A recovery apparatus for separating tail gas halogens

Abstract

The application discloses a recovery device for separating tail gas halogen, comprising a spraying box, an alkaline spraying tower, an electrochemical pretreater and a membrane separator. The spraying box is provided with a first solution cavity and a second solution cavity which are separated. The alkaline spraying tower comprises a tower body, a spraying assembly, an air inlet, an air outlet, a first liquid outlet and a filter screen. The air outlet and the air inlet are sequentially and spacedly arranged in the height direction of the tower body. At least three layers of spraying assemblies are arranged in the tower body and located between the air outlet and the air inlet. The liquid inlet end of the spraying assembly is communicated with the first solution cavity and the second solution cavity through the tower body. The liquid inlet end of the electrochemical pretreater is communicated with the first liquid outlet. The membrane separator is provided with a second liquid outlet and a third liquid outlet. The liquid inlet end of the membrane separator is communicated with the liquid outlet end of the electrochemical pretreater. The weak alkali solution and the strong alkali solution are sprayed in a cooperative mode, and the electrochemical regulation and the membrane separation technology are simultaneously used, so that the fluorine, bromine and chlorine are separated and recovered in stages.

Description

TECHNICAL FIELD

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

[0002] Liquid crystal display is an important component in electronic display equipment, which is widely used in many daily electronic devices such as computers, liquid crystal televisions, tablet computers and mobile phones. However, with the end of service life, the number of waste electronic products will increase exponentially, and the number of waste liquid crystal displays will also increase explosively. Waste liquid crystal displays are roughly divided into liquid crystal panels, thin film sets and backlight lamp modules, among which the liquid crystal panel, as the core part, is composed of a polarizer, an upper glass substrate, liquid crystal and a lower glass substrate. As the main part of recycling, it is currently separated by physical disassembly methods, such as mechanical grinding method to separate the liquid crystal, thereby realizing the recycling of glass.

[0003] The liquid crystal powder obtained by mechanical grinding can be safely disposed of by pyrolysis, but due to the complex composition of liquid crystal materials, halogenated organic compounds are contained in the pyrolysis volatile phase products. If not properly handled, it will seriously pollute the environment. Therefore, it is necessary to further treat the pyrolysis oil gas of waste liquid crystal by in-situ combustion method, which can remove most of the pollutants in the pyrolysis oil gas. However, halogenated organic compounds in the pyrolysis oil gas will generate halogen-containing acid gases (HF, HCl and HBr) after in-situ combustion. If not treated directly, on the one hand, it will cause harm to the surrounding environment and human health; on the other hand, its corrosive nature will shorten the service life of industrial equipment and may cause industrial accidents. The current tail gas treatment equipment usually only sprays and filters the tail gas, which has low treatment efficiency and cannot effectively separate fluorine, bromine and chlorine elements in the tail gas. SUMMARY

[0004] The technical problem to be solved by the present application is that the current tail gas treatment equipment usually only sprays and filters the tail gas after in-situ combustion of waste liquid crystal pyrolysis oil gas, which has low treatment efficiency and cannot effectively separate fluorine, bromine and chlorine elements in the tail gas.

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

[0006] The spray tank has a first solution cavity and a second solution cavity arranged separately, the first solution cavity is used to fill weak alkali solution, and the second solution cavity is used to fill strong alkali solution;

[0007] The alkaline spray tower comprises a tower body, a spray assembly, an air inlet, an air outlet, a first liquid outlet and a filter screen, the air outlet and the air inlet are sequentially and spacedly arranged in the height direction of the tower body, at least three layers of the spray assembly are sequentially and spacedly arranged in the tower body and located between the air outlet and the air inlet, the first liquid outlet is located at the bottom of the tower body, the filter screen is arranged at the first liquid outlet, the liquid inlet end of the spray assembly communicates with the first solution cavity and the second solution cavity through the tower body, and the spray assembly sprays tail gas in the tower body and removes fluoride therein;

[0008] An electrochemical pretreater, a liquid inlet end of which communicates with the first liquid outlet, is used to pretreat the solution flowing out of the tower body, so that the radius difference of chloride ions and bromide ions is formed;

[0009] A membrane separator having a second liquid outlet and a third liquid outlet, a liquid inlet end of the membrane separator communicates with the liquid outlet end of the electrochemical pretreater, so that the solution is subjected to membrane separation treatment, 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] Further, a bubble generator is further included, a liquid outlet end of the bubble generator communicates with the spray tank.

[0011] Further, the alkaline spray tower further comprises a filler layer, the filler layer is arranged in the tower body and located above the spray assembly of the top layer.

[0012] Further, the filler layer comprises a skeleton and a hollow sphere, the skeleton is filled with a plurality of the hollow spheres, and the hollow spheres are filled with quicklime to absorb the exhaust gas which is not completely treated.

[0013] Further, the spray assembly comprises a first water pump, a spray pipe and a plurality of nozzles which are sequentially and spacedly arranged along the extension direction of the spray pipe, one end of the spray pipe communicates with the first solution cavity and the second solution cavity through the tower body, and the first water pump is installed at one end of the spray pipe close to the spray tank.

[0014] Further, the electrochemical pretreater comprises a first body, a mud scraper, a first driving member, an aeration disc, an anode, a cathode, a pulse power supply, a first liquid supply pipe and a first valve body, a liquid inlet end of the first body communicates with the first liquid outlet through the first liquid supply pipe, the first liquid supply pipe is installed with the first valve body, the mud scraper is rotationally installed in the first body, the first driving member communicates with the mud scraper to remove the flocculation on the surface of the solution, the aeration disc is installed at the bottom of the first body, the anode and the cathode are arranged in the first body and communicate with the pulse power supply to pretreat the solution.

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

[0016] Further, the membrane separator comprises a second body, a connecting pipe with the second liquid outlet, a nanofiltration membrane separation assembly, an ultrasonic rod, a second water pump, a liquid outlet pipe with the third liquid outlet, a second liquid delivery pipe and a second valve body, the liquid inlet end of the second body communicates with the liquid outlet end of the electrochemical pretreater through the second liquid delivery pipe, the second valve body is installed on the second liquid delivery pipe, one end of the connecting pipe communicates with the liquid inlet end of the second body, a plurality of nanofiltration membrane separation assemblies are sequentially and spacedly arranged in the second body along the length direction of the connecting pipe, one end of the nanofiltration membrane separation assembly communicates with the connecting pipe, and the other end of each nanofiltration membrane separation assembly sequentially communicates with the liquid outlet pipe, one end of the liquid outlet pipe close to the third liquid outlet is connected with the second water pump, one end of the ultrasonic rod is connected with an ultrasonic generator, and the other end is located at the bottom of the corresponding nanofiltration membrane separation assembly.

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

[0018] Further, the placement direction of the ultrasonic rod is perpendicular to the direction of the solution flowing through the nanofiltration membrane separation assembly.

[0019] Compared with the prior art, the recycling device for separating tail gas halogen has the following beneficial effects:

[0020] The tail gas enters the tower body through the gas inlet, the strong alkali solution and the weak alkali solution in the spray tank flow to different levels of spray assemblies, the two kinds of spray liquids alternately treat the tail gas, the strong alkali solution is used for spraying to make the fluoride precipitate as CaF2, and then the weak alkali solution is used for spraying to sufficiently absorb HCl and HBr, the gas treated by the three-stage spray treatment is discharged from the top gas outlet, and the chlorine / bromine-containing solution is discharged from the first liquid outlet. The chlorine / bromine-containing solution enters the electrochemical pretreatment device, the solution is pretreated to oxidize Br - to generate BrO3 -The radius difference of chlorine ions and bromine ions is caused, the pretreated solution enters a membrane separator, the solution is separated in the membrane separator, the bromine-containing solution intercepted by the membrane is discharged from a second liquid outlet, and the chlorine-containing solution is discharged from a third liquid outlet. The multi-stage treatment system is used to improve the removal rate of the acid gas in the tail gas, the weak alkali solution and the strong alkali solution are sprayed in a cooperative manner, the fluorides are preferentially strengthened and crystallized under the action of calcium ions, the fluorides are removed, and meanwhile, the electrochemical regulation and the membrane separation technology are combined to realize the gradient separation and recovery of fluorine, bromine and chlorine, the operation is simple, the treatment efficiency is high, and it is ensured that the tail gas after treatment meets the environmental protection standard. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a structure schematic diagram of a recovery device for separating tail gas halogens provided by the embodiment of the present application;

[0022] Figure 2 is a structure schematic diagram of a spraying box and an alkali spraying tower provided by the embodiment of the present application;

[0023] Figure 3 is a structure schematic diagram of an electrochemical pretreater provided by the embodiment of the present application;

[0024] Figure 4 is a structure schematic diagram of a membrane separator provided by the embodiment of the present application;

[0025] In the figure, 1 is a spraying box, 11 is a first solution cavity, 12 is a second solution cavity, 2 is an alkali spraying tower, 21 is a tower body, 22 is a spraying assembly, 221 is a first water pump, 222 is a spraying pipe, 223 is a nozzle, 23 is an air inlet, 24 is an air outlet, 25 is a first liquid outlet, 26 is a filter screen, 27 is a filler layer, 3 is an electrochemical pretreater, 31 is a first machine body, 32 is a mud scraping plate, 33 is an aeration disc, 34 is an anode, 35 is a cathode, 36 is a pulse power supply, 37 is a first liquid conveying pipe, 38 is a first valve body, 4 is a membrane separator, 41 is a second liquid outlet, 42 is a third liquid outlet, 43 is a second machine body, 431 is a third cavity, 44 is a connecting pipe, 45 is a nanofiltration membrane separation assembly, 46 is an ultrasonic rod, 47 is a second water pump, 48 is a liquid outlet pipe, 49 is a second liquid conveying pipe, 410 is a second valve body, and 5 is a bubble generator. DETAILED DESCRIPTION

[0026] The specific embodiments of the present application are described in further detail below in combination with the drawings and examples. The following examples are used to illustrate the present application, but are not used to limit the scope of the present application.

[0027] As Figure 1 and Figure 2As shown, the present application provides a recovery device for separating tail gas halogen, which is used for treating tail gas after waste liquid crystal pyrolysis oil gas is combusted in situ, so as to separate halogen in the tail gas in stages. The recovery device comprises a spraying box 1, an alkaline spraying tower 2, an electrochemical pretreater 3 and a membrane separator 4. The spraying box 1 has a first solution cavity 11 and a second solution cavity 12 which are arranged separately, the first solution cavity 11 is used for filling weak alkali solution, and the second solution cavity 12 is used for filling strong alkali solution; the alkaline spraying tower 2 comprises a tower body 21, a spraying assembly 22, an air inlet 23, an air outlet 24, a first liquid outlet 25 and a filter screen 26, the air outlet 24 and the air inlet 23 are arranged in the tower body 21 in sequence and at intervals along the height direction, at least three layers of spraying assemblies 22 are arranged in the tower body 21 in sequence and at intervals along the height direction and are located between the air outlet 24 and the air inlet 23, multi-stage spraying improves the gas-liquid contact area and enhances the absorption efficiency, so that the tail gas can be reacted more fully. Among them, the air 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 the filter screen 26 is arranged at the first liquid outlet 25 to trap CaF2precipitate; the liquid inlet end of the spraying assembly 22 communicates with the first solution cavity 11 and the second solution cavity 12 through the tower body 21, so as to spray the tail gas in the tower body 21 and remove the fluoride therein; the liquid inlet end of the electrochemical pretreater 3 communicates with the first liquid outlet 25, so as to pretreat 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, and the liquid inlet end of the membrane separator 4 communicates with the liquid outlet end of the electrochemical pretreater 3, so as to perform membrane separation treatment on the solution, and use the selective permeability of the membrane to make the bromine-containing solution be discharged through the second liquid outlet 41 and the chlorine-containing solution be discharged through the third liquid outlet 42.

[0028] Based on the above structure, the tail gas enters the tower body 21 through the air inlet 23 first, the strong alkali solution and the weak alkali solution in the spraying box 1 flow to different levels of the spraying assembly 22 respectively, the two kinds of spraying liquids alternately treat the tail gas, the fluoride is precipitated as CaF2by spraying with the strong alkali solution first, and then the weak alkali solution is sprayed to fully absorb HCl and HBr, the gas after three-stage spraying treatment is discharged from the top air outlet 24, and the chlorine / bromine-containing solution is discharged from the first liquid outlet 25. The chlorine / bromine-containing solution enters the electrochemical pretreatment device, the solution is pretreated to oxidize Br - to BrO3 -The radius difference of chlorine and bromine ions is made, and the pretreated solution enters the membrane separator 4. The solution is separated in the membrane separator 4. The bromine-containing solution filtered by the membrane is discharged from the second liquid outlet 41, and the chlorine-containing solution is discharged from the third liquid outlet 42. The present embodiment utilizes a multi-stage treatment system to improve the removal rate of acid gases in the tail gas. The weak base solution and the strong base solution are sprayed in a synergistic manner. Fluoride is preferentially crystallized and removed under the action of calcium ions. At the same time, electrochemical regulation and membrane separation technology are used to realize the gradient separation and recovery of fluorine, bromine and chlorine. The operation is simple, the treatment efficiency is high, and the treated tail gas discharge meets the environmental protection standard.

[0029] It should be noted that the strong base solution and the weak base solution in the spraying box 1 of the present embodiment flow to different levels of spraying assemblies 22, and the two spraying liquids are alternately treated for the tail gas. The strong base solution flows to the spraying assembly 22 located at the bottom, and the weak base solution flows to the spraying assembly 22 located at the upper layer. The tail gas is first contacted with the strong base solution spraying liquid located at the bottom during the rising process. The strong base solution has a pH>12, such as calcium hydroxide (Ca(OH)2) or sodium hydroxide (NaOH) solution. Fluoride (such as HF, NaF, etc.) reacts with calcium ions (Ca 2+ ) under strong alkaline conditions as follows: Ca 2+ +2F-→CaF2↓, to generate insoluble calcium fluoride (CaF2) precipitate, and preferentially remove highly toxic fluoride in the waste gas. Prevent the subsequent absorbent from being saturated by fluoride ions, which affects the absorption of other acid gases. Subsequently, the waste gas is contacted with the weak base solution spraying liquid located at the upper layer. The weak base solution has a pH controlled at about 8-10, such as sodium carbonate (Na2CO3), sodium bicarbonate (NaHCO3) or limestone slurry. Since the waste gas itself contains HCl and HBr, and reacts with the strong base solution to generate HCl and HBr, the following reactions occur in the weak alkaline environment (such as Na2CO3 solution): Na2CO3+2HCl→2NaCl+CO2↑+H2O; Na2CO3+2HBr→2NaBr+CO2↑+H2O, so that HCl and HBr can be effectively neutralized and absorbed.

[0030] Furthermore, it also includes a bubble generator 5, whose outlet end is connected to the inlet end of the spray box 1. In this embodiment, air or other gases are injected into the liquid through the bubble generator 5 to form a large number of tiny bubbles. Then, its outlet end is connected to the spray box 1 so that the liquid containing bubbles is finally sprayed out through the spray assembly 22. When the liquid containing bubbles is sprayed, the bubbles can disperse the liquid into finer droplets or increase the surface area inside the liquid, thereby increasing the contact area between the liquid and the gas in the exhaust gas, thus 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 in this embodiment 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 in this embodiment is a conventional ultrafine bubble generator, and its structure is not specifically limited here.

[0032] Furthermore, the alkaline spray tower 2 also includes a packing layer 27, which is disposed inside the tower body 21 and located above the top spray assembly 22. As the last barrier in the alkaline spray tower 2 treatment process, the packing layer 27 can further absorb and treat the halogen-containing acidic gases that have not been completely absorbed, ensuring that the emitted gases meet environmental protection standards.

[0033] Furthermore, the filler layer 27 includes a skeleton and hollow spheres. The skeleton is filled with multiple hollow spheres, which are usually made of corrosion-resistant materials, such as plastic or ceramic. They have holes on their surface or walls to allow gas to pass through and come into contact with 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 the waste gas that has not been completely treated, so that the waste gas can reach a higher degree of purification and prevent the waste gas from overflowing directly 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 at intervals 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 fine stream at a certain pressure. By arranging the multiple nozzles 223, the liquid can cover the target area more evenly, improving spraying efficiency and effect. One end of the spray pipe 222 passes through the tower body 21 and communicates with the first solution chamber 11 and the second solution chamber 12. The first water pump 221 is used to provide power and is installed at the 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 the present embodiment is an atomizing nozzle or a fan-shaped nozzle. The atomizing nozzle is used to decompose the liquid into very fine droplets, forming a mist, which helps to increase the contact area between the liquid and the gas, thereby improving the mass transfer efficiency. The fan-shaped nozzle is used to spray the liquid in a flat fan-shaped mode, providing a more uniform coverage and ensuring uniform distribution of the liquid throughout the spraying area.

[0036] As shown in Figure 1 and Figure 3 , the electrochemical pretreater 3 includes a first body 31, a mud scraper 32, a first driving member (not shown), an aeration disc 33, an anode 34, a cathode 35, a pulse power supply 36, a first liquid inlet 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. The liquid inlet end of the first body 31 is connected to the first liquid outlet 25 through the first liquid inlet pipe 37, so that the solution can flow into and out of the first body 31. The first valve body 38 is installed at one end of the first liquid inlet pipe 37 near the liquid inlet end of the first body 31, used to control the opening and closing of the first liquid inlet pipe 37, and at the same time control the flow rate of the solution flowing into the first body 31 through the first valve body 38. The mud scraper 32 is rotatably installed in the first body 31, and the first driving member is in communication with the mud scraper 32 to scrape off the flocculation material floated to the surface of the solution, preventing it from re-dissolving or affecting the subsequent treatment effect. The aeration disc 33 is installed at the bottom of the first body 31, and by injecting air or oxygen into the liquid, it promotes the air flotation process, causing the light-weight pollutants (such as flocculation material) to float to the surface, facilitating the removal by the mud scraper 32. The anode 34 and the cathode 35 serve as electrodes for electrochemical reactions, which are installed in the first body 31 and in communication with the pulse power supply 36. The pulse power supply 36 is used to apply voltage in different stages to induce electrochemical reactions for pretreatment of the solution.

[0037] Based on the above structure, the present embodiment adopts two stages to pretreat the solution. The first stage is a low potential stage: at a lower voltage, an electrocoagulation or electroflotation reaction occurs, causing the charged colloidal particles to lose stability and aggregate to form flocculation material; at the same time, the bubbles generated by the aeration disc 33 drive these flocculation materials to float to the liquid surface, and the mud scraper 32 scrapes off these dregs to complete the preliminary purification.

[0038] The second stage is a 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 - , causing Br - to be oxidized to BrO3 - ; in addition, after Br - is oxidized, Cl - reacts with Br -The difference in ionic radius between the two ions is larger, which is conducive to the subsequent removal of the two ions by membrane separation or other physical methods. The present embodiment removes colloidal impurities in stages, removes a large amount of suspended solids and part of the organic matter in advance, reduces the burden on the subsequent treatment system, and changes the ion form to make the subsequent separation process more efficient.

[0039] Preferably, the anode 34 and the cathode 35 of the present embodiment are both porous electrodes, which can increase the effective reaction area of the electrodes and thus improve the efficiency of the electrochemical reaction. Common porous electrode materials include activated carbon, graphite felt, titanium-based coated electrodes (such as Ti / PbO2, Ti / SnO2), etc. The pulse power source 36 of the present embodiment is preferably a unidirectional pulse power source to better control the oxidation or reduction process of the electrodes. Understandably, in the low potential stage, the porous electrode in combination with the unidirectional pulse power source 36 can induce electroflocculation / electroflotation of colloidal particles to improve the efficiency of flocculant generation; in the high potential stage, the porous electrode is Br - A larger reaction area is provided to oxidize BrO3 - ; and the unidirectional pulse prevents unnecessary reduction reactions from interfering with this process.

[0040] It should be noted that the anode 34 and the cathode 35 of the present embodiment can also use flat plate electrodes. The flat plate 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] For example, Figure 1 and Figure 4As shown, the membrane separator 4 comprises a second body 43, a connecting pipe 44 with a second liquid outlet 41, nanofiltration membrane separation assemblies 45, an ultrasonic rod 46, a second water pump 47, a liquid outlet pipe 48 with a third liquid outlet 42, a second liquid delivery pipe 49, and a second valve body 410. The second body 43 is a main container of the entire membrane separation device, and the liquid inlet end thereof is in communication with the liquid outlet end of the electrochemical pretreater 3 through the second liquid delivery pipe 49. One end of the connecting pipe 44 is in communication with the liquid inlet end of the second body 43. The nanofiltration membrane separation assemblies 45 are arranged in the second body 43 in sequence along the length direction of the connecting pipe 44. One end of each nanofiltration membrane separation assembly 45 is in communication with the connecting pipe 44, so that the pretreated solution flows into the nanofiltration membrane separation assemblies 45 along the connecting pipe 44 for membrane separation treatment. The second liquid delivery pipe 49 is provided with the second valve body 410 for controlling the opening and closing of the second liquid delivery pipe 49, and the flow rate of the solution flowing into the connecting pipe 44 is controlled through the second valve body 410. The other end of each nanofiltration membrane separation assembly 45 is in communication with the liquid outlet pipe 48 in sequence. The liquid outlet pipe 48 is connected with the second water pump 47 at the end close to the third liquid outlet 42. The second water pump 47 is used to provide power to draw the separated chlorine-containing solution from the nanofiltration membrane separation assemblies 45 to the liquid outlet pipe 48, and then out of the third liquid outlet 42. The ultrasonic rod 46 is connected with an ultrasonic generator at one end and located at the bottom of the corresponding nanofiltration membrane separation assembly 45 at the other end, so as to generate vibration or cavitation effect through ultrasonic waves to promote the flow of the solution on the membrane surface of the nanofiltration membrane separation assembly 45 and the separation efficiency.

[0042] Based on the above structure, the pretreated solution enters the connecting pipe 44. The solution flows through the plurality of nanofiltration membrane separation assemblies 45, and is separated by using the selective permeability of the membrane. The bromine-containing solution is intercepted by the membrane and then discharged from the second liquid outlet 41. The smaller chlorine molecules can pass through the membrane, so that the chlorine-containing solution is pumped out of the third liquid outlet 42 by the second water pump 47. In this process, the ultrasonic waves generated by the ultrasonic rod 46 can prevent the membrane from being polluted, enhance the mass transfer efficiency, and thus improve the separation effect. In this embodiment, the selective permeability of the nanofiltration membrane separation assemblies 45 to different ions (such as bromide ions and chloride ions) is utilized to realize the effective separation of bromine molecules and chlorine molecules in the solution. It should be noted that the nanofiltration membrane separation assemblies 45 in this embodiment are conventional membrane separation devices, and the structure thereof is not particularly limited herein.

[0043] Further, the second body 43 has a third cavity 431 for containing the nanofiltration membrane separation assembly 45, the ultrasonic rod 46 and the conductive liquid, the bottom end surface of the nanofiltration membrane separation assembly 45 is in contact with the liquid surface of the conductive liquid, and the conductive liquid in the third cavity 431 acts as a bridge to effectively transmit the vibration energy generated by the ultrasonic rod 46 to the membrane surface, 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 part of the nanofiltration membrane separation assembly 45 immersed in the conductive liquid is at least one third of the total length, so that the nanofiltration membrane separation assembly 45 is more fully contacted with the conductive liquid, ensuring that the energy of the ultrasonic waves can fully reach the membrane surface to improve the cleaning efficiency or mass transfer efficiency.

[0044] Further, the ultrasonic rod 46 is placed vertically to the direction in which the solution flows through the nanofiltration membrane separation assembly 45. The solution in this embodiment flows through the nanofiltration membrane separation assembly 45 in a certain direction in turn in the membrane separator 4, and the ultrasonic rod 46 is installed below or near the membrane assembly in a direction perpendicular to the flow direction. For example, the solution flows through the nanofiltration membrane assembly from left to right in the horizontal direction, and the ultrasonic rod 46 is placed vertically, emitting ultrasonic waves from below to above the membrane surface. When the ultrasonic rod 46 is perpendicular to the liquid flow direction, the action range of the ultrasonic waves can more evenly cover the entire membrane surface. The solution will continue to be affected by the ultrasonic waves from the vertical direction during the process of passing through the membrane assembly, increasing the residence time of the liquid in the ultrasonic field, reducing energy waste, and thus improving the treatment effect of the ultrasonic on the solution. If the ultrasonic rod 46 is parallel to the flow direction, the ultrasonic waves may be quickly carried away, resulting in energy not being fully applied to the membrane surface before being carried out with the liquid; the vertical arrangement can make the ultrasonic waves more concentratedly act on the key area (such as the membrane surface).

[0045] The specific steps are as follows:

[0046] S1: The tail gas of the waste liquid crystal pyrolysis oil gas after in-situ combustion enters the alkaline spray tower 2 through the gas inlet 23 first, and the fluorides are precipitated as CaF2 by contacting with the sprayed strong alkali solution. With the rising of the tail gas, it is contacted with the sprayed weak alkali solution to fully absorb HCl and HBr in the tail gas. The gas after three-stage spray treatment is discharged from the top gas outlet 24 after passing through the filler layer 27, and the chlorine / bromine-containing solution is discharged from the first liquid outlet 25. The first liquid outlet 25 is provided with a filter screen 26 to intercept CaF2 precipitates.

[0047] S2: The chlorine / bromine-containing solution enters the electrochemical pretreatment device, is aerated through the bottom aeration disc 33, the anode 34 and the cathode 35 are connected with the pulse power supply 36, the colloidal impurities in the solution are first treated in the low potential stage, the flocculation on the solution surface is scraped off by the mud scraper 32, and then switched to the high potential stage to oxidize Br - BrO3- The radius difference of chlorine and bromine ions is caused, and the pretreated solution is discharged through the second valve body 410.

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

[0049] In summary, the embodiment of the present application provides a recovery device for separating tail gas halogen. The tail gas enters the tower body 21 through the gas inlet 23 first, the strong alkali solution and the weak alkali solution in the spray tank 1 flow to different levels of spray assemblies 22 respectively, the two kinds of spray liquids alternately treat the tail gas, the fluoride is precipitated as CaF2 by spraying the strong alkali solution first, and then the weak alkali solution is sprayed to fully absorb HCl and HBr, the gas after three-stage spray treatment is discharged from the top gas outlet 24, and the chlorine / bromine-containing solution is discharged from the first liquid outlet 25. The chlorine / bromine-containing solution enters the electrochemical pretreatment device, the solution is pretreated to oxidize Br - BrO3 - The radius difference of chlorine and bromine ions is caused, the pretreated solution enters the membrane separator 4, the solution is separated in the membrane separator 4, the bromine-containing solution intercepted by the membrane is discharged from the second liquid outlet 41, and the chlorine-containing solution is discharged from the third liquid outlet 42. The embodiment utilizes a multi-stage treatment system to improve the removal rate of acid gas in the tail gas, the weak alkali solution and the strong alkali solution are sprayed in a synergistic manner, the fluoride is preferentially strengthened and crystallized to remove the fluoride under the action of calcium ions, and meanwhile, the electrochemical regulation and the membrane separation technology are combined to realize the step-by-step separation and recovery of fluorine, bromine and chlorine, so that the operation is simple, the treatment efficiency is high, and it is ensured that the tail gas after treatment meets the environmental protection standard.

[0050] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and replacements without departing from the technical principles of the present application, and these improvements and replacements should also be considered as the protection scope of the present application.

Claims

1. A recovery apparatus for separating tail gas halogens, characterized by, The application relates to a device for treating waste gas, comprising: a spraying box, which is provided with a first solution cavity and a second solution cavity, the first solution cavity is used for filling a weak alkali solution, and the second solution cavity is used for filling a strong alkali solution, and the strong alkali is calcium hydroxide; a basic spraying tower, which comprises a tower body, a spraying assembly, an air inlet, an air outlet, a first liquid outlet and a filter screen, the air outlet and the air inlet are sequentially and spacedly arranged on the tower body along the height direction, at least three layers of the spraying assembly are sequentially and spacedly arranged in the tower body and located between the air outlet and the air inlet, the first liquid outlet is located at the bottom of the tower body, the filter screen is arranged at the first liquid outlet, and the liquid inlet end of the spraying assembly is communicated with the first solution cavity and the second solution cavity through the tower body, so that the waste gas is sprayed in the tower body and the fluoride in the waste gas is removed; an electrochemical pretreater, which is communicated with the first liquid outlet through a liquid inlet end, so that the solution flowing out of the tower body is pretreated, and the radius difference between chloride ions and bromide ions is formed; a membrane separator, which 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 pretreater, so that the solution at the liquid outlet end of the electrochemical pretreater is subjected to membrane separation treatment, 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 apparatus for separating tail gas halogen according to claim 1, characterized by, The device further comprises a bubble generator, and the liquid outlet end of the bubble generator is communicated with the spraying box.

3. The recovery apparatus for separating tail gas halogen according to claim 1, characterized by, The basic spraying tower further comprises a filler layer, which is arranged in the tower body and located above the spraying assembly of the top layer.

4. The recovery apparatus for separating tail gas halogen according to claim 3, characterized by, The filler layer comprises a skeleton and hollow spheres, the skeleton is filled with a plurality of the hollow spheres, and the hollow spheres are filled with quicklime, so as to absorb the waste gas which is not completely treated.

5. The recovery apparatus for separating tail gas halogen according to claim 1, characterized by, The spraying assembly comprises a first water pump, a spraying pipe and a plurality of nozzles which are sequentially and spacedly arranged along the extension direction of the spraying pipe, one end of the spraying pipe is communicated with the first solution cavity and the second solution cavity through the tower body, and the first water pump is installed at one end of the spraying pipe close to the spraying box.

6. The recovery apparatus for separating tail gas halogen according to claim 1, characterized by, The electrochemical pretreater comprises a first body, a mud scraping plate, a first driving member, an aeration disc, an anode, a cathode, a pulse power supply, a first liquid conveying pipe and a first valve body, the liquid inlet end of the first body is communicated with the first liquid outlet through the first liquid conveying pipe, the first liquid conveying pipe is provided with the first valve body, the mud scraping plate is rotationally installed in the first body, the first driving member is communicated with the mud scraping plate to scrape the flocculation which is floated to the surface of the solution, the aeration disc is installed at the bottom of the first body, the anode and the cathode are arranged in the first body and communicated with the pulse power supply, so as to pretreat the solution flowing out of the first liquid outlet.

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

8. The recovery apparatus for separating tail gas halogen according to claim 1, characterized by, The membrane separator comprises a second body, a connecting pipe with the second liquid outlet, a nanofiltration membrane separation assembly, an ultrasonic rod, a second water pump, a liquid outlet pipe with the third liquid outlet, a second liquid inlet pipe and a second valve body, the liquid inlet end of the second body communicates with the liquid outlet end of the electrochemical pretreater through the second liquid inlet pipe, the second liquid inlet pipe is provided with the second valve body, one end of the connecting pipe communicates with the liquid inlet end of the second body, a plurality of nanofiltration membrane separation assemblies are sequentially and spacedly arranged in the second body along the length direction of the connecting pipe, one end of the nanofiltration membrane separation assembly communicates with the connecting pipe, the other end of each nanofiltration membrane separation assembly sequentially communicates with the liquid outlet pipe, one end of the liquid outlet pipe close to the third liquid outlet is connected with the second water pump, one end of the ultrasonic rod is connected with an ultrasonic generator, and the other end is located at the bottom of the corresponding nanofiltration membrane separation assembly.

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

10. The recovery apparatus for separating tail gas halogen according to claim 8, characterized by, The placement direction of the ultrasonic rod is perpendicular to the direction of the solution flowing through the nanofiltration membrane separation assembly.

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