Device and method for recycling and treating dilute brine produced from ion-exchange membrane caustic soda

Abstract

This invention discloses a device and method for recycling and treating desalinated brine produced by ion-exchange membrane caustic soda. The recycling and treatment device includes a dechlorination tower (4), an activated carbon adsorption column (5), a chlorine absorption tower (9), and an induced draft fan (10). The inlet of the dechlorination tower receives the desalinated brine produced by ion-exchange membrane caustic soda; the outlet of the dechlorination tower is connected to the inlet of the chlorine absorption tower; the outlet of the chlorine absorption tower is connected to the induced draft fan; the outlet of the dechlorination tower is connected to the inlet of the activated carbon adsorption column; and the desalinated brine output from the outlet of the activated carbon adsorption column is used as the treated finished desalinated brine. The recycling and treatment method includes: performing vacuum degassing treatment on the desalinated brine produced by the ion-exchange membrane caustic soda process; and performing activated carbon adsorption treatment on the desalinated brine after vacuum degassing treatment. The recycling and treatment device and method of this invention can realize the reuse of desalinated brine produced by ion-exchange membrane caustic soda, avoiding resource waste, saving costs, and preventing environmental pollution.

Description

Technical Field

[0001] This invention relates to an industrial water recycling technology, and more particularly to a device and method for recycling and treating refined brine produced from waste salt resources using ion-exchange membrane caustic soda to produce dilute brine. Background Technology

[0002] The production process of caustic soda using ion-exchange membranes generates a large amount of brine, which mainly consists of approximately 200 g / L of sodium chloride solution and 0.5–0.8 g / L of free chlorine.

[0003] As the main product of the ion-exchange membrane caustic soda process, the brine contains relatively few impurities besides free chlorine and other chlorides. From a resource perspective, it is entirely reusable. The best way to reuse it is to return it to the primary or secondary brine refining process (the preceding stage of the ion-exchange membrane caustic soda production process). However, if the brine is directly returned through pipelines, the free chlorine in it can easily corrode steel equipment and pipes, and it can also deactivate the chelating resin, resulting in losses.

[0004] Currently, there is no method for reusing refined brine produced from waste salt resources in the dilute brine produced by the ion-exchange membrane caustic soda process. As a result, the dilute brine cannot be reused. If the dilute brine that cannot be reused is discarded, it will not only be a waste of resources, but also cause environmental pollution. Summary of the Invention

[0005] The purpose of this invention is to provide a device and method for recycling and treating dilute brine produced by ion-exchange membrane caustic soda. This recycling and treatment device and method can realize the reuse of refined brine generated from waste salt resources for dilute brine produced by ion-exchange membrane caustic soda, thereby avoiding resource waste, saving costs, and also avoiding environmental pollution.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0007] A device for recycling and treating dilute brine produced by ion-exchange membrane caustic soda includes a dechlorination tower, an activated carbon adsorption column, a chlorine absorption tower, and an induced draft fan. The inlet of the dechlorination tower receives dilute brine produced by ion-exchange membrane caustic soda, the outlet of the dechlorination tower is connected to the inlet of the chlorine absorption tower, the outlet of the chlorine absorption tower is connected to the induced draft fan, the outlet of the dechlorination tower is connected to the inlet of the activated carbon adsorption column, and the dilute brine output from the outlet of the activated carbon adsorption column is used as the treated finished dilute brine.

[0008] Furthermore, the dechlorination tower is used to perform vacuum degassing treatment on the brine produced by the ion-exchange membrane caustic soda, and the activated carbon adsorption column is used to perform activated carbon adsorption treatment on the brine after vacuum degassing treatment.

[0009] Furthermore, the dechlorination tower has a compressed air inlet, which is connected to a compressed air supply source, and the compressed air inlet of the dechlorination tower can introduce compressed air provided by the compressed air supply source into the dechlorination tower.

[0010] Furthermore, a heating jacket is provided on the outside of the dechlorination tower.

[0011] Furthermore, the recycling and treatment device also includes a chlorinated brine storage tank, which is located before the pipeline that receives the brine at the inlet of the dechlorination tower. The brine produced by the ion-exchange membrane caustic soda process enters the inlet of the dechlorination tower from the outlet pipe of the chlorinated brine storage tank.

[0012] Furthermore, the recycling and processing device also includes a dechlorinated brine storage tank, which is installed on the pipeline from the outlet of the activated carbon adsorption column that outputs the treated brine. The treated brine is output from the outlet of the activated carbon adsorption column via the dechlorinated brine storage tank.

[0013] Furthermore, the recycling and processing device also includes a saline sampling bottle, which is installed on the pipeline that discharges saline from the ion-exchange membrane electrolyzer.

[0014] A method for recycling and treating desalinated brine produced by ion-exchange membrane caustic soda production, the method comprising: performing vacuum degassing on the desalinated brine produced by the ion-exchange membrane caustic soda process to remove free chlorine from the desalinated brine; and performing activated carbon adsorption on the desalinated brine after vacuum degassing to remove organic impurities from the desalinated brine.

[0015] Furthermore, the recycling method further includes: blowing compressed air into the brine produced by the ion-exchange membrane caustic soda process during vacuum degassing.

[0016] Furthermore, the recycling method further includes heating the brine produced by the ion-exchange membrane caustic soda process during vacuum degassing.

[0017] When using the recycling and treatment device and method of this invention to treat the brine produced from ion-exchange membrane caustic soda, a dechlorination tower is used to perform vacuum degassing on the brine to remove chlorine. Then, an activated carbon adsorption column is used to perform activated carbon adsorption treatment on the degassed brine to remove organic pollutants. The final treated brine has significantly reduced levels of free chlorine and organic pollutants, meeting the water standards for primary or secondary brine refining processes. This treated brine is then supplied to the primary or secondary brine refining process upstream of the ion-exchange membrane caustic soda process, thus achieving the reuse of the brine produced from ion-exchange membrane caustic soda. Compared to existing technologies that typically use chemical dosing to remove free chlorine from the brine, which requires the addition of sodium sulfite (which oxidizes sulfite to sulfate), and where barium chloride is still added to reduce sulfate levels during brine reuse, vacuum degassing reduces the need for subsequent sulfate removal processes. Activated carbon adsorption effectively removes organic pollutants from the brine. Blowing compressed air into the brine in the dechlorination tower and heating it can enhance the effectiveness of vacuum degassing. Activated carbon adsorption treatment can be activated or deactivated based on the actual total organic carbon (TOC) content in the brine; therefore, an bypass pipeline is installed to allow selection of the process route based on the actual TOC content in the brine.

[0018] The recycling and processing apparatus and method of the present invention have the following advantages over the prior art:

[0019] 1) It can realize the reuse of refined brine produced by waste salt resource utilization for the dilute brine produced by ion membrane caustic soda, thereby avoiding resource waste, saving costs, and also avoiding environmental pollution.

[0020] 2) It can reduce the subsequent sulfate removal process, save the amount of barium chloride used, reduce the amount of precipitated salt mud discharged, and at the same time ensure the removal effect of free chlorine in the brine.

[0021] 3) It can effectively remove organic pollutants from brine, enabling the ion-exchange membrane caustic soda process to adapt to refined brine obtained from waste salt containing a lot of organic matter generated from industries such as pharmaceuticals and pesticides after a series of resource-based treatments.

[0022] 4) Blowing compressed air into the brine in the dechlorination tower and heating it can improve the effect of vacuum degassing.

[0023] 5) Select the process route based on the actual content of total organic carbon in the brine, so as to achieve resource utilization and reduce costs. Attached Figure Description

[0024] Figure 1This is a process flow diagram of the ion-exchange membrane caustic soda desalinated water recycling and treatment device and method of the present invention.

[0025] In the diagram: 1-Ion membrane electrolyzer, 2-Dilute saline sampling bottle, 3-Chlorinated dilute saline storage tank, 4-Dechlorination tower, 5-Activated carbon adsorption column, 6-Dechlorinated dilute saline storage tank, 8-Compressed air supply source, 9-Chlorine absorption tower, 10-Exhaust fan. Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0027] See Figure 1 This embodiment provides a device for recycling and treating dilute brine produced by ion-exchange membrane caustic soda, which enables the reuse of dilute brine produced by ion-exchange membrane caustic soda.

[0028] The brine involved in this embodiment is the brine produced during the production process of the ion-exchange membrane caustic soda process. This brine is discharged from the "ion-exchange membrane electrolyzer 1 for implementing the ion-exchange membrane caustic soda process". In other words, the ion-exchange membrane electrolyzer 1 is the source of the brine received by the recycling and treatment device.

[0029] See Figure 1 The recycling and processing device of this embodiment includes: a chlorinated brine storage tank 3, a dechlorination tower 4, an activated carbon adsorption column 5, a dechlorinated brine storage tank 6, a chlorine absorption tower 9, and an induced draft fan 10.

[0030] The dechlorination tower 4 is a prior art device, essentially a "vacuum degassing device." This type of vacuum degassing device can perform "vacuum degassing treatment" on liquids, thereby removing free gases from the liquid to achieve the effect of "removing gases from the liquid." Like existing conventional vacuum degassing devices, the dechlorination tower 4 has three basic ports: a liquid inlet, a liquid outlet, and a gas outlet. The liquid inlet receives the liquid to be vacuum degassed, the gas outlet discharges the gases removed from the liquid, and the liquid outlet discharges the liquid after vacuum degassing. Furthermore, unlike conventional vacuum degassing devices, this embodiment of the dechlorination tower 4 also has a fourth port, called a "compressed air inlet," which is specifically used to introduce compressed air (described in detail later).

[0031] The chlorine absorption tower 9 is a prior art device capable of removing chlorine from gases. Specifically, the chlorine absorption tower 9 has four ports: two ports are designated as the inlet and outlet, respectively. The inlet receives the gas from which chlorine needs to be removed, and the outlet discharges the gas after chlorine removal. The other two ports are designated as the dilute alkali solution inlet and the waste liquid outlet. The chlorine absorption tower 9 contains a dilute alkali solution capable of absorbing chlorine. Gas entering the chlorine absorption tower 9 is circulated and sprayed by an external pump. The chlorine in the gas is absorbed by the dilute alkali solution and then discharged from the outlet, thus achieving the effect of "removing chlorine from the gas".

[0032] The activated carbon adsorption column 5 is a prior art activated carbon adsorption device with two ports, referred to as the inlet and outlet. The inlet is used to receive the liquid to be treated by activated carbon adsorption, and the outlet is used to discharge the liquid after activated carbon adsorption treatment. The activated carbon adsorption column 5 is equipped with activated carbon that can adsorb organic pollutants and remove odors. After the liquid entering the activated carbon adsorption column 5 is treated by activated carbon adsorption, the organic pollutant components in the liquid are adsorbed by the activated carbon, and the liquid is discharged from the outlet, thereby achieving the effect of "removing organic pollutant components from the liquid".

[0033] The chlorinated brine storage tank 3 and the dechlorinated brine storage tank 6 have essentially the same structure; both are tanks capable of holding and storing liquids. Each tank has two ports, serving as an inlet and an outlet. Liquid enters the tank through the inlet for storage and then exits through the outlet. In this embodiment, the chlorinated brine storage tank 3 and the dechlorinated brine storage tank 6 achieve a buffering effect.

[0034] The chlorinated brine storage tank 3 is located before the pipeline that receives the brine at the inlet of the dechlorination tower 4. The brine produced by the ion-exchange membrane caustic soda process enters the inlet of the dechlorination tower 4 from the outlet pipe of the chlorinated brine storage tank 3.

[0035] The inlet of the chlorinated brine storage tank 3 is connected to the brine outlet of the ion-exchange membrane electrolyzer 1 via a pipeline, and is used to receive the brine produced by the ion-exchange membrane caustic soda process discharged from the ion-exchange membrane electrolyzer 1. The outlet of the chlorinated brine storage tank 3 is connected to the inlet of the dechlorination tower 4 via a pipeline. That is to say, the inlet of the dechlorination tower 4 receives the brine produced by the ion-exchange membrane caustic soda process via the chlorinated brine storage tank 3. In the dechlorination tower 4, the dechlorination tower 4 performs vacuum degassing treatment on the brine to remove free chlorine from the brine.

[0036] The outlet of the dechlorination tower 4 is connected to the inlet of the activated carbon adsorption column 5 via a pipeline. In the activated carbon adsorption column 5, the desalinated water after vacuum degassing undergoes activated carbon adsorption treatment to remove organic impurities. The outlet of the activated carbon adsorption column 5 is connected to the inlet of the dechlorinated brine storage tank 6 via a pipeline. The brine output from the outlet of the activated carbon adsorption column 5 is the brine after "vacuum degassing treatment" and "activated carbon adsorption treatment," or "treated finished brine." The outlet of the dechlorinated brine storage tank 6 is connected to the primary or secondary brine purification process via a pipeline, thus providing the treated finished brine to the primary or secondary brine purification process. In other words, the treated finished brine output from the outlet of the activated carbon adsorption column 5 is provided to the primary or secondary brine purification process after passing through the dechlorinated brine storage tank 6.

[0037] The outlet of the dechlorination tower 4 is connected to the inlet of the chlorine absorption tower 9 through a pipeline. The outlet of the chlorine absorption tower 9 is connected to the exhaust port of the induced draft fan 10 through a pipeline. The exhaust action of the induced draft fan 10 can create a negative pressure in the pipeline from the outlet of the dechlorination tower 4 to the induced draft fan 10. Driven by this negative pressure, the chlorine gas removed after vacuum degassing in the dechlorination tower 4 can be discharged from the outlet, and after passing through the chlorine absorption tower 9, it reaches the induced draft fan 10 and is then discharged.

[0038] In order to enhance the vacuum degassing effect within the dechlorination tower 4, the dechlorination tower 4 is also equipped with a compressed air inlet (as described above). This compressed air inlet is connected to a compressed air supply source 8 pre-configured on-site. After the compressed air supplied by the compressed air supply source 8 enters the dechlorination tower 4, it can increase the internal pressure of the dechlorination tower, causing the brine to generate a large number of bubbles, which in turn causes the chlorine dissolved in the liquid phase to quickly transfer to the gas phase, thereby promoting the vacuum degassing effect within the dechlorination tower 4.

[0039] It should be noted that the compressed air supply source 8 generally refers to equipment or pipelines that can provide compressed air.

[0040] To further improve degassing efficiency, a heating jacket, essentially an electric heating jacket, is installed outside the dechlorination tower 4. This jacket heats the dechlorination tower 4 and the brine inside, allowing free chlorine in the brine to dissipate more quickly at higher temperatures. This accelerates the vacuum degassing process and enhances its effectiveness. After vacuum degassing, the free chlorine content in the brine can be reduced to 3 mg / L. The temperature of the heating jacket can be controlled by a PLC.

[0041] In addition, to facilitate the sampling of the brine produced by the ion-exchange membrane caustic soda, the recycling device of this embodiment also includes a brine sampling bottle 2. The brine sampling bottle 2 is installed on the pipeline that discharges the brine from the ion-exchange membrane electrolyzer 1. The brine sampling bottle 2 can retain a portion of the brine for sample testing to detect the composition and content of impurities in the brine discharged from the ion-exchange membrane electrolyzer 1.

[0042] This embodiment also provides a method for recycling and treating desalinated brine produced by ion-exchange membrane caustic soda production. This recycling method uses the aforementioned recycling apparatus to treat the desalinated brine produced by the ion-exchange membrane caustic soda process. The recycling method of this embodiment includes the following steps S1 to S2.

[0043] S1, the dechlorination tower 4 is used to perform vacuum degassing treatment on the "dilute brine produced by the ion membrane caustic soda process discharged from the ion membrane electrolyzer 1" in order to remove free chlorine from the dilute brine.

[0044] The free chlorine removed from the brine is converted into chlorine gas. The gas containing chlorine in the dechlorination tower 4 enters the chlorine absorption tower 9 through the pipeline. The chlorine absorption tower 9 removes the chlorine from the gas and then discharges the gas.

[0045] During vacuum degassing, compressed air is blown into the brine in dechlorination tower 4. This can improve the effectiveness of vacuum degassing.

[0046] During vacuum degassing, the heating jacket can be controlled to heat the dechlorination tower 4 and the brine inside, which can speed up the vacuum degassing process.

[0047] S2, activated carbon adsorption column 5 is used to perform activated carbon adsorption treatment on the "vacuum degassed brine" to remove organic pollutants and odors from the brine. This ensures that the recovered brine meets the requirements for reuse.

[0048] The brine that has undergone "vacuum degassing" and "activated carbon adsorption" is the finished brine. The content of free chlorine and organic pollutants is greatly reduced, meeting the water standards for primary or secondary brine refining processes. It can then be returned to the primary or secondary brine refining process of the ion-exchange membrane caustic soda process for use in the salt-dissolving section of primary brine refining or, as needed, directly enter the chelating resin section of secondary brine refining, etc.

[0049] When using the recycling and treatment device and method of this embodiment to treat the brine produced by ion-exchange membrane caustic soda, a dechlorination tower 4 is used to perform vacuum degassing on the brine to remove chlorine. Then, an activated carbon adsorption column 5 is used to perform activated carbon adsorption treatment on the brine after vacuum degassing to remove organic pollutants. The final treated brine has a significantly reduced content of free chlorine and organic pollutants, meeting the water standards for primary or secondary brine refining processes. The treated brine is then supplied to the primary or secondary brine refining processes of the ion-exchange membrane caustic soda process, thereby realizing the reuse of the brine produced by ion-exchange membrane caustic soda, avoiding resource waste, saving costs, and preventing environmental pollution. Vacuum degassing for removing free chlorine from brine, compared to existing methods that typically involve chemical dosing (requiring sodium sulfite to oxidize sulfite to sulfate, and barium chloride for reuse), reduces subsequent sulfate removal processes, saves barium chloride usage, and decreases precipitated sludge discharge while maintaining effective free chlorine removal. Activated carbon adsorption effectively removes organic pollutants from brine, making the ion-exchange membrane caustic soda process suitable for waste salts from pharmaceuticals and pesticides containing high levels of organic matter. Activated carbon adsorption can be activated based on the actual total organic carbon (TOC) content in the brine; an bypass pipeline allows for selection of the process route based on TOC levels, achieving resource utilization and cost reduction.

[0050] The recycling and processing device and method of the present invention have wide applicability. Sodium chloride waste salt generated from the pharmaceutical and pesticide industries can be selected as the electrolytic reaction liquid of the ion membrane electrolyzer 1. Furthermore, the free chlorine and residual total organic carbon in the product brine are thoroughly treated, and the recycling rate of the refined brine is high.

[0051] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, 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. An ion-exchange membrane caustic soda production and dilute brine recycling and recovery treatment device, characterized in that: The device comprises a dechlorination tower (4), an activated carbon adsorption column (5), a chlorine absorption tower (9) and an induced draft fan (10). The liquid inlet of the dechlorination tower (4) receives the dilute brine produced by the ion-exchange membrane caustic soda process, the gas outlet of the dechlorination tower (4) is connected with the gas inlet of the chlorine absorption tower (9), the gas outlet of the chlorine absorption tower (9) is connected with the induced draft fan (10), the liquid outlet of the dechlorination tower (4) is connected with the inlet of the activated carbon adsorption column (5), and the dilute brine discharged from the outlet of the activated carbon adsorption column (5) is used as the treated product dilute brine. The dechlorination tower (4) is used for vacuum degassing treatment of the dilute brine produced by the ion-exchange membrane caustic soda process, and the activated carbon adsorption column (5) is used for activated carbon adsorption treatment of the dilute brine after the vacuum degassing treatment. The dechlorination tower (4) has a compressed air inlet, the compressed air inlet of the dechlorination tower (4) is connected with a compressed air supply source (8), and the compressed air inlet of the dechlorination tower (4) can introduce the compressed air provided by the compressed air supply source (8) into the dechlorination tower (4).

2. The ion-exchange membrane caustic soda production and dilute brine recycling and recovery treatment device according to claim 1, characterized in that: The dechlorination tower (4) is externally provided with a heating jacket.

3. The ion-exchange membrane caustic soda production and dilute brine recycling and recovery treatment device according to claim 1, characterized in that: The recovery treatment device further comprises a chlorine-containing dilute brine storage tank (3), which is arranged before the pipeline through which the dilute brine is received by the liquid inlet of the dechlorination tower (4), and the dilute brine produced by the ion-exchange membrane caustic soda process is discharged from the outlet pipe of the chlorine-containing dilute brine storage tank (3) and enters the liquid inlet of the dechlorination tower (4).

4. The ion-exchange membrane caustic soda production and dilute brine recycling and recovery treatment device according to claim 1, characterized in that: The recovery treatment device further comprises a dechlorinated dilute brine storage tank (6), which is arranged on the pipeline through which the treated product dilute brine is discharged from the outlet of the activated carbon adsorption column (5), and the outlet of the activated carbon adsorption column (5) discharges the treated product dilute brine through the dechlorinated dilute brine storage tank (6).

5. The ion-exchange membrane caustic soda production and dilute brine recycling and recovery treatment device according to claim 1, characterized in that: The recovery treatment device further comprises a dilute brine sampling bottle (2), which is arranged on the pipeline through which the dilute brine is discharged from the ion-exchange membrane electrolytic cell (1).

6. A method for recovering and reusing the dilute brine produced in the production of ion-exchange membrane caustic soda, characterized by: The recovery treatment method comprises: The dilute brine produced by the ion-exchange membrane caustic soda process is subjected to vacuum degassing treatment to remove free chlorine in the dilute brine; The dilute brine after the vacuum degassing treatment is subjected to activated carbon adsorption treatment to remove organic impurities in the dilute brine; When the dilute brine produced by the ion-exchange membrane caustic soda process is subjected to vacuum degassing treatment, compressed air is blown into the dilute brine.

7. The ion-exchange membrane caustic soda production and dilute brine recycling treatment method according to claim 6, characterized in that: The recovery treatment method further comprises: When the dilute brine produced by the ion-exchange membrane caustic soda process is subjected to vacuum degassing treatment, the dilute brine is heated.

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