invention

[0004] The purpose of this invention is to provide a system and method for recovering bromide salts from bromine-containing wastewater in an RTO scrubbing tower. This addresses the problems mentioned in the background art, such as the waste of resources due to the lack of resource recovery and utilization of bromide salts, which are important chemical raw materials; the high salinity of bromine-containing wastewater inhibiting the activity of microorganisms in the biochemical system, significantly reducing biochemical treatment efficiency, and in severe cases, causing the biochemical system to shut down, which has a significant impact on subsequent wastewater treatment systems. Enterprises need to invest a lot of extra costs in diluting high-salinity wastewater or special desalination treatment; moreover, many regions in China have now included total salinity of wastewater in their emission control indicators, and conventional treatment methods cannot meet the requirements for low-salinity emissions, resulting in poor emission compliance and hindering the normal production and operation of enterprises.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a system for recovering bromine salts from bromine-containing wastewater in an RTO scrubbing tower, comprising... The RTO scrubbing tower body and the pH adjustment module, oxidation stripping module, absorption module and evaporation crystallization module connected in sequence; The inlet of the pH adjustment module is connected to the wastewater outlet of the RTO scrubbing tower body. The pH adjustment module is equipped with a pH detection unit and an acid dosing unit. The oxidation stripping module includes a stripping tower, an oxidant dosing unit, and an aeration unit. The inlet of the stripping tower is connected to the outlet of the pH adjustment module, the outlet of the oxidant dosing unit is connected to the lower reaction zone of the stripping tower, and the outlet of the aeration unit is located at the bottom of the stripping tower. The absorption module includes a primary absorption tower and a secondary absorption tower. The top outlet of the stripping tower is connected to the lower inlet of the primary absorption tower, and the top outlet of the primary absorption tower is connected to the lower inlet of the secondary absorption tower. Both the primary and secondary absorption towers are equipped with alkali spraying units. The inlet of the evaporation crystallization module is connected to the outlet of the primary absorption tower and the secondary absorption tower, respectively, and the solid phase outlet of the evaporation crystallization module is the outlet of the bromine salt product.

[0006] Preferably, the pH adjustment module further includes a stirring assembly for stirring the acid solution being added, wherein the acid added by the acid addition unit is industrial hydrochloric acid or industrial sulfuric acid with a mass fraction of 30%.

[0007] Preferably, the stirring assembly includes a fixed frame mounted on the ground, a dosing tank, and a drive motor. The dosing tank is mounted on the fixed frame, and the drive motor is mounted on the top of the dosing tank via a mounting plate. The output shaft of the drive motor is fixedly connected to a stirring shaft, and the stirring shaft is inserted into the dosing tank through a coaxial connecting hole on the mounting plate and the dosing tank. A fixed base is fixedly connected to the outer end of the stirring shaft, and symmetrically arranged mounting grooves are opened on the outer side of the fixed base. A connecting column is hinged inside the mounting groove, and a stirring blade is provided at the end of the connecting column. An adjustment assembly is provided on the outer side of the stirring shaft.

[0008] Preferably, the adjusting assembly includes an internal threaded seat and a rotating seat. The internal threaded seat is threadedly connected to the outside of the stirring shaft. The rotating seat is rotatably connected to the bottom of the internal threaded seat and sleeved on the outside of the stirring shaft. Symmetrically arranged connecting rods are hinged to the outside of the rotating seat. One end of the connecting rod is hinged to the outside of the connecting column. An insertion hole is provided on the outside of the internal threaded seat. A telescopic spring is sleeved on the outside of the stirring shaft between the fixed seat and the rotating seat. The telescopic spring is in a compressed state.

[0009] Preferably, the oxidant added by the oxidant addition unit of the oxidation stripping module is any one of chlorine, hydrogen peroxide or sodium hypochlorite, and the amount of oxidant added is 1.05-1.2 times the molar amount of bromide ions in the wastewater.

[0010] Preferably, the inside of the stripping tower is further provided with a multi-layer polypropylene Pall ring packing layer below the water inlet, and the air-to-water ratio of the aeration unit is controlled at (150-300):1.

[0011] Preferably, the alkaline solution sprayed by the alkaline spraying unit of the primary and secondary absorption towers is a sodium hydroxide solution or potassium hydroxide solution with a mass fraction of 10%-20%, the pH of the circulating absorbent in the primary absorption tower is 7.0-10.0, and the pH of the circulating absorbent in the secondary absorption tower is above 12.0.

[0012] Preferably, the top outlet of the secondary absorption tower is also connected to a tail gas treatment unit, which is an activated carbon adsorption tower or a reducing alkaline spray tower.

[0013] Preferably, the evaporation and crystallization module uses an MVR evaporator, with an evaporation concentration ratio of 5-8 times and a cooling and crystallization temperature controlled at 10-25℃.

[0014] A method for recovering bromide salts from bromine-containing wastewater in an RTO scrubbing tower includes the following steps: S1, pH adjustment: The bromine-containing wastewater discharged from the RTO scrubbing tower is passed into the pH adjustment module, and acid is added to adjust the pH to 2.0-4.0; S2. Oxidative stripping: The pH-adjusted wastewater is fed into the oxidative stripping module. An oxidant is added to oxidize the bromide ions in the wastewater into elemental bromine. The residence time of the oxidation reaction is 30-60 minutes, and the reaction temperature is controlled at 25-40℃. At the same time, aeration is used to strip the elemental bromine into bromine vapor and discharge it. S3. Alkali absorption: Bromine vapor is sequentially introduced into the primary absorption tower and the secondary absorption tower, where it reacts countercurrently with the alkali solution to form a bromine salt solution. The countercurrent contact time between the bromine vapor and the alkali solution is not less than 2 seconds, and the total absorption efficiency of elemental bromine is not less than 99.5%. S4. Evaporation and crystallization: The bromine salt solution discharged from the primary and secondary absorption towers is passed into the evaporation and crystallization module. After evaporation and concentration, it is cooled and crystallized, and then centrifuged to obtain the bromine salt product.

[0015] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects: 1. This invention improves the total recovery rate of bromide ions in wastewater by combining acidic oxidation with two-stage countercurrent stripping absorption, thereby increasing the purity of the bromide salt product obtained by evaporation and crystallization. The bromide salt product meets the standards for industrial-grade bromide salt products and can be directly reused in the synthesis of bromine-based chemicals, the production of dyeing and printing auxiliaries, and other scenarios, thus significantly improving the utilization rate of valuable resources.

[0016] 2. This invention does not require the addition of large amounts of flocculants, reducing agents, and other reagents. Compared with conventional reverse osmosis / evaporation desalination processes for high-salt wastewater, it reduces the unit wastewater treatment cost. At the same time, the revenue generated from bromine salt recovery can cover part of the system operating costs, significantly reducing the wastewater treatment burden for enterprises.

[0017] 3. This invention can reduce the residual bromide ions in the treated wastewater and lower the total salinity, allowing it to be directly discharged into the plant's integrated wastewater treatment station for subsequent biochemical treatment without inhibiting microbial activity. It can also meet the total salinity discharge limits for wastewater in all regions of China without the need for an additional desalination unit. Furthermore, the system adopts a modular design with a wide parameter control range, making it adaptable to different RTO bromide-containing wastewater treatment scenarios.

[0018] 4. This invention drives the stirring shaft to rotate via a drive motor, which in turn drives the stirring blades to rotate via a fixed seat. This ensures that the pH adjuster is quickly and evenly dispersed, avoiding local over-concentration or stratification. Furthermore, by rotating the internal threaded seat, the stirring blades can be flipped and folded under the fixed seat via the rotating seat and connecting rod to push or pull the connecting column. This facilitates the removal and cleaning of the stirring blades from the dosing tank and meets the needs of dosing tanks with smaller inner diameters. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the recycling method of the present invention; Figure 2 This is a schematic diagram of the dosing tank structure of the present invention; Figure 3 This is a schematic diagram of the internal thread seat structure of the present invention; Figure 4 This is a schematic diagram of the fixing base structure of the present invention; Figure 5 This is a schematic diagram of the internal structure of the dosing tank of the present invention; Figure 6 This is a schematic diagram of the stirring shaft structure of the present invention.

[0021] Explanation of reference numerals in the attached drawings: 1. Fixing frame; 2. Dosing tank; 3. Metering pump; 4. Pipeline; 5. Connector; 6. Mesh cover; 7. Drive motor; 8. Stirring shaft; 9. Fixing base; 10. Mounting groove; 11. Connecting column; 12. Stirring blade; 13. Internal threaded seat; 14. Rotary seat; 15. Connecting rod; 16. Insertion hole; 17. Telescopic spring; 18. Connecting cover; 19. Valve. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that the structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which this application can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size should still fall within the scope of the technical content disclosed in this application, provided that they do not affect the effects and purposes that this application can produce.

[0024] Example 1 This invention provides a technical solution: a bromide recovery system for bromide-containing wastewater from an RTO scrubbing tower, comprising an RTO scrubbing tower body and a pH adjustment module, an oxidation stripping module, an absorption module, and an evaporation crystallization module connected in sequence; The inlet of the pH adjustment module is connected to the wastewater outlet of the RTO scrubbing tower body. The pH adjustment module is equipped with a pH detection unit and an acid dosing unit. The pH detection unit and the acid dosing unit are linked for control to reduce manual intervention. The pH adjustment module also includes a stirring component, which is used to stir the acid solution being added. The acid added by the acid dosing unit is industrial hydrochloric acid with a mass fraction of 30%. The oxidation stripping module includes a stripping tower, an oxidant dosing unit, and an aeration unit. The inlet of the stripping tower is connected to the outlet of the pH adjustment module, the outlet of the oxidant dosing unit is connected to the lower reaction zone of the stripping tower, and the outlet of the aeration unit is located at the bottom of the stripping tower. The oxidant added by the oxidant dosing unit of the oxidation stripping module is hydrogen peroxide, and the dosage of the oxidant is 1.1 times the molar amount of bromide ions in the wastewater. The dosage of the oxidant is set according to the stoichiometric ratio to avoid excessive oxidant residue or side reactions, ensuring high system safety. Inside the stripping tower, below the inlet, there is also a multi-layer polypropylene Pall ring packing layer. The polypropylene Pall ring packing layer enhances gas-liquid mass transfer and improves stripping efficiency. The gas-water ratio of the aeration unit is controlled at 200:1. Through the combination of acidic oxidation and two-stage countercurrent stripping absorption, the total recovery rate of bromide ions in the wastewater is improved, and the purity of the bromide salt product obtained by evaporation and crystallization is increased, meeting the standards for industrial-grade bromide salt products and significantly improving the utilization rate of valuable resources. The absorption module includes a primary absorption tower and a secondary absorption tower. The pH is controlled in stages through the two absorption towers to ensure complete absorption of bromine gas and prevent escape. The top outlet of the stripping tower is connected to the lower inlet of the primary absorption tower, and the top outlet of the primary absorption tower is connected to the lower inlet of the secondary absorption tower. Both the primary and secondary absorption towers are equipped with alkaline spray units. The alkaline solution sprayed by the alkaline spray units of the primary and secondary absorption towers is a 15% sodium hydroxide solution. The pH of the circulating absorbent in the primary absorption tower is 8.5, and the pH of the circulating absorbent in the secondary absorption tower is 13. The top outlet of the secondary absorption tower is also connected to a tail gas treatment unit, which is either an activated carbon adsorption tower or a reducing alkaline spray tower. The tail gas is discharged after being treated by activated carbon or reducing alkaline spray and meets the emission standards without secondary pollution. The inlet of the evaporation crystallization module is connected to the outlet of the primary and secondary absorption towers respectively. The solutions from the primary and secondary absorption towers can be collected into an intermediate storage tank and then pumped into the evaporation crystallization module. The solid phase outlet of the evaporation crystallization module is the bromide product outlet. The evaporation crystallization module adopts an MVR evaporator. The MVR evaporator uses mechanically compressed steam technology, which has high energy efficiency, controllable crystallization temperature, and lower energy consumption than traditional evaporators. The evaporation concentration ratio is 6 times, and the cooling crystallization temperature is controlled at 15℃.

[0025] Through a continuous process of pH adjustment, oxidative stripping, two-stage alkaline absorption, and evaporation crystallization, bromide ions in wastewater can be efficiently converted into bromide products, improving the recovery rate and reducing resource waste.

[0026] Example 2 Please see Figure 2-6 Unlike Example 1, the pH adjustment module also includes a stirring assembly, which is used to stir the acid solution being added. The acid added by the acid addition unit is industrial hydrochloric acid with a mass fraction of 30%.

[0027] By setting up a stirring assembly, the pH adjuster can be rapidly and evenly dispersed, avoiding local over-concentration or stratification. The stirring assembly includes a fixed frame 1 mounted on the ground, a dosing tank 2, and a drive motor 7. The dosing tank 2 is mounted on the fixed frame 1, and the top of the dosing tank 2 can be flat to facilitate the folding operation of the stirring blades 12. The drive motor 7 is mounted on the top of the dosing tank 2 via a mounting plate. The output shaft of the drive motor 7 is fixedly connected to a stirring shaft 8, and the stirring shaft 8 is inserted into the dosing tank 2 through a coaxial connecting hole on the mounting plate and the dosing tank 2. A fixed base 9 is fixedly connected to the outer end of the stirring shaft 8. The outer side of the fixed base 9 has symmetrically arranged mounting grooves 10. A connecting post 11 is hinged inside the mounting groove 10, and a stirring blade 12 is provided at the end of the connecting post 11. Figure 2 and attached Figure 5 As shown, when stirring the solution, the drive motor 7 is started by controlling the drive motor 7 to rotate. The output shaft of the drive motor 7 drives the stirring shaft 8 to rotate, and the four stirring blades 12 rotate inside the dosing tank 2 via the fixed seat 9. This can stir the solution inside the dosing tank 2, prevent the solution from having local concentration differences or stratification, and provide a guarantee for the adjustment of the pH value of the wastewater. By setting an adjustment component, the angle of the stirring blade 12 can be adjusted, making it convenient to remove the stirring blade 12 from the dosing tank 2 for cleaning, while also meeting the usage requirements of the small inner diameter dosing tank 2. An adjustment component is set on the outside of the stirring shaft 8. The adjustment component includes an internal thread seat 13 and a rotating seat 14. The internal thread seat 13 is threadedly connected to the outside of the stirring shaft 8. The rotating seat 14 is rotatably connected to the bottom of the internal thread seat 13 and sleeved on the outside of the stirring shaft 8. Symmetrically arranged connecting rods 15 are hinged to the outside of the rotating seat 14. One end of the connecting rod 15 is hinged to the outside of the connecting column 11. The hinge axis between the connecting rod 15 and the connecting column 11 is not on the same horizontal line as the hinge axis between the connecting column 11 and the mounting groove 10, so as to avoid interference with the folding of the connecting rod 15. An insertion hole 16 is opened on the outside of the internal thread seat 13, as shown in the attached figure. Figure 3As shown, when the stirring blade 12 needs to be removed from the dosing tank 2 for cleaning, the drive motor 7 is disassembled, and the stirring blade 12 is moved into the connecting hole of the dosing tank 2 via the stirring shaft 8. At this time, the internal thread seat 13 can be rotated in the reverse direction with the help of a tool. For fixing the internal thread seat 13, a bolt can be installed on the internal thread seat 13, and the position is fixed by the end of the bolt contacting the outside of the stirring shaft 8. The internal thread seat 13 moves downward on the outside of the stirring shaft 8, so that the internal thread seat 13 pushes the stirring blade 12 on the connecting column 11 to move via the connecting rod 15. One end of the connecting column 11 is in the mounting groove 10. The internal rotation of the stirring shaft 8 causes the stirring blades 12 to flip, and the four stirring blades 12 are folded under the fixed seat 9, so that the four stirring blades 12 can be easily removed from the dosing tank 2 and easily cleaned. A telescopic spring 17 is sleeved on the outside of the stirring shaft 8 between the fixed seat 9 and the rotating seat 14. The telescopic spring 17 can be made of corrosion-resistant material and needs to be maintained and replaced after long-term use. The telescopic spring 17 is in a compressed state, and the telescopic spring 17 provides axial preload to the internal thread seat 13 and the rotating seat 14, which can prevent the internal thread seat 13 from rotating due to vibration. When it is necessary to install the stirring blades 12 in the dosing tank 2 with a smaller inner diameter, first place the four stirring blades 12 inside the dosing tank 2, use a tool to rotate the internal thread seat 13 in the forward direction, the internal thread seat 13 moves upward and pulls one end of the connecting column 11 through the connecting rod 15, thereby unfolding the four stirring blades 12 in the dosing tank 2. When the stirring blades 12 are unfolded to a suitable angle, the adjustment of the internal thread seat 13 can be stopped, and then the drive motor 7 can be installed on the dosing tank 2.

[0028] The acid dosing unit includes a metering pump 3 installed on the dosing tank 2. The metering pump 3 is used to transport the dosing solution. A pipe 4 is installed at the inlet end of the metering pump 3. The pipe 4 is located inside the dosing tank 2. A connector 5 is installed at one end of the pipe 4. A mesh cover 6 is installed on the connector 5. The mesh cover 6 can filter the added solution. It can be made of corrosion-resistant material. A connecting cover 18 is installed on the top of the dosing tank 2. An air inlet check valve is set on the connecting cover 18. The connecting cover 18 is used to close the liquid filling port of the dosing tank 2 and facilitates the cleaning of the inside of the dosing tank 2. A valve 19 is set at the lower outer side of the dosing tank 2. When cleaning the dosing tank 2, adjusting the valve 19 can discharge the waste liquid in the dosing tank 2.

[0029] Example 3 Please see Figure 1 Unlike Examples 1 and 2, a method for recovering bromide salts from bromine-containing wastewater in an RTO scrubbing tower includes the following steps: S1, pH adjustment: The bromine-containing wastewater discharged from the RTO scrubbing tower is passed into the pH adjustment module, and industrial sulfuric acid is added to adjust the pH to 3.0; S2. Oxidative stripping: The pH-adjusted wastewater is fed into the oxidative stripping module, and sodium hypochlorite is added as an oxidant at a dosage of 1.2 times the molar amount of bromide ions in the wastewater. The bromide ions in the wastewater are oxidized to elemental bromine. The residence time of the oxidation reaction is 45 minutes, and the reaction temperature is controlled at 30°C. At the same time, aeration is used to strip the elemental bromine into bromine vapor and discharge it. The aeration gas-water ratio is controlled at 250:1. S3. Alkali absorption: Bromine vapor is sequentially passed through a primary absorption tower and a secondary absorption tower, where it reacts countercurrently with the alkali solution to form a bromine salt solution. The alkali solution in the primary absorption tower is a 20% potassium hydroxide solution, and the pH of the circulating absorbent is controlled at 9.0. The alkali solution in the secondary absorption tower is a 10% sodium hydroxide solution, and the pH of the circulating absorbent is controlled at 13.0. The countercurrent contact time between the bromine vapor and the alkali solution is 3 seconds, and the total absorption efficiency of elemental bromine is not less than 99.5%. S4. Evaporation and crystallization: The bromide solution discharged from the primary and secondary absorption towers is passed into the evaporation and crystallization module. An MVR evaporator is used to evaporate and concentrate the solution by 5 times. The cooling and crystallization temperature is controlled at 20°C. The bromide product is obtained by centrifugation.

[0030] Example 4 Unlike Examples 1, 2 and 3, a system for recovering bromide salts from bromine-containing wastewater in an RTO scrubbing tower includes an RTO scrubbing tower body and a pH adjustment module, an oxidation stripping module, an absorption module and an evaporation crystallization module connected in sequence. The inlet of the pH adjustment module is connected to the wastewater outlet of the RTO scrubbing tower body. The pH adjustment module is equipped with a pH detection unit and an acid dosing unit. The pH adjustment module also includes a stirring component, which is used to stir the acid solution being added. The acid added by the acid dosing unit is 30% industrial sulfuric acid by mass. The oxidation stripping module includes a stripping tower, an oxidant dosing unit, and an aeration unit. The inlet of the stripping tower is connected to the outlet of the pH adjustment module. The outlet of the oxidant dosing unit is connected to the lower reaction zone of the stripping tower. The outlet of the aeration unit is located at the bottom of the stripping tower. The oxidant added by the oxidant dosing unit of the oxidation stripping module is chlorine gas. The dosage of the oxidant is 1.05 times the molar amount of bromide ions in the wastewater. The interior of the stripping tower is also equipped with a multi-layer polypropylene Pall ring packing layer below the inlet. The air-to-water ratio of the aeration unit is controlled at 150:1. The absorption module includes a primary absorption tower and a secondary absorption tower. The top outlet of the stripping tower is connected to the lower inlet of the primary absorption tower, and the top outlet of the primary absorption tower is connected to the lower inlet of the secondary absorption tower. Both the primary and secondary absorption towers are equipped with alkaline spraying units. The alkaline solution sprayed by the alkaline spraying units of the primary and secondary absorption towers is a 10% potassium hydroxide solution. The pH of the circulating absorbent in the primary absorption tower is 7, and the pH of the circulating absorbent in the secondary absorption tower is 13. The top outlet of the secondary absorption tower is also connected to a tail gas treatment unit, which is either an activated carbon adsorption tower or a reducing alkaline spraying tower. The inlet of the evaporation crystallization module is connected to the outlet of the primary absorption tower and the secondary absorption tower respectively. The solid phase outlet of the evaporation crystallization module is the outlet of the bromide product. The evaporation crystallization module adopts an MVR evaporator with an evaporation concentration ratio of 5 times and a cooling crystallization temperature control of 10℃.

[0031] In summary, this invention improves the total recovery rate of bromide ions in wastewater and enhances the purity of the bromide salt product obtained by evaporation and crystallization through a combination of acidic oxidation and two-stage countercurrent stripping absorption. This product meets the standards for industrial-grade bromide salt products and can be directly reused in scenarios such as the synthesis of bromine-based chemicals and the production of dyeing and printing auxiliaries, thus significantly improving the utilization rate of valuable resources. Compared with conventional reverse osmosis / evaporation desalination processes for high-salinity wastewater, this system eliminates the need for large amounts of flocculants and reducing agents, reducing unit wastewater treatment costs. Furthermore, the revenue generated from bromide recovery can cover part of the system's operating costs, significantly reducing the wastewater treatment burden for enterprises. It reduces the residual bromide ions in the treated wastewater and lowers the total salinity, allowing direct discharge into the plant's integrated wastewater treatment station for subsequent biochemical treatment without inhibiting microbial activity. It also meets the total salinity discharge limits for wastewater in all regions of China, eliminating the need for additional desalination units. The system's modular design and wide parameter control range make it adaptable to different RTO bromide-containing wastewater treatment scenarios. The drive motor 7 drives the stirring shaft 8 to rotate, which in turn drives the stirring blade 12 to rotate via the fixed seat 9. This ensures that the pH adjuster is quickly and evenly dispersed, avoiding local over-concentration or stratification. Furthermore, by rotating the internal thread seat 13, the connecting column 11 is pushed or pulled by the rotating seat 14 and connecting rod 15, allowing the stirring blade 12 to flip and fold under the fixed seat 9. This facilitates the removal and cleaning of the stirring blade 12 from the dosing tank 2 and also meets the usage requirements of the smaller inner diameter dosing tank 2.

[0032] Those skilled in the art will understand that the features described in the various embodiments and / or claims of the present invention can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, the features described in the various embodiments and / or claims of the present invention can be combined or combined in various ways without departing from the spirit and teachings of the present invention. All such combinations and / or combinations fall within the scope of the present invention.

Claims

1. A system for recovering bromide salts from bromine-containing wastewater in an RTO scrubbing tower, characterized in that, include The RTO scrubbing tower body and the pH adjustment module, oxidation stripping module, absorption module and evaporation crystallization module connected in sequence; The inlet of the pH adjustment module is connected to the wastewater outlet of the RTO scrubbing tower body. The pH adjustment module is equipped with a pH detection unit and an acid dosing unit. The oxidation stripping module includes a stripping tower, an oxidant dosing unit, and an aeration unit. The inlet of the stripping tower is connected to the outlet of the pH adjustment module, the outlet of the oxidant dosing unit is connected to the lower reaction zone of the stripping tower, and the outlet of the aeration unit is located at the bottom of the stripping tower. The absorption module includes a primary absorption tower and a secondary absorption tower. The top outlet of the stripping tower is connected to the lower inlet of the primary absorption tower, and the top outlet of the primary absorption tower is connected to the lower inlet of the secondary absorption tower. Both the primary and secondary absorption towers are equipped with alkali spraying units. The inlet of the evaporation crystallization module is connected to the outlet of the primary absorption tower and the secondary absorption tower, respectively, and the solid phase outlet of the evaporation crystallization module is the outlet of the bromine salt product.

2. The bromide salt recovery system for bromine-containing wastewater from an RTO scrubbing tower according to claim 1, characterized in that, The pH adjustment module also includes a stirring assembly, which is used to stir the acid solution being added. The acid added by the acid addition unit is industrial hydrochloric acid or industrial sulfuric acid with a mass fraction of 30%.

3. The bromide recovery system for bromide-containing wastewater from an RTO scrubbing tower according to claim 2, characterized in that, The stirring assembly includes a fixed frame (1) installed on the ground, a dosing tank (2) and a drive motor (7). The dosing tank (2) is installed on the fixed frame (1). The drive motor (7) is installed on the top of the dosing tank (2) via a mounting plate. The output shaft of the drive motor (7) is fixedly connected to a stirring shaft (8). The stirring shaft (8) is inserted into the dosing tank (2) through a coaxial connecting hole on the mounting plate and the dosing tank (2). A fixed seat (9) is fixedly connected to the outer end of the stirring shaft (8). A symmetrically arranged mounting groove (10) is provided on the outer side of the fixed seat (9). A connecting column (11) is hinged inside the mounting groove (10). A stirring blade (12) is provided at the end of the connecting column (11). An adjustment assembly is provided on the outer side of the stirring shaft (8).

4. The bromide salt recovery system for bromide-containing wastewater from an RTO scrubbing tower according to claim 3, characterized in that, The adjustment assembly includes an internal thread seat (13) and a rotating seat (14). The internal thread seat (13) is threaded to the outside of the stirring shaft (8). The rotating seat (14) is rotatably connected to the bottom of the internal thread seat (13) and sleeved on the outside of the stirring shaft (8). A symmetrically arranged connecting rod (15) is hinged to the outside of the rotating seat (14). One end of the connecting rod (15) is hinged to the outside of the connecting column (11). An insertion hole (16) is opened on the outside of the internal thread seat (13). A telescopic spring (17) is sleeved between the fixed seat (9) and the rotating seat (14) on the outside of the stirring shaft (8). The telescopic spring (17) is in a compressed state.

5. The bromide recovery system for bromide-containing wastewater from an RTO scrubbing tower according to claim 1, characterized in that, The oxidant added by the oxidant addition unit of the oxidation stripping module is any one of chlorine, hydrogen peroxide or sodium hypochlorite, and the amount of oxidant added is 1.05-1.2 times the molar amount of bromide ions in the wastewater.

6. The bromide salt recovery system for bromide-containing wastewater from an RTO scrubbing tower according to claim 1, characterized in that, The inside of the stripping tower, below the water inlet, is also equipped with a multi-layer polypropylene Pall ring packing layer, and the air-to-water ratio of the aeration unit is controlled at (150-300):

1.

7. The bromide recovery system for bromide-containing wastewater from an RTO scrubbing tower according to claim 1, characterized in that, The alkaline solution sprayed by the alkaline spraying unit of the primary and secondary absorption towers is a sodium hydroxide solution or potassium hydroxide solution with a mass fraction of 10%-20%. The pH of the circulating absorbent in the primary absorption tower is 7.0-10.0, and the pH of the circulating absorbent in the secondary absorption tower is above 12.

0.

8. The bromide salt recovery system for bromide-containing wastewater from an RTO scrubbing tower according to claim 1, characterized in that, The top outlet of the secondary absorption tower is also connected to a tail gas treatment unit, which is an activated carbon adsorption tower or a reducing alkaline solution spray tower.

9. A bromide salt recovery system for bromide-containing wastewater from an RTO scrubbing tower according to claim 1, characterized in that, The evaporation and crystallization module uses an MVR evaporator, with an evaporation and concentration ratio of 5-8 times, and the cooling and crystallization temperature is controlled at 10-25℃.

10. A method for recovering bromide salts from bromine-containing wastewater in an RTO scrubbing tower, characterized in that, Includes the following steps: S1, pH adjustment: The bromine-containing wastewater discharged from the RTO scrubbing tower is passed into the pH adjustment module, and acid is added to adjust the pH to 2.0-4.0; S2. Oxidative stripping: The pH-adjusted wastewater is fed into the oxidative stripping module. An oxidant is added to oxidize the bromide ions in the wastewater into elemental bromine. The residence time of the oxidation reaction is 30-60 minutes, and the reaction temperature is controlled at 25-40℃. At the same time, aeration is used to strip the elemental bromine into bromine vapor and discharge it. S3. Alkali absorption: Bromine vapor is sequentially introduced into the primary absorption tower and the secondary absorption tower, where it reacts countercurrently with the alkali solution to form a bromine salt solution. The countercurrent contact time between the bromine vapor and the alkali solution is not less than 2 seconds, and the total absorption efficiency of elemental bromine is not less than 99.5%. S4. Evaporation and crystallization: The bromine salt solution discharged from the primary and secondary absorption towers is passed into the evaporation and crystallization module. After evaporation and concentration, it is cooled and crystallized, and then centrifuged to obtain the bromine salt product.

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