Recovery device for separating tail gas halogen

Abstract

The invention discloses a recovery device for separating tail gas halogen. The recovery device comprises a spraying box, an alkaline spraying tower, an electrochemical preprocessor and a membrane separator. The spraying box is provided with a first solution cavity and a second solution cavity which are separated from each other; the alkaline spray tower comprises a tower body, spray assemblies, a gas inlet, a gas outlet, a first liquid outlet and a filter screen, the gas outlet and the gas inlet are sequentially formed in the tower body at intervals in the height direction, and the at least three layers of spray assemblies are arranged in the tower body and located between the gas outlet and the gas inlet; the liquid inlet end of the spraying assembly penetrates through the tower body and is communicated with the first solution cavity and the second solution cavity; the liquid inlet end of the electrochemical preprocessor is communicated with the first liquid outlet; the membrane separator is provided with a second liquid outlet and a third liquid outlet, and the liquid inlet end of the membrane separator is communicated with the liquid outlet end of the electrochemical preprocessor. According to the invention, the gradient separation and recovery of fluorine, bromine and chlorine are realized by utilizing a synergistic spraying mode of a weak alkali solution and a strong alkali solution and combining electrochemical regulation and membrane separation technologies.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste resource utilization and pollution control, and in particular to a recovery device for separating tail gas halogen. Background Art

[0002] Liquid crystal displays (LCDs) are crucial components in electronic display devices, widely used in a wide range of everyday electronic devices, including computers, LCD TVs, tablets, and mobile phones. However, as these products reach the end of their useful lives, the number of discarded electronic products is expected to grow exponentially, and so too will the volume of discarded LCDs. Discarded LCDs are broadly divided into components, including the LCD panel, film assembly, and backlight module. The LCD panel, as the core component, consists of polarizers, an upper glass substrate, liquid crystals, and a lower glass substrate. As the primary component of recycling, physical disassembly methods, such as mechanical grinding to separate the liquid crystals, are currently commonly used to recycle the glass.

[0003] Liquid crystal powder obtained by mechanical grinding can be safely disposed of via pyrolysis. However, due to the complex composition of liquid crystal materials, the volatile phase products of pyrolysis contain halogenated organic compounds, which, if improperly handled, can seriously pollute the environment. Therefore, in-situ combustion is required to treat the pyrolysis oil and gas from waste liquid crystals. This method can remove most pollutants in the pyrolysis oil and gas, but in-situ combustion of the halogenated organic compounds in the pyrolysis oil and gas produces halogenated acidic gases (HF, HCl, and HBr). If discharged directly without treatment, it will not only harm the surrounding environment and human health, but also its corrosive nature will shorten the service life of industrial equipment and may cause industrial safety accidents. Current exhaust gas treatment equipment typically only performs simple spraying and filtration of the exhaust gas, resulting in low treatment efficiency and ineffective separation of fluorine, bromine, and chlorine elements from the exhaust gas. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the current tail gas treatment equipment usually only performs simple spraying and filtering treatment on the tail gas after the in-situ combustion of waste liquid crystal pyrolysis oil and gas, with low treatment efficiency and inability to effectively separate the fluorine, bromine and chlorine elements in the tail gas.

[0005] In order to solve the above technical problems, the present invention provides a recovery device for separating halogen from tail gas, comprising:

[0006] The spray box has a first solution chamber and a second solution chamber that are separated, wherein the first solution chamber is used to be filled with a weak alkaline solution, and the second solution chamber is used to be filled with a strong alkaline solution;

[0007] An alkaline spray tower comprises a tower body, a spray assembly, an air inlet, an air outlet, a first liquid outlet, and a filter screen, wherein the air outlet and the air inlet are sequentially spaced apart in the tower body along the height direction, at least three layers of the spray assembly are sequentially spaced apart in the tower body along the height direction and are located between the air outlet and the air inlet, the first liquid outlet is located at the bottom of the tower body, and the filter screen is provided at the first liquid outlet, the liquid inlet end of the spray assembly passes through the tower body and is in communication with the first solution cavity and the second solution cavity, so as to spray the tail gas in the tower body and remove the fluoride therein;

[0008] an electrochemical pre-processor, whose liquid inlet is connected to the first liquid outlet, for pre-processing the solution flowing out of the tower body so that the chloride ions and the bromide ions form a radius difference;

[0009] A membrane separator has a second liquid outlet and a third liquid outlet. The liquid inlet end of the membrane separator is connected to the liquid outlet end of the electrochemical preprocessor to perform membrane separation treatment on the solution, so that the bromine-containing solution is discharged through the second liquid outlet and the chlorine-containing solution is discharged through the third liquid outlet.

[0010] Furthermore, it also includes a bubble generator, and the liquid outlet end of the bubble generator is connected to the spray box.

[0011] Furthermore, the alkaline spray tower further comprises a packing layer, which is arranged in the tower body and located above the spray assembly on the top layer.

[0012] Furthermore, the packing layer includes a skeleton and hollow spheres, the skeleton is filled with a plurality of the hollow spheres, and the hollow spheres are filled with quicklime to absorb the waste gas that has not been completely treated.

[0013] Furthermore, the spray assembly includes a first water pump, a spray pipe, and a plurality of nozzles arranged in sequence along the extension direction of the spray pipe. One end of the spray pipe passes through the tower body and is connected to the first solution cavity and the second solution cavity. The first water pump is installed at one end of the spray pipe close to the spray box.

[0014] Furthermore, the electrochemical preprocessor includes a first body, a scraper, a first drive, an aeration plate, an anode, a cathode, a pulse power supply, a first infusion tube and a first valve body. The liquid inlet end of the first body is connected to the first liquid outlet through the first infusion tube. The first infusion tube is installed with the first valve body. The scraper is rotatably installed in the first body. The first drive is connected to the scraper to scrape off flocs floating to the surface of the solution. The aeration plate is installed at the bottom of the first body. The anode and the cathode are arranged in the first body and are connected to the pulse power supply to pretreat the solution.

[0015] Furthermore, the anode and the cathode are both porous electrodes, and the pulse power supply is a unidirectional pulse power supply.

[0016] Furthermore, the membrane separator includes a second body, a connecting pipe having the second liquid outlet, a nanofiltration membrane separation component, an ultrasonic rod, a second water pump, a liquid outlet pipe having the third liquid outlet, a second infusion pipe and a second valve body. The liquid inlet end of the second body is connected to the liquid outlet end of the electrochemical preprocessor through the second infusion pipe. The second infusion pipe is installed with the second valve body. One end of the connecting pipe is connected to the liquid inlet end of the second body. Multiple nanofiltration membrane separation components are arranged in the second body in sequence along the length direction of the connecting pipe, and one end of the nanofiltration membrane separation component is connected to the connecting pipe. The other end of each nanofiltration membrane separation component is connected to the liquid outlet pipe in sequence. The end of the liquid outlet pipe close to the third liquid outlet is connected to the second water pump. One end of the ultrasonic rod is externally connected to an ultrasonic generator, and the other end is located at the bottom of the corresponding nanofiltration membrane separation component.

[0017] Furthermore, the second body has a third cavity for accommodating the nanofiltration membrane separation component, the ultrasonic rod and the conductive liquid, and the bottom end surface of the nanofiltration membrane separation component is in contact with the liquid surface of the conductive liquid.

[0018] Furthermore, the ultrasonic rod is placed in a direction perpendicular to the direction in which the solution flows through the nanofiltration membrane separation component.

[0019] Compared with the prior art, the recovery device for separating halogen from tail gas according to the embodiment of the present invention has the following advantages:

[0020] The tail gas of the embodiment of the present invention first enters the tower body through the air inlet, and the strong alkaline solution and weak alkaline solution in the spray box flow to the spray components of different layers respectively. The two spray liquids alternately treat the tail gas, first spraying with the strong alkaline solution to precipitate the fluoride into CaF2, and then spraying with the weak alkaline solution to fully absorb HCl and HBr. After the three-stage spray treatment, the gas is discharged from the top air outlet, and the chlorine / bromine solution is discharged from the first liquid outlet. The chlorine / bromine solution enters the electrochemical pretreatment device to pretreat the solution to oxidize Br in the solution. - Generate BrO3 -, so that the chlorine and bromide ions form a radius difference. The solution after pretreatment enters the membrane separator, where the solution is separated. The bromine-containing solution retained by the membrane is discharged from the second liquid outlet, and the chlorine-containing solution is discharged from the third liquid outlet. This embodiment uses a multi-stage treatment system to improve the removal rate of acidic gases in the tail gas. The weak base solution and the strong base solution work together to spray, and the fluoride is preferentially crystallized under the action of calcium ions to remove fluoride. At the same time, electrochemical control and membrane separation technology are used to achieve the cascade separation and recovery of fluorine, bromine, and chlorine. The operation is simple and the treatment efficiency is high, ensuring that the treated tail gas emissions meet environmental protection standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 1 is a schematic structural diagram of a recovery device for separating halogen from tail gas provided by an embodiment of the present invention;

[0022] Figure 2 Schematic diagram of the structure of the spray box and alkaline spray tower provided in an embodiment of the present invention;

[0023] Figure 3 Schematic diagram of the structure of the electrochemical preprocessor provided by an embodiment of the present invention;

[0024] Figure 4 1 is a schematic structural diagram of a membrane separator provided by an embodiment of the present invention;

[0025] In the figure, 1, spray box; 11, first solution chamber; 12, second solution chamber; 2, alkaline spray tower; 21, tower body; 22, spray assembly; 221, first water pump; 222, spray pipe; 223, nozzle; 23, air inlet; 24, air outlet; 25, first liquid outlet; 26, filter; 27, packing layer; 3, electrochemical pre-processor; 31, first body; 32, scraper; 33, aeration plate; 34 , anode; 35, cathode; 36, pulse power supply; 37, first infusion tube; 38, first valve body; 4, membrane separator; 41, second liquid outlet; 42, third liquid outlet; 43, second body; 431, third cavity; 44, connecting pipe; 45, nanofiltration membrane separation component; 46, ultrasonic rod; 47, second water pump; 48, liquid outlet pipe; 49, second infusion tube; 410, second valve body; 5, bubble generator. DETAILED DESCRIPTION

[0026] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0027] like Figure 1 and Figure 2As shown, the present invention provides a recovery device for separating halogen from exhaust gas. The device processes exhaust gas from in-situ combustion of waste liquid crystal pyrolysis oil and gas to sequentially separate the halogen. The recovery device comprises a spray box 1, an alkaline spray tower 2, an electrochemical pre-processor 3, and a membrane separator 4. The spray box 1 has a first solution chamber 11 and a second solution chamber 12, each of which is separated. The first solution chamber 11 is filled with a weak alkaline solution, and the second solution chamber 12 is filled with a strong alkaline solution. The alkaline spray tower 2 comprises a tower body 21, a spray assembly 22, an air inlet 23, an air outlet 24, a first liquid outlet 25, and a filter 26. The air outlet 24 and the air inlet 23 are spaced apart along the height of the tower body 21. At least three layers of spray assemblies 22 are spaced apart along the height of the tower body 21, located between the air outlet 24 and the air inlet 23. Multi-stage spraying increases the gas-liquid contact area, enhances absorption efficiency, and ensures a more complete reaction with the exhaust gas. Among them, the gas outlet 24 is located at the top of the tower body 21, the first liquid outlet 25 is located at the bottom of the tower body 21, and a filter 26 is provided at the first liquid outlet 25 to intercept CaF2 precipitation; the liquid inlet end of the spray assembly 22 passes through the tower body 21 and communicates with the first solution chamber 11 and the second solution chamber 12 to spray the exhaust gas in the tower body 21 and remove the fluoride therein; the liquid inlet end of the electrochemical preprocessor 3 is communicated with the first liquid outlet 25 to pre-treat the solution flowing out of the tower body 21, so that the chloride ions and bromide ions form a radius difference under the action of the electric field, preparing for subsequent membrane separation; the membrane separator 4 has a second liquid outlet 41 and a third liquid outlet 42. The liquid inlet end of the membrane separator 4 is communicated with the liquid outlet end of the electrochemical preprocessor 3 to perform membrane separation treatment on the solution. By utilizing the selective permeability of the membrane, the bromine-containing solution is discharged through the second liquid outlet 41 and the chlorine-containing solution is discharged through the third outlet 42.

[0028] Based on the above structure, the tail gas first enters the tower body 21 through the air inlet 23, and the strong alkaline solution and weak alkaline solution in the spray box 1 flow to the spray components 22 of different layers respectively. The two spray liquids alternately treat the tail gas. First, the strong alkaline solution is sprayed to precipitate the fluoride into CaF2, and then the weak alkaline solution is sprayed to fully absorb HCl and HBr. After the three-stage spray treatment, the gas is discharged from the top outlet 24, and the chlorine / bromine solution is discharged from the first liquid outlet 25. The chlorine / bromine solution enters the electrochemical pretreatment device to pretreat the solution to oxidize Br in the solution. - Generate BrO3 -, so that the chlorine and bromide ions form a radius difference. The solution after pretreatment enters the membrane separator 4, where the solution is separated. The bromine-containing solution retained by the membrane is discharged from the second liquid outlet 41, and the chlorine-containing solution is discharged from the third liquid outlet 42. This embodiment uses a multi-stage treatment system to improve the removal rate of acidic gases in the tail gas. The weak alkaline solution and the strong alkaline solution are sprayed in a synergistic manner. Fluoride is preferentially crystallized under the action of calcium ions to remove fluoride. At the same time, electrochemical control and membrane separation technology are combined to achieve the cascaded separation and recovery of fluorine, bromine, and chlorine. The operation is simple and the treatment efficiency is high, ensuring that the treated tail gas emissions meet environmental protection standards.

[0029] It should be noted that the strong alkaline solution and weak alkaline solution in the spray box 1 of this embodiment flow to the spray components 22 at different levels respectively, and the two spray liquids alternately treat the tail gas as follows: the strong alkaline solution flows to the spray component 22 at the bottom, and the weak alkaline solution flows to the spray component 22 at the upper level. As the tail gas rises, it first contacts the strong alkaline solution spray liquid at the bottom. The pH of the strong alkaline solution is greater than 12, such as calcium hydroxide (Ca(OH)2) or sodium hydroxide (NaOH) solution. Fluoride (such as HF, NaF, etc.) reacts with calcium ions (Ca(OH)2) under strong alkaline conditions. 2+ ) undergoes the following reaction: Ca 2+ +2F-→CaF2↓, to form insoluble calcium fluoride (CaF2) precipitation, preferentially removing highly toxic fluorides in the exhaust gas. This prevents subsequent absorbents from being saturated with fluoride ions, which would affect the absorption of other acidic gases. Subsequently, as the exhaust gas rises, it comes into contact with the weak alkaline solution spray located in the upper layer. The pH of the weak alkaline solution is controlled at around 8-10, such as sodium carbonate (Na2CO3), sodium bicarbonate (NaHCO3), or limestone slurry. Since the exhaust gas itself contains HCl and HBr, and reacts with strong alkaline solutions to produce HCl and HBr, the following reactions occur in a weakly alkaline environment (such as Na2CO3 solution): Na2CO3+2HCl→2NaCl+CO2↑+H2O; Na2CO3+2HBr→2NaBr+CO2↑+H2O, allowing HCl and HBr to be effectively neutralized and absorbed.

[0030] Furthermore, a bubble generator 5 is included, and the liquid outlet of the bubble generator 5 is connected to the liquid inlet of the spray box 1. In this embodiment, air or other gas is injected into the liquid through the bubble generator 5 to form a large number of fine bubbles, and then its liquid outlet is connected to the spray box 1, so that the liquid with bubbles will eventually be sprayed out through the spray assembly 22. When the liquid containing bubbles is sprayed, the bubbles can disperse the liquid into smaller droplets or increase the surface area inside the liquid to increase the contact area between the liquid and the gas in the exhaust gas, thereby enhancing the absorption effect. It should be noted that a valve body (not shown in the figure) is provided on the connecting pipe between the bubble generator 5 and the spray box 1 of this embodiment, which is used to control the opening and closing of the connecting pipe. At the same time, the flow rate of the fluid flowing to the spray box can be controlled by the valve body.

[0031] It should also be noted that the bubble generator 5 of this embodiment is a conventional ultrafine bubble generator, and its structure is not particularly limited here.

[0032] Furthermore, the alkaline spray tower 2 also includes a packing layer 27, which is arranged in the tower body 21 and located above the top-most spray assembly 22. As the last barrier in the treatment process of the alkaline spray tower 2, the packing layer 27 can enable the halogen-containing acidic gas that is not completely absorbed to be further absorbed and treated by the packing layer 27, ensuring that the exhaust gas meets environmental protection standards.

[0033] Furthermore, the packing layer 27 includes a skeleton and hollow spheres, and the skeleton is filled with a plurality of hollow spheres. The hollow spheres are usually made of corrosion-resistant materials, such as plastic or ceramic, and have holes on their surfaces or walls to allow gas to pass through and contact the internal substances. The hollow spheres are filled with quicklime, which can react chemically with acidic gases (such as HCl, SO2, etc.) to generate stable salts to absorb incompletely treated exhaust gas, so that the exhaust gas reaches a higher degree of purification and prevents the exhaust gas from directly overflowing without treatment.

[0034] like Figure 2 As shown, the spray assembly 22 includes a first water pump 221, a spray pipe 222, and a plurality of nozzles 223 arranged in sequence along the extension direction of the spray pipe 222. The spray pipe 222 is used to transport liquid, and the nozzles 223 are used to spray the liquid into a mist or a thin stream at a certain pressure. Through the arrangement of multiple nozzles 223, the liquid can be more evenly covered over the target area, improving the spraying efficiency and effect. One end of the spray pipe 222 passes through the tower body 21 and is connected to the first solution chamber 11 and the second solution chamber 12. The first water pump 221 is used to provide power. It is installed at one end of the spray pipe 222 near the spray box 1 to pump the corresponding solution to the nozzles 223 for spraying as needed.

[0035] It should be noted that the nozzle 223 of this embodiment is an atomizing nozzle or a fan nozzle. The atomizing nozzle is used to break the liquid into very fine droplets, forming a mist, which helps to increase the contact area between the liquid and the gas, thereby improving mass transfer efficiency. The fan nozzle is used to spray the liquid in a flat fan pattern, providing a more uniform coverage method and ensuring uniform distribution of the liquid throughout the spray area.

[0036] like Figure 1 and Figure 3 As shown, the electrochemical pre-processor 3 includes a first body 31, a scraper 32, a first drive member (not shown in the figure), an aeration plate 33, an anode 34, a cathode 35, a pulse power supply 36, a first liquid infusion pipe 37 and a first valve body 38. The first body 31 is the main container of the entire device, used to contain the liquid to be treated. Its liquid inlet end is connected to the first liquid outlet 25 through the first liquid infusion pipe 37, and the solution can flow into and out of the first body 31. The first liquid infusion pipe 37 is installed at one end near the liquid inlet end of the first body 31. The first valve body 38 is used to control the opening and closing of the first liquid infusion pipe 37 and control the flow rate of the solution into the first body 31 through the first valve body 38. The scraper 32 is rotatably installed in the first body 31. The first drive member is connected to the scraper 32 to scrape off flocculants that float to the surface of the solution to prevent them from redissolving or affecting the subsequent treatment effect. The aeration plate 33 is installed at the bottom of the first body 31. By injecting air or oxygen into the liquid, the flotation process is promoted, so that light pollutants (such as flocculants) float to the surface, which is convenient for the scraper 32 to remove. The anode 34 and the cathode 35 serve as electrodes for the electrochemical reaction. They are arranged in the first body 31 and are connected to the pulse power supply 36. The pulse power supply 36 is used to apply voltage at different stages to induce the electrochemical reaction to pre-treat the solution.

[0037] Based on the above structure, this embodiment adopts two stages to pre-treat the solution. The first stage is the low potential stage: at a relatively low voltage, an electro-flocculation or electro-flotation reaction occurs, causing the charged colloidal particles to become unstable and aggregate to form flocs. At the same time, the bubbles generated by the aeration disk 33 drive these flocs to float to the liquid surface, and the scraper 32 scrapes off the scum to complete the initial purification.

[0038] The second stage is the high potential stage: at a higher voltage, the cathode 35 / anode 34 reaction is enhanced, and the bromide ions in the solution undergo the following reaction: Br - +3H2O→BrO3 - +6H + +6e - , so that Br - Oxidized to BrO3 - In addition, due to Br - After oxidation, Cl - With Br -The larger the difference in ionic radius, the easier it is to remove the two ions separately through membrane separation or other physical methods. This embodiment uses a phased process to first remove colloidal impurities, preemptively removing a large amount of suspended matter and some organic matter, reducing the burden on subsequent processing systems. It then changes the ionic form, making the subsequent separation process more efficient.

[0039] Preferably, the anode 34 and cathode 35 of this embodiment are both porous electrodes, which can increase the effective reaction area of ​​the electrode, thereby improving the efficiency of the electrochemical reaction. Common porous electrode materials include activated carbon, graphite felt, titanium-based coating electrodes (such as Ti / PbO2, Ti / SnO2), etc. The pulse power supply 36 of this embodiment is preferably a unidirectional pulse power supply to better control the oxidation or reduction process of the electrode. It can be understood that in the low potential stage, the porous electrode combined with the unidirectional pulse power supply 36 can induce electrocoagulation / electroflotation of colloidal particles, thereby improving the efficiency of flocculant generation; in the high potential stage, the porous electrode is Br - Provides a larger reaction area to oxidize to generate BrO3 - ; while the unidirectional pulse prevents unnecessary reduction reactions from interfering with this process.

[0040] It should be noted that the anode 34 and cathode 35 of this embodiment may also be flat electrodes. The flat shape can provide a larger surface area and help achieve a more uniform current distribution on the entire electrode surface to improve the efficiency of the electrochemical reaction.

[0041] like Figure 1 and Figure 4As shown, the membrane separator 4 includes a second body 43, a connecting pipe 44 with a second liquid outlet 41, a nanofiltration membrane separation component 45, an ultrasonic rod 46, a second water pump 47, a liquid outlet pipe 48 with a third liquid outlet 42, a second liquid infusion pipe 49 and a second valve body 410. The second body 43 is the main container of the entire membrane separation device, and its liquid inlet end is connected to the liquid outlet end of the electrochemical preprocessor 3 through the second liquid infusion pipe 49. One end of the connecting pipe 44 is connected to the liquid inlet end of the second body 43. Multiple nanofiltration membrane separation components 45 are arranged in the second body 43 in sequence along the length direction of the connecting pipe 44, and one end of the nanofiltration membrane separation component 45 is connected to the connecting pipe 44, so that the pretreated solution flows along the connecting pipe 44 to the nanofiltration membrane separation component 45 for membrane separation treatment; the second liquid infusion pipe 49 is installed with a second valve body 410 for controlling the opening and closing of the second liquid infusion pipe 49, and at the same time controlling the flow rate of the solution flowing into the connecting pipe 44 through the second valve body 410. The other end of each nanofiltration membrane separation assembly 45 is in turn connected to a liquid outlet pipe 48. The end of the liquid outlet pipe 48 near the third liquid outlet 42 is connected to a second water pump 47. The second water pump 47 is used to provide power to pump the separated chlorine-containing solution from the nanofiltration membrane separation assembly 45 to the liquid outlet pipe 48, and then out of the third liquid outlet 42. An ultrasonic rod 46 is connected to an ultrasonic generator at one end and located at the bottom of the corresponding nanofiltration membrane separation assembly 45 at the other end. This generates vibration or cavitation effects through ultrasonic waves, promoting the flow of the solution on the membrane surface of the nanofiltration membrane separation assembly 45 and improving separation efficiency.

[0042] Based on the above structure, the pretreated solution enters the connecting pipe 44, and the solution flows through a plurality of nanofiltration membrane separation components 45, and is separated by the selective permeability of the membrane. After the bromine-containing solution is retained by the membrane, it is discharged from the second liquid outlet 41. Smaller chlorine molecules can pass through the membrane, so that the chlorine-containing solution is pumped by the second water pump 47 and discharged from the third liquid outlet 42. In this process, the ultrasonic wave generated by the ultrasonic rod 46 can prevent membrane contamination, enhance mass transfer efficiency, and thus improve the separation effect. This embodiment utilizes the selective permeability of the nanofiltration membrane separation component 45 to different ions (such as bromide ions and chloride ions) to achieve effective separation of bromine molecules and chlorine molecules in the solution. It should be noted that the nanofiltration membrane separation component 45 of this embodiment is a conventional membrane separation device, and its structure is not particularly limited here.

[0043] Furthermore, the second body 43 has a third chamber 431 for accommodating the nanofiltration membrane separation component 45, the ultrasonic rod 46, and the conductive liquid. The bottom end surface of the nanofiltration membrane separation component 45 contacts the liquid surface of the conductive liquid. The conductive liquid in the third chamber 431 acts as a bridge to effectively transfer the vibration energy generated by the ultrasonic rod 46 to the membrane surface, thereby promoting the separation process. The conductive liquid can be water or other solutions containing different components, which are not particularly limited here. Preferably, the length of the portion of the nanofiltration membrane separation component 45 immersed in the conductive liquid accounts for at least one-third of the overall length, so that when the nanofiltration membrane separation component 45 is in more complete contact with the conductive liquid, the ultrasonic energy can fully reach the membrane surface, thereby improving the cleaning efficiency or mass transfer efficiency.

[0044] Furthermore, the ultrasonic rod 46 is placed in a direction perpendicular to the direction in which the solution flows through the nanofiltration membrane separation component 45. In this embodiment, the solution in the membrane separator 4 flows sequentially through the nanofiltration membrane separation component 45 along a certain direction, and the ultrasonic rod 46 is installed below or near the membrane component in a manner perpendicular to the flow direction. For example, the solution flows sequentially through the nanofiltration membrane component from left to right in the horizontal direction, and the ultrasonic rod 46 is placed in a vertical direction, and the emitted ultrasonic waves act on the membrane surface from bottom to top. When the ultrasonic rod 46 is perpendicular to the direction of liquid flow, the range of action of the ultrasonic wave can cover the entire membrane surface more evenly. In the process of passing through the membrane component, the solution will continue to be affected by the ultrasonic wave from the vertical direction, which increases the residence time of the liquid in the ultrasonic field, reduces energy waste, and thus improves the ultrasonic treatment effect on the solution. If the ultrasonic rod 46 is parallel to the flow direction, the ultrasonic wave may be quickly carried away, resulting in the energy not being able to fully act on the membrane surface and flowing out with the liquid; the vertical arrangement allows the ultrasonic wave to act more concentratedly on key areas (such as the membrane surface).

[0045] The specific steps are as follows:

[0046] S1: The tail gas after the in-situ combustion of waste liquid crystal pyrolysis oil and gas first enters the alkaline spray tower 2 through the air inlet 23. The tail gas first contacts the sprayed strong alkaline solution to precipitate fluoride as CaF2. As the tail gas rises, it contacts the sprayed weak alkaline solution to fully absorb HCl and HBr in the tail gas. After the three-stage spray treatment, the gas passes through the packing layer 27 and is discharged from the top air outlet 24. The chlorine / bromine solution is discharged from the first liquid outlet 25. The first liquid outlet 25 is provided with a filter 26 to intercept the CaF2 precipitate.

[0047] S2: The chlorine / bromine solution enters the electrochemical pretreatment device and is aerated through the aeration plate 33 at the bottom. The anode 34 and the cathode 35 are connected to an external pulse power supply 36. The colloidal impurities in the solution are first treated at the low potential stage, and the flocculants floating to the surface of the solution are scraped off by the scraper 32. Then, the Br in the solution is oxidized at the high potential stage. - Generate BrO3- , so that the chlorine and bromide ions form a radius difference, and the solution after pretreatment is discharged through the second valve body 410.

[0048] S3: The pretreated solution finally enters the membrane separator 4. An ultrasonic rod 46 is provided at the bottom of the second body 43. The ultrasonic action promotes the separation process of the solution in the nanofiltration membrane separation component 45. The bromine-containing solution retained by the membrane is discharged from the second liquid outlet 41, and the chlorine-containing solution is pumped out from the third liquid outlet 42 by the second water pump 47.

[0049] In summary, the embodiment of the present invention provides a recovery device for separating halogen from tail gas. The tail gas first enters the tower body 21 through the air inlet 23. The strong alkaline solution and the weak alkaline solution in the spray box 1 flow to the spray components 22 of different layers respectively. The two spray liquids alternately treat the tail gas. First, the strong alkaline solution is sprayed to precipitate the fluoride into CaF2, and then the weak alkaline solution is sprayed to fully absorb HCl and HBr. After the three-stage spray treatment, the gas is discharged from the top air outlet 24, and the chlorine / bromine solution is discharged from the first liquid outlet 25. The chlorine / bromine solution enters the electrochemical pretreatment device to pretreat the solution to oxidize Br in the solution. - Generate BrO3 - , so that the chlorine and bromide ions form a radius difference. The solution after pretreatment enters the membrane separator 4, where the solution is separated. The bromine-containing solution retained by the membrane is discharged from the second liquid outlet 41, and the chlorine-containing solution is discharged from the third liquid outlet 42. This embodiment uses a multi-stage treatment system to improve the removal rate of acidic gases in the tail gas. The weak alkaline solution and the strong alkaline solution are sprayed in a synergistic manner. Fluoride is preferentially crystallized under the action of calcium ions to remove fluoride. At the same time, electrochemical control and membrane separation technology are combined to achieve the cascaded separation and recovery of fluorine, bromine, and chlorine. The operation is simple and the treatment efficiency is high, ensuring that the treated tail gas emissions meet environmental protection standards.

[0050] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A recovery device for separating halogen from tail gas, characterized in that: include: The spray box has a first solution chamber and a second solution chamber that are separated, wherein the first solution chamber is used to be filled with a weak alkaline solution, and the second solution chamber is used to be filled with a strong alkaline solution; An alkaline spray tower comprises a tower body, a spray assembly, an air inlet, an air outlet, a first liquid outlet, and a filter screen, wherein the air outlet and the air inlet are sequentially spaced apart in the tower body along the height direction, at least three layers of the spray assembly are sequentially spaced apart in the tower body along the height direction and are located between the air outlet and the air inlet, the first liquid outlet is located at the bottom of the tower body, and the filter screen is provided at the first liquid outlet, the liquid inlet end of the spray assembly passes through the tower body and is in communication with the first solution cavity and the second solution cavity, so as to spray the tail gas in the tower body and remove the fluoride therein; an electrochemical pre-processor, whose liquid inlet is connected to the first liquid outlet, for pre-processing the solution flowing out of the tower body so that the chloride ions and the bromide ions form a radius difference; A membrane separator has a second liquid outlet and a third liquid outlet. The liquid inlet end of the membrane separator is connected to the liquid outlet end of the electrochemical preprocessor to perform membrane separation treatment on the solution, so that the bromine-containing solution is discharged through the second liquid outlet and the chlorine-containing solution is discharged through the third liquid outlet.

2. The recovery device for separating tail gas halogen according to claim 1, characterized in that: It also includes a bubble generator, and the liquid outlet end of the bubble generator is connected to the spray box.

3. The recovery device for separating tail gas halogen according to claim 1, characterized in that: The alkaline spray tower further comprises a packing layer, which is arranged in the tower body and located above the spray assembly at the top layer.

4. The recovery device for separating tail gas halogen according to claim 3, characterized in that: The packing layer includes a skeleton and hollow spheres. The skeleton is filled with a plurality of the hollow spheres, and the hollow spheres are filled with quicklime to absorb the waste gas that has not been completely treated.

5. The recovery device for separating tail gas halogen according to claim 1, characterized in that: The spray assembly includes a first water pump, a spray pipe, and a plurality of nozzles arranged in sequence along the extension direction of the spray pipe. One end of the spray pipe passes through the tower body and is connected to the first solution cavity and the second solution cavity. The first water pump is installed at one end of the spray pipe close to the spray box.

6. The recovery device for separating halogen from tail gas according to claim 1, characterized in that: The electrochemical preprocessor includes a first body, a scraper, a first drive, an aeration plate, an anode, a cathode, a pulse power supply, a first infusion tube and a first valve body. The liquid inlet end of the first body is connected to the first liquid outlet through the first infusion tube. The first infusion tube is equipped with the first valve body. The scraper is rotatably installed in the first body. The first drive is connected to the scraper to scrape off flocs floating to the surface of the solution. The aeration plate is installed at the bottom of the first body. The anode and the cathode are arranged in the first body and are connected to the pulse power supply to pretreat the solution.

7. The recovery device for separating halogen from tail gas according to claim 6, characterized in that: The anode and the cathode are both porous electrodes, and the pulse power supply is a unidirectional pulse power supply.

8. The recovery device for separating halogen from tail gas according to claim 1, characterized in that: The membrane separator includes a second body, a connecting pipe with the second liquid outlet, a nanofiltration membrane separation component, an ultrasonic rod, a second water pump, a liquid outlet pipe with the third liquid outlet, a second infusion pipe and a second valve body. The liquid inlet end of the second body is connected to the liquid outlet end of the electrochemical preprocessor through the second infusion pipe. The second infusion pipe is installed with the second valve body. One end of the connecting pipe is connected to the liquid inlet end of the second body. Multiple nanofiltration membrane separation components are arranged in the second body in sequence along the length direction of the connecting pipe, and one end of the nanofiltration membrane separation component is connected to the connecting pipe. The other end of each nanofiltration membrane separation component is connected to the liquid outlet pipe in sequence. The end of the liquid outlet pipe close to the third liquid outlet is connected to the second water pump. One end of the ultrasonic rod is externally connected to an ultrasonic generator, and the other end is located at the bottom of the corresponding nanofiltration membrane separation component.

9. The recovery device for separating halogen from tail gas according to claim 8, characterized in that: The second body has a third cavity for accommodating the nanofiltration membrane separation component, the ultrasonic rod and the conductive liquid. The bottom end surface of the nanofiltration membrane separation component is in contact with the liquid surface of the conductive liquid.

10. The recovery device for separating halogen from tail gas according to claim 8, characterized in that: The ultrasonic rod is placed in a direction perpendicular to the direction in which the solution flows through the nanofiltration membrane separation component.

Images