Wet trapping process and equipment for iodine-containing tail gas
By employing a urea-modified sodium hydroxide absorbent and optimizing operating parameters during nuclear fuel reprocessing, efficient capture of gaseous elemental iodine and organic iodine has been achieved. This solves the problems of low efficiency and insufficient stability in existing alkaline absorption methods, providing an efficient and stable iodine capture process and equipment suitable for iodine contamination control in nuclear fuel reprocessing plants.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA INSTITUTE OF ATOMIC ENERGY
- Filing Date
- 2025-12-23
- Publication Date
- 2026-04-17
AI Technical Summary
The existing alkaline absorption method has limited efficiency in capturing organic iodine such as methyl iodine, and suffers from problems such as easy failure of the absorbent, insufficient process stability, and difficult equipment maintenance, resulting in a high risk of radioactive iodine emission pollution during nuclear fuel reprocessing.
Using a sodium hydroxide absorbent containing urea, and through optimization of specific operating parameters, a countercurrent contact absorption reaction between gaseous iodine and methyl iodine is achieved. Combined with the reducing effect of urea, the chemical equilibrium is transformed into an irreversible reaction, thereby improving the collection efficiency. Furthermore, a demisting zone, a spraying zone, and a bubbling zone are set up in the iodine collection tower to optimize conditions such as liquid-gas ratio and temperature.
It achieves a high capture rate of over 98% for gaseous iodine and organic iodine, has good resistance to nitrogen oxide interference, adapts to a wide range of iodine concentrations and gas throughput, simplifies the process flow, reduces the difficulty of equipment modification, and facilitates industrial applications.
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Figure CN121869070A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to exhaust gas treatment technology for nuclear fuel reprocessing, specifically to a wet capture process and equipment for iodine-containing exhaust gas. Background Technology
[0002] During nuclear fuel reprocessing, large amounts of radioactive iodine isotopes (including...) are released. 129 I and 131-135 I, 138- 141 I). Among them. 138 I arrive 141 I has an extremely short half-life, and its potential harm is negligible; while 129 I and 131 I, on the other hand, has an extremely long half-life (approximately 1.57 × 10⁻⁶). 7 With its high specific activity and high concentration (in years), radioactive iodine is one of the most hazardous radioactive isotopes. Direct release into the atmosphere will pollute the environment and seriously threaten human health. The Chernobyl nuclear accident in 1986 and the Fukushima nuclear accident in 2011 both led to a sharp increase in the concentration of radioactive iodine in the surrounding environment, severely impacting the health of local residents and causing tens of thousands of cases of thyroid cancer in adolescents and children. Therefore, in the context of actively developing nuclear energy, the effective treatment of radioactive iodine in spent fuel is particularly important.
[0003] Currently, alkaline absorption is one of the commonly used methods for iodine capture. However, conventional alkaline absorption has limited capture efficiency for organic iodine such as methyl iodine, and suffers from problems such as easy absorption solution failure, insufficient process stability, and difficult equipment maintenance. Therefore, developing an efficient, stable, reliable, and easy-to-maintain iodine capture process and system is of great significance. Summary of the Invention
[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a wet process and equipment for capturing iodine-containing exhaust gas with high capture efficiency, stable operation, and suitability for engineering applications. This process achieves synergistic and efficient removal of both elemental iodine and organic iodine through the synergistic effect of a specific absorbent formulation and optimized operating parameters.
[0005] To achieve the above objectives, in one aspect, the present invention provides a wet capture process for iodine-containing exhaust gas, comprising:
[0006] S1) The absorbent is introduced into the iodine trap and sprayed down from the top;
[0007] S2) The iodine-containing tail gas is introduced into the bottom of the iodine capture tower, so that the tail gas comes into countercurrent contact with the spray absorption liquid in the tower from bottom to top, and the absorption reaction is carried out.
[0008] The absorbent contains urea and sodium hydroxide, and the iodine-containing exhaust gas contains gaseous iodine and methyl iodine.
[0009] Furthermore, in some specific embodiments, in the wet capture process for iodine-containing tail gas as described above, the concentration of sodium hydroxide in the absorbent is 0.05-1 mol / L; and the concentration of urea is 0.05-0.1 mol / L.
[0010] Furthermore, as a preferred embodiment, the concentration of sodium hydroxide in the absorbent is 1 mol / L, and the concentration of urea is 0.05 mol / L.
[0011] Furthermore, in some specific embodiments, in the wet capture process for iodine-containing tail gas as described above, the absorbent liquid in step S1) is sprayed using an atomizing nozzle at a pressure of 118-150 kPa, an atomization angle of 90-100°, an empty tower gas velocity of not less than 0.2 m / s, a critical droplet size of 0.2 mm, and a droplet size of 0.6-0.8 mm inside the tower.
[0012] Furthermore, in some specific embodiments, in the wet capture process for iodine-containing tail gas as described above, the liquid-to-gas ratio of the spray in the iodine capture tower is 28-56 L / m³. 3 46 L / m is preferred 3 .
[0013] Furthermore, in some specific embodiments, in the wet capture process of iodine-containing tail gas as described above, the operating temperature inside the iodine capture tower is 60-80℃, preferably 65℃.
[0014] Furthermore, in some specific embodiments, in the wet capture process of iodine-containing tail gas as described above, the operating pressure inside the iodine capture tower is from slightly negative pressure to atmospheric pressure, preferably atmospheric pressure.
[0015] Furthermore, in some specific embodiments, in the wet capture process for iodine-containing tail gas as described above, the circulation flow rate of the absorbent in the iodine capture tower is 60-180 L / h, preferably 120 L / h.
[0016] Furthermore, in some specific embodiments, in the wet capture process for iodine-containing exhaust gas described above, the total iodine content in the iodine-containing exhaust gas is 100-500 mg / m³. 3 The content of gaseous iodine is greater than 99%.
[0017] Furthermore, in some specific embodiments, the wet capture process for iodine-containing tail gas described above further includes nitrogen oxides in the iodine-containing tail gas. These nitrogen oxides include one or more of nitric oxide, nitrogen dioxide (NO2), dinitrogen trioxide (N2O3), dinitrogen tetroxide (N2O4), and dinitrogen pentoxide (N2O5), with a nitrogen oxide concentration of 300-700 mg / m³. 3 .
[0018] Furthermore, in some specific embodiments, in the wet capture process for iodine-containing tail gas as described above, the absorbent liquid after the reaction is filtered and then recycled.
[0019] On the other hand, the present invention further provides a wet capture device for iodine-containing tail gas to realize the above-mentioned process, including an iodine capture tower, which is divided into a demisting zone, a spraying zone, an absorption zone and a bubbling zone from top to bottom. A demister is provided in the demisting zone, an atomizing nozzle is provided in the spraying zone, and the atomizing nozzle is connected to an absorbent tank via a liquid supply pipeline. A bubbling device is provided in the bubbling zone and is connected to a tail gas pipeline. An absorbent containing urea and sodium hydroxide is stored in the absorbent tank. The tail gas pipeline is connected to an iodine generator, and the iodine-containing tail gas contains gaseous elemental iodine and methyl iodine.
[0020] Furthermore, in some specific embodiments, in the iodine-containing exhaust gas wet capture device described above, the atomizing nozzle is preferably a hollow cone nozzle.
[0021] Furthermore, in some specific embodiments, in the iodine-containing tail gas wet capture device described above, the liquid holding height in the bubbling zone inside the iodine capture tower is 0.5-0.6m.
[0022] Furthermore, in some specific embodiments, in the iodine-containing tail gas wet capture device described above, the bottom of the iodine capture tower is connected to a waste liquid tank and an absorbent reuse filter, the absorbent reuse filter is connected to the absorbent tank, and the absorbent is recycled after filtration treatment.
[0023] Furthermore, in some specific embodiments, in the iodine-containing exhaust gas wet capture device described above, nitrogen oxides are also introduced into the exhaust gas pipeline. The nitrogen oxides include one or more of nitric oxide, nitrogen dioxide (NO2), dinitrogen trioxide (N2O3), dinitrogen tetroxide (N2O4), and dinitrogen pentoxide (N2O5).
[0024] Furthermore, in some specific embodiments, the iodine-containing exhaust gas wet capture device described above, wherein the top of the iodine capture tower is connected to an exhaust gas treatment tank.
[0025] Furthermore, in some specific embodiments, the iodine-containing tail gas wet capture device described above has an outlet tail gas sampling port at the top of the iodine capture tower and a reaction liquid sampling port at the bottom of the iodine capture tower.
[0026] The beneficial effects of this invention are as follows:
[0027] This invention provides a wet capture process for iodine-containing exhaust gas. By introducing urea as a reducing agent into the sodium hydroxide absorbent, the reaction between iodine and alkali (3I₂ + 6NaOH) is effectively disrupted. The chemical equilibrium of 5NaI + NaIO3 + 3H2O transforms the originally reversible process into an irreversible reaction, greatly enhancing the gas-liquid absorption process. This results in an iodine capture efficiency consistently above 98%, superior to the traditional soda ash absorption method. Furthermore, this process exhibits excellent tolerance to nitrogen oxides (NO2) in iodine-containing gases. Even under NO2 concentrations as high as 700 mg / m³, it maintains an iodine capture rate of over 97%, demonstrating superior resistance to competitive absorption and ensuring stable operation of the process under complex gas composition conditions.
[0028] Furthermore, the process of this invention exhibits wide adaptability to both the total iodine concentration in the inlet gas (0.1-0.5 g / m³) and the gas throughput (i.e., a liquid-to-gas ratio within the range of 28-56 L / m³). It achieves efficient capture of both high- and low-concentration iodine-containing waste gas, providing good flexibility for practical industrial operations. It can synergistically treat multiple forms of iodine, demonstrating excellent capture effects on both gaseous molecular iodine (I₂) and trace amounts of organic iodine (such as methyl iodine). By optimizing process conditions, synergistic and efficient removal of different forms of iodine compounds is achieved in a single process, simplifying the process flow.
[0029] This invention can improve performance simply by optimizing the absorbent formulation and key process parameters (temperature, liquid-to-gas ratio, etc.), without requiring complex modifications to existing absorber equipment. It is easy to promote and apply to existing devices and has significant engineering practical value and economic benefits. Attached Figure Description
[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0031] Figure 1 This is a schematic diagram of the wet capture process for iodine-containing tail gas in a specific embodiment of the present invention. Detailed Implementation
[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0033] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.
[0034] The terms “comprising”, “including”, etc., as used herein indicate the presence of the steps, features, operations, components, ingredients, etc., but do not preclude the addition of one or more other steps, features, operations, components, ingredients, etc.
[0035] This invention provides a wet capture process for iodine-containing exhaust gas, comprising:
[0036] S1) The absorbent is introduced into the iodine trap and sprayed down from the top;
[0037] S2) Iodine-containing tail gas is introduced into the bottom of the iodine collection tower, and the tail gas is made to rise by a bubbling device and come into countercurrent contact with the spray absorption liquid in the tower to carry out the absorption reaction.
[0038] The absorbent includes urea and sodium hydroxide, and the iodine-containing exhaust gas includes gaseous iodine and trace amounts of methyl iodine.
[0039] This invention uses urea-containing alkaline solution as the absorbent and, through a multi-stage reaction mechanism, significantly improves the capture efficiency of elemental iodine and methyl iodine, achieving an iodine capture rate of over 99%, superior to traditional alkaline washing processes. Furthermore, by systematically optimizing operating parameters (liquid-to-gas ratio, temperature, alkaline concentration, etc.), the stability of the process under long-term operation is ensured. The disclosed process is applicable to the treatment of iodine-containing radioactive waste gas in nuclear fuel reprocessing plants, providing a reliable technical solution and design basis for iodine pollution control in commercial nuclear power plants and large-scale reprocessing plants.
[0040] In some embodiments of the present invention, the sodium hydroxide concentration in the absorbent is 0.05-1.0 mol / L, preferably 1.0 mol / L; the urea concentration is 0.05-0.1 mol / L, preferably 0.05 mol / L; the spraying treatment in S1) is carried out using an atomizing nozzle installed in a spray tower, preferably a hollow cone nozzle, with a pressure of 118-150 kPa, an atomization angle of 90-100°, an empty tower gas velocity of not less than 0.2 m / s, a critical droplet size of 0.2 mm, and a droplet size of 0.6-0.8 mm in the tower. In the above embodiments, by adopting the preferred spray angle, uniform spraying can be achieved; the preferred hollow cone nozzle for atomization treatment provides good atomization effect, which is conducive to the full contact and reaction between the absorbent droplets and the iodine-rich gas.
[0041] The liquid-to-gas ratio operating conditions for the iodine trap are 28-56 L / m³. 3 46 L / m is preferred 3 The operating temperature of the iodine collection tower is 60-80℃, preferably 65℃; the liquid holding height in the bubbling zone of the iodine collection tower is 0.5-0.6m; the operating pressure inside the tower is from slightly negative pressure to atmospheric pressure, preferably atmospheric pressure; the alkaline solution circulation flow rate (i.e., spray density) of the iodine collection tower is 60-180 L / h, preferably 120 L / h. In the above implementation scheme, by selecting an absorbent solution of preferred concentration and the spray liquid-to-gas ratio, temperature, and operating pressure in the iodine collection tower, the absorbent droplets can fully react with the iodine-rich gas to capture the iodine element therein.
[0042] In some embodiments of the present invention, the total iodine content in the iodine-containing exhaust gas in S2) is 100-500 mg / m³. 3 500 mg / m 3 The iodine-containing exhaust gas contains gaseous elemental iodine and methyl iodine. It is produced by mixing gaseous elemental iodine and trace amounts of methyl iodine in a mixing tank. The gaseous elemental iodine is generated by an inorganic iodine generator at a concentration of 127-841 mg / m³. 3 Preferred concentration: 841 mg / m 3 Methyl iodine is generated by an organic iodine generator. In the above embodiment, the content of gaseous iodine is 99.5%, and the content of methyl iodine is 0.5%.
[0043] In some embodiments of the present invention, the iodine-containing exhaust gas in S2) further contains nitrogen oxides, which include one or more of nitric oxide, nitrogen dioxide (NO2), dinitrogen trioxide (N2O3), dinitrogen tetroxide (N2O4), and dinitrogen pentoxide (N2O5), and the content of nitrogen oxides is 300-700 mg / m³. 3 300 mg / m 3 The concentration of NO2 was 0-700 mg / m³.3 700 mg / m 3 In the above embodiments, the iodine-containing gas contains a large number of toxic and harmful impurity elements. The method of the present invention can not only capture gaseous iodine in the iodine-containing gas, but also capture nitrogen oxides, reduce the content of impurity elements, and reduce environmental pollution. Sodium hydroxide can react with nitrogen oxides to produce sodium nitrate and sodium nitrite, and urea can react with nitrogen oxides to produce nitrogen gas, thereby significantly reducing the nitrogen oxide content and reducing air pollution.
[0044] In some embodiments of the present invention, the treatment flow rate of the iodine-containing tail gas in S2) is 180 L / h. In the above embodiments, by selecting a preferred treatment flow rate of the iodine-containing tail gas, the liquid content can be increased, which is beneficial to the absorption of gaseous iodine.
[0045] The average diameter of the droplets was tested using Easyviewer400 to measure the droplet size, which allows for testing and analysis of the atomization characteristics under different nozzles. The software's built-in algorithm yielded the size of each droplet and performed statistical analysis.
[0046] The method for testing the concentration of gaseous iodine is as follows: a soap film flow meter and a stopwatch are used to calibrate the flow rate of the mixed gas, thereby indirectly determining the concentration of gaseous iodine.
[0047] The method for testing the concentration of iodine in the liquid phase is as follows: The concentration of gaseous iodine before entering the absorption tower, i.e., the total iodine content, can be determined using the difference method. Then, the concentration of gaseous iodine after exiting the absorption tower and the concentration of free inorganic iodide ions (I₂O₃) in the absorbent are used. - and IO3 - The concentration of molecular iodine in the solution can be obtained by subtracting the concentration of iodine from the concentration of iodine.
[0048] The concentration of gaseous iodine and organic iodine in the exhaust gas was tested by online gas chromatography analysis using a GC-9890 instrument.
[0049] The method for testing the concentration of iodide ions in the inlet liquid of the iodine trap is as follows: the concentration is tested using a UV-Vis spectrometer, model UV1901PCS.
[0050] The process system flow of the present invention is as follows: Figure 1As shown, the specific process employs a wet capture device for iodine-containing tail gas, including: an iodine capture tower, an absorbent tank, an inorganic iodine generator, an organic iodine generator, a mixing tank, a waste liquid tank, an absorbent reuse filter, and a tail gas treatment tank. The iodine capture tower is divided into a demisting zone, a spraying zone, an absorption zone, and a bubbling zone from top to bottom. A demister is installed in the demisting zone, and atomizing nozzles are installed in the spraying zone. These nozzles are connected to the absorbent tank via a supply pipeline. The absorbent is sprayed from the top of the iodine capture tower through the atomizing nozzles and comes into countercurrent contact with the rising tail gas in the absorption zone for absorption. The bubbling zone is equipped with a bubbling device connected to the mixing tank via a tail gas pipeline. The mixing tank is connected to both the inorganic and organic iodine generators. Gaseous elemental iodine and trace amounts of methyl iodine are mixed in the mixing tank to form iodine-containing tail gas. The absorbent tank stores an absorbent containing urea and sodium hydroxide. The bottom of the iodine capture tower is connected to a waste liquid tank and an absorbent reuse filter. The absorbent reuse filter is connected to the absorbent tank, and the absorbent is recycled after filtration. The top of the iodine capture tower is connected to a tail gas treatment tank. Additionally, the tail gas pipeline is connected to a nitrogen oxide gas generator, which sends the nitrogen oxide gas into the bubbling zone of the iodine capture tower via a gas heater. An outlet tail gas sampling port is located at the top of the iodine capture tower, and a reaction liquid sampling port is located at the bottom. Gas chromatography can be used for online sampling and analysis of the concentration of elemental iodine and organic iodine in the outlet tail gas, and ultraviolet-visible spectrophotometer can be used to analyze the iodide ion concentration in the liquid sample.
[0051] The present invention will be further described below through examples. Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods.
[0052] Example 1
[0053] S1) Prepare an absorbent solution containing 1.0 mol / L sodium hydroxide and 0.05 mol / L urea. The absorbent solution is stored in an absorbent solution tank and introduced into the iodine collection tower by a high-pressure pump, then sprayed down from the top through atomizing nozzles. By adjusting the circulation pump frequency, the liquid-to-gas ratio of the spray is made to reach 46 L / m³. 3 And maintain the operating temperature of the iodine capture tower at 65℃.
[0054] S2) Iodine-containing tail gas with a total iodine content of 500 mg / m³ (of which the content of gaseous iodine is 99.5% and the content of methyl iodine is 0.5%) and a nitrogen oxide concentration of 500 mg / m³ is introduced into the iodine capture tower from the bottom. The tail gas is raised by a bubbling device and comes into countercurrent contact with the spray absorption liquid in the tower to carry out the absorption reaction. The total gas flow rate is controlled at 180 L / h and the liquid holding height in the bubbling zone in the tower is controlled at 0.5 m.
[0055] After the S3 system has been running stably for 1 hour, samples were taken from the outlet tail gas and inlet liquid of the iodine capture tower at the outlet and inlet sampling ports, respectively. A 5 mm diameter stainless steel pipe was connected to both the inlet and outlet of the iodine capture tower and heated. Due to the slight negative pressure at the top of the tower, a pump was used to extract the iodine from the tail gas, resulting in tail gas 1. A liquid sample was collected from the bottom of the iodine capture tower. The manual valve was opened for 20 seconds to discharge the liquid. After the circulating liquid discharge stabilized, a 300 mL alkali collection bottle was used to collect the circulating alkali solution, resulting in liquid sample 1.
[0056] Example 2
[0057] The method of Example 1 was used, except that the absorbent in S1) was a 0.2 mol / L sodium hydroxide solution, and tail gas 2 and liquid sample 2 were obtained.
[0058] Example 3
[0059] The method of Example 1 was used, except that the absorbent in S1) was a 0.5 mol / L sodium hydroxide solution, and tail gas 3 and liquid sample 3 were obtained.
[0060] Example 4
[0061] The method of Example 1 was used, except that the absorbent in S1) was a 2 mol / L sodium hydroxide solution, and tail gas 4 and liquid sample 4 were obtained.
[0062] Example 5
[0063] The method of Example 1 was used, except that the absorbent in S1) was a 3 mol / L sodium hydroxide solution, and tail gas 5 and liquid sample 5 were obtained.
[0064] Test case
[0065] The concentrations of elemental iodine and organic iodine in the exhaust gas were analyzed by online gas chromatography, and the concentration of iodide ions in the liquid sample was analyzed by ultraviolet-visible spectrophotometer. The iodine capture rate was calculated using the following formula.
[0066] Iodine capture rate = (Imported iodine concentration - Exported iodine concentration) / Imported iodine concentration
[0067] Table 1 compares the iodine capture rates in the five examples.
[0068] Example number 1 2 3 4 5 Iodine capture rate 0.991 0.844 0.898 0.930 0.958
[0069] A comparison of the data from Examples 1 and 2-5 shows that, in Example 1, when the preferred absorbent solution of the present invention is used with a sodium hydroxide concentration of 1 mol / L, a urea concentration of 0.05 mol / L, and a sodium hydroxide to urea concentration ratio of 20:1, the iodine capture efficiency is high, with an iodine capture rate greater than 90%. The method of the present invention is simple to operate, has high capture efficiency, and is suitable for large-scale industrial applications.
[0070] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. Thus, the invention also intends to include such variations and adaptations if they fall within the scope of the claims and their equivalents.
[0071] The above embodiments are merely illustrative examples of the present invention. The present invention may also be implemented in other specific ways or forms without departing from its spirit or essential characteristics. Therefore, the described embodiments should be considered illustrative rather than limiting in any respect. The scope of protection of the present invention should be defined by the claims, and any variations equivalent to the intent and scope of the claims should also be included within the scope of the present invention.
Claims
1. A wet capture process for iodine-containing exhaust gas, characterized in that, include: S1) The absorbent is introduced into the iodine trap and sprayed down from the top; S2) The iodine-containing tail gas is introduced into the bottom of the iodine capture tower, so that the tail gas comes into countercurrent contact with the spray absorption liquid in the tower from bottom to top, and the absorption reaction is carried out. The absorbent contains urea and sodium hydroxide, and the iodine-containing exhaust gas contains gaseous iodine and methyl iodine.
2. The wet capture process for iodine-containing tail gas as described in claim 1, characterized in that, The concentration of sodium hydroxide in the absorbent is 0.05-1 mol / L; the concentration of urea is 0.05-0.1 mol / L.
3. The wet capture process for iodine-containing tail gas as described in claim 1, characterized in that, The concentration of sodium hydroxide in the absorbent is 1 mol / L, and the concentration of urea is 0.05 mol / L.
4. The wet capture process for iodine-containing tail gas as described in claim 1, characterized in that, The absorbent liquid described in step S1) is sprayed using an atomizing nozzle at a pressure of 118-150 kPa, an atomization angle of 90-100°, an empty tower gas velocity of not less than 0.2 m / s, a critical droplet size of 0.2 mm, and a droplet size of 0.6-0.8 mm inside the tower.
5. The wet capture process for iodine-containing tail gas as described in claim 1, characterized in that, The liquid-to-gas ratio of the spray in the iodine capture tower is 28-56 L / m³. 3 .
6. The wet capture process for iodine-containing tail gas as described in claim 1, characterized in that, The operating temperature inside the iodine capture tower is 60-80℃.
7. The wet capture process for iodine-containing tail gas as described in claim 1, characterized in that, The operating pressure inside the iodine capture tower is from slightly negative pressure to atmospheric pressure.
8. The wet capture process for iodine-containing tail gas as described in claim 1, characterized in that, The absorption liquid circulation flow rate of the iodine capture tower is 60-180 L / h.
9. The wet capture process for iodine-containing tail gas as described in claim 1, characterized in that, The total iodine content in the iodine-containing exhaust gas is 100-500 mg / m³. 3 Of which, the content of gaseous iodine is greater than 99%.
10. The wet capture process for iodine-containing tail gas as described in claim 1, characterized in that, The iodine-containing exhaust gas also contains nitrogen oxides, including one or more of nitric oxide, nitrogen dioxide, dinitrogen trioxide, dinitrogen tetroxide, and dinitrogen pentoxide, with a concentration of 300-700 mg / m³. 3 .
11. The wet capture process for iodine-containing tail gas as described in claim 1, characterized in that, The absorbent solution after the reaction in step S2) is filtered and then recycled.
12. A wet capture device for iodine-containing tail gas in implementing the process described in any one of claims 1-11, comprising an iodine capture tower, characterized in that, The iodine collection tower is divided into a demisting zone, a spraying zone, an absorption zone, and a bubbling zone from top to bottom. A demister is installed in the demisting zone, and an atomizing nozzle is installed in the spraying zone. The atomizing nozzle is connected to the absorption liquid tank through a liquid supply pipeline. A bubbling device is installed in the bubbling zone and is connected to the exhaust gas pipeline. The absorption liquid tank stores an absorption liquid containing urea and sodium hydroxide. The exhaust gas pipeline is connected to an iodine generator, and the iodine-containing exhaust gas contains gaseous elemental iodine and methyl iodine.
13. The wet capture device for iodine-containing exhaust gas as described in claim 12, characterized in that, The atomizing nozzle is preferably a hollow cone nozzle.
14. The wet capture device for iodine-containing exhaust gas as described in claim 12, characterized in that, The liquid holding height in the bubbling zone of the iodine capture tower is 0.5-0.6m.
15. The wet capture device for iodine-containing exhaust gas as described in claim 12, characterized in that, The bottom of the iodine capture tower is connected to a waste liquid tank and an absorbent reuse filter. The absorbent reuse filter is connected to the absorbent tank, and the absorbent is recycled after filtration.
16. The wet capture device for iodine-containing exhaust gas as described in claim 12, characterized in that, Nitrogen oxides are also introduced into the exhaust pipe, including one or more of nitric oxide, nitrogen dioxide, dinitrogen trioxide, dinitrogen tetroxide, and dinitrogen pentoxide.
17. The wet capture device for iodine-containing exhaust gas as described in claim 12, characterized in that, The top of the iodine capture tower is connected to a tail gas treatment tank.
18. The wet capture device for iodine-containing exhaust gas as described in claim 12, characterized in that, An outlet exhaust gas sampling port is provided at the top of the iodine capture tower, and a reaction liquid sampling port is provided at the bottom of the iodine capture tower.