CN114512254B - Method for trapping gaseous iodine - Google Patents
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- CN114512254B CN114512254B CN202210102944.4A CN202210102944A CN114512254B CN 114512254 B CN114512254 B CN 114512254B CN 202210102944 A CN202210102944 A CN 202210102944A CN 114512254 B CN114512254 B CN 114512254B
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- 239000011630 iodine Substances 0.000 title claims abstract description 142
- 229910052740 iodine Inorganic materials 0.000 title claims abstract description 142
- ZCYVEMRRCGMTRW-UHFFFAOYSA-N 7553-56-2 Chemical compound [I] ZCYVEMRRCGMTRW-UHFFFAOYSA-N 0.000 title claims abstract description 141
- 238000000034 method Methods 0.000 title claims abstract description 68
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 123
- 239000002250 absorbent Substances 0.000 claims abstract description 67
- 230000002745 absorbent Effects 0.000 claims abstract description 67
- 239000007921 spray Substances 0.000 claims abstract description 55
- 239000007788 liquid Substances 0.000 claims abstract description 43
- INQOMBQAUSQDDS-UHFFFAOYSA-N iodomethane Chemical compound IC INQOMBQAUSQDDS-UHFFFAOYSA-N 0.000 claims abstract description 17
- 238000000889 atomisation Methods 0.000 claims abstract description 15
- PNDPGZBMCMUPRI-UHFFFAOYSA-N iodine Chemical compound II PNDPGZBMCMUPRI-UHFFFAOYSA-N 0.000 claims abstract description 8
- 239000007789 gas Substances 0.000 claims description 115
- 239000000243 solution Substances 0.000 claims description 62
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims description 41
- 239000007864 aqueous solution Substances 0.000 claims description 13
- 239000003513 alkali Substances 0.000 claims description 12
- 238000005507 spraying Methods 0.000 claims description 9
- LZDSILRDTDCIQT-UHFFFAOYSA-N dinitrogen trioxide Chemical compound [O-][N+](=O)N=O LZDSILRDTDCIQT-UHFFFAOYSA-N 0.000 claims description 8
- ZWWCURLKEXEFQT-UHFFFAOYSA-N dinitrogen pentaoxide Chemical compound [O-][N+](=O)O[N+]([O-])=O ZWWCURLKEXEFQT-UHFFFAOYSA-N 0.000 claims description 6
- WFPZPJSADLPSON-UHFFFAOYSA-N dinitrogen tetraoxide Chemical compound [O-][N+](=O)[N+]([O-])=O WFPZPJSADLPSON-UHFFFAOYSA-N 0.000 claims description 6
- 239000002915 spent fuel radioactive waste Substances 0.000 claims description 6
- 238000007599 discharging Methods 0.000 claims description 5
- 238000000746 purification Methods 0.000 claims description 5
- MGWGWNFMUOTEHG-UHFFFAOYSA-N 4-(3,5-dimethylphenyl)-1,3-thiazol-2-amine Chemical compound CC1=CC(C)=CC(C=2N=C(N)SC=2)=C1 MGWGWNFMUOTEHG-UHFFFAOYSA-N 0.000 claims description 4
- JCXJVPUVTGWSNB-UHFFFAOYSA-N nitrogen dioxide Inorganic materials O=[N]=O JCXJVPUVTGWSNB-UHFFFAOYSA-N 0.000 claims description 4
- 239000003518 caustics Substances 0.000 claims 2
- 239000000126 substance Substances 0.000 abstract description 12
- 230000002285 radioactive effect Effects 0.000 abstract description 10
- 238000010521 absorption reaction Methods 0.000 abstract description 4
- 238000003912 environmental pollution Methods 0.000 abstract description 4
- 238000006243 chemical reaction Methods 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 238000012546 transfer Methods 0.000 description 5
- 239000002699 waste material Substances 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- 238000001514 detection method Methods 0.000 description 3
- 238000002386 leaching Methods 0.000 description 3
- NALMPLUMOWIVJC-UHFFFAOYSA-N n,n,4-trimethylbenzeneamine oxide Chemical compound CC1=CC=C([N+](C)(C)[O-])C=C1 NALMPLUMOWIVJC-UHFFFAOYSA-N 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 239000011697 sodium iodate Substances 0.000 description 3
- 229940032753 sodium iodate Drugs 0.000 description 3
- 235000015281 sodium iodate Nutrition 0.000 description 3
- 238000005406 washing Methods 0.000 description 3
- 239000002912 waste gas Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000004255 ion exchange chromatography Methods 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- PKAUVIXBZJUYRV-UHFFFAOYSA-N methane;hydroiodide Chemical compound C.I PKAUVIXBZJUYRV-UHFFFAOYSA-N 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000003758 nuclear fuel Substances 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 description 2
- LPXPTNMVRIOKMN-UHFFFAOYSA-M sodium nitrite Chemical compound [Na+].[O-]N=O LPXPTNMVRIOKMN-UHFFFAOYSA-M 0.000 description 2
- 238000002798 spectrophotometry method Methods 0.000 description 2
- BDHFUVZGWQCTTF-UHFFFAOYSA-M sulfonate Chemical compound [O-]S(=O)=O BDHFUVZGWQCTTF-UHFFFAOYSA-M 0.000 description 2
- NWZSZGALRFJKBT-KNIFDHDWSA-N (2s)-2,6-diaminohexanoic acid;(2s)-2-hydroxybutanedioic acid Chemical compound OC(=O)[C@@H](O)CC(O)=O.NCCCC[C@H](N)C(O)=O NWZSZGALRFJKBT-KNIFDHDWSA-N 0.000 description 1
- 229920002430 Fibre-reinforced plastic Polymers 0.000 description 1
- 208000024770 Thyroid neoplasm Diseases 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000011151 fibre-reinforced plastic Substances 0.000 description 1
- IKDUDTNKRLTJSI-UHFFFAOYSA-N hydrazine monohydrate Substances O.NN IKDUDTNKRLTJSI-UHFFFAOYSA-N 0.000 description 1
- XMBWDFGMSWQBCA-UHFFFAOYSA-M iodide Chemical compound [I-] XMBWDFGMSWQBCA-UHFFFAOYSA-M 0.000 description 1
- 229940006461 iodide ion Drugs 0.000 description 1
- -1 iodine ions Chemical class 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000002572 peristaltic effect Effects 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 235000010344 sodium nitrate Nutrition 0.000 description 1
- 239000004317 sodium nitrate Substances 0.000 description 1
- 235000010288 sodium nitrite Nutrition 0.000 description 1
- 238000007619 statistical method Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 201000002510 thyroid cancer Diseases 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 238000000870 ultraviolet spectroscopy Methods 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
- G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
- G21F9/02—Treating gases
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
- G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
- G21F9/007—Recovery of isotopes from radioactive waste, e.g. fission products
Abstract
The present disclosure relates to a method of capturing gaseous iodine, the method comprising: s1, introducing an absorbent solution into a spray tower for atomization treatment to obtain absorbent atomized liquid drops; s2, introducing iodine-enriched gas into the spray tower, and enabling the iodine-enriched gas to be in countercurrent contact with the atomized liquid drops of the absorbent from bottom to top to obtain mixed gas and iodine-enriched solution; wherein the absorbent solution comprises sodium hydroxide and/or N 2 H 4 ·H 2 O, the iodine-enriched gas comprises elemental iodine and methyl iodide. The method can effectively collect gaseous iodine simple substance and organic iodine by adopting a spray absorption method, and reduce radioactive iodine emission and environmental pollution.
Description
Technical Field
The present disclosure relates to the technical field of nuclear fuel post-treatment process exhaust gas treatment, and in particular, to a method of trapping gaseous iodine.
Background
During the nuclear fuel post-treatment process, a large amount of radioactive iodine isotopes are released 129,131-135,138-141 I) A. The invention relates to a method for producing a fibre-reinforced plastic composite Wherein the method comprises the steps of 138-141 I has extremely short half-life and causes negligible harm 129 I and 131 i are each extremely long in half-life (1.57×10 7 Years) and radioactive iodine isotopes with higher specific activity, which are the most serious hazards, are directly discharged into the air to pollute the environment and seriously damage human health. The nuclear accident of Chernobeli in 1986 and the nuclear accident of Fudao in Japan in 2011 cause the concentration of radioactive iodine in the surrounding environment to increase exponentially, which poses serious threat to the physical health of local residents, causing the thousands of teenagers and children to suffer from thyroid cancer. Therefore, in the age background of the great development of nuclear energy, the radioactive iodine treatment in the spent fuel is particularly important.
The foreign spent fuel post-treatment factory researches the purification treatment method of iodine to be more mature, the La Hague post-treatment facility in France and the Windscale, THORP facility in England both use alkaline washing to capture gaseous iodine in the solution, the waste gas can remove iodine simple substances in the waste gas through 1-2mol/L sodium hydroxide solution, however, organic iodine is also contained in the waste gas, and the alkali liquor washing has poor removal effect on the organic iodine, so the removal efficiency of the alkali liquor washing is generally not more than 90 percent.
Disclosure of Invention
The object of the present disclosure is to provide a method for trapping gaseous iodine, which can effectively trap gaseous iodine by adopting a spray absorption method, improve the trapping efficiency of elemental iodine and organic iodine, and reduce the emission of radioactive iodine.
The present disclosure provides a method of capturing gaseous iodine, the method comprising: s1, introducing an absorbent solution into a spray tower for atomization treatment to obtain absorbent atomized liquid drops; s2, introducing iodine-enriched gas into the spray tower, and enabling the iodine-enriched gas to be in countercurrent contact with the atomized liquid drops of the absorbent from bottom to top to obtain mixed gas and iodine-enriched solution; wherein the absorbent solution comprises sodium hydroxide and/or N 2 H 4 ·H 2 O, the iodine-enriched gas comprises elemental iodine and methyl iodide.
Optionally, the concentration of sodium hydroxide in the absorbent solution in S1 is 0.05 to 0.5mol/L, N 2 H 4 ·H 2 The concentration of O is 0.05-0.5 mol/L; preferably, the absorbent solution comprises sodium hydroxide and N 2 H 4 ·H 2 O, the sodium hydroxide and the N 2 H 4 ·H 2 The concentration ratio of O is (1-10): 1, a step of; the temperature of the absorbent solution is 60 to 80 ℃, preferably 70 to 80 ℃.
Optionally, the atomization treatment in S1 is performed by using an atomization nozzle provided in a spray tower; the aperture of the atomizing nozzle is 0.5-0.7 mm, and the pressure is 5 multiplied by 10 4 ～10×10 4 Pa, the spraying angle is 100-115 degrees; wherein the average diameter of the atomized liquid drops of the absorbent is 60-150 mu m; preferably, the atomizing nozzle is a hydraulic spiral atomizing nozzle.
Optionally, the temperature of the spray tower in S1 is 55-70 ℃, and the height of the spray tower is 0.5-1.0 m, preferably 0.6-0.8 m; the height-diameter ratio of the spray tower is (5-15): 1, preferably (8 to 12): 1, a step of; wherein the spray tower comprises two spray layers, and the height difference of the two spray layers is 5-20 mm, preferably 10-20 mm.
Optionally, the mass concentration of iodine element in the iodine-enriched gas in S2 is 1-500 mg/m 3 Preferably 50 to 200mg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the The mass of iodine element in the methyl iodide is below 1 percent based on the total mass of iodine element in the iodine-enriched gas.
Optionally, the iodine-enriched gas in S2 further comprises nitrogen oxides and/or radionuclides; the nitrogen oxides include nitrogen monoxide, nitrogen dioxide (NO 2 ) Dinitrogen trioxide (N) 2 O 3 ) Dinitrogen tetroxide (N) 2 O 4 ) And dinitrogen pentoxide (N) 2 O 5 ) One or more of the following; the radionuclide comprises 3 H、 84 Br、 85 Kr and 133 one or more of Xe.
Optionally, the iodine-enriched gas in the S2 is generated in a spent fuel post-treatment process, and the temperature of the iodine-enriched gas is 80-100 ℃, preferably 90-100 ℃; the flow ratio of the absorbent solution to the iodine-enriched gas is (5-80): 1, preferably (5 to 20): 1.
optionally, the method further comprises purifying the mixed gas obtained in S2, and the step of purifying includes: and demisting the mixed gas, discharging the demisted mixed gas from a gas outlet at the top of the spray tower, and purifying the demisted mixed gas by entering a sodium hydroxide aqueous solution through a gas inlet of an alkali solution tank.
Optionally, the demisting is performed by using a demister, the demister is a wire mesh demister, and the demisting efficiency of the wire mesh demister is more than 99%.
Optionally, the concentration of the sodium hydroxide aqueous solution in the alkali solution tank is 0.5-3 mol/L, the gas inlet of the alkali solution tank is positioned below the liquid level of the sodium hydroxide aqueous solution, and the height of the gas inlet from the liquid level is 0.8-1.2 m.
Through the technical scheme, the method for trapping gaseous iodine can obtain the absorbent liquid drops with proper diameters by adopting a spray absorption method, so that iodine-rich gas and the absorbent liquid drops are fully contacted to generate chemical reaction and gas-liquid mass transfer, the gaseous iodine is effectively trapped, the trapping efficiency of organic iodine is improved, and the emission of radioactive iodine is reduced; the absorbent solution with smaller concentration is used, so that the usage amount of the absorbent solution can be reduced, the waste liquid treatment cost and the factory maintenance cost are reduced, and the equipment loss and the environmental pollution are reduced.
Additional features and advantages of the present disclosure will be set forth in the detailed description which follows.
Detailed Description
The following describes specific embodiments of the present disclosure in detail. It should be understood that the detailed description and specific examples, while indicating and illustrating the disclosure, are not intended to limit the disclosure.
The present disclosure provides a method of capturing gaseous iodine, the method comprising: s1, introducing an absorbent solution into a spray tower for atomization treatment to obtain absorbent atomized liquid drops; s2, introducing iodine-enriched gas into the spray tower, and enabling the iodine-enriched gas to be in countercurrent contact with the atomized liquid drops of the absorbent from bottom to top to obtain mixed gas and iodine-enriched solution; wherein the absorbent solution comprises sodium hydroxide and/or N 2 H 4 ·H 2 O, the iodine-enriched gas comprises elemental iodine and methyl iodide.
According to the method provided by the disclosure, the absorbent solution is subjected to atomization treatment, so that absorbent droplets with proper diameters can be obtained, the absorbent droplets are fully contacted with iodine-rich gas to generate chemical reaction and gas-liquid mass transfer, gaseous iodine is effectively removed, and the trapping efficiency of organic iodine is improved; wherein sodium hydroxide reacts with iodine simple substance to generate iodide ion and sodium iodate, N 2 H 4 ·H 2 O can further react with the iodine simple substance and sodium iodate to generate iodine ions, so that the trapping efficiency of the absorbent solution on iodine elements is improved. According to the method disclosed by the invention, the gaseous iodine can be effectively trapped only by adopting the absorbent solution with proper concentration without introducing strong oxidizing gas, so that the emission of radioactive iodine and the usage amount of the absorbent are reduced, and the waste liquid treatment cost is reduced; the method disclosed by the invention is simple to operate, high in trapping efficiency, less in damage degree to equipment and suitable for industrial large-scale application.
In one embodiment of the present disclosure, S1, wherein the concentration of sodium hydroxide in the absorbent solution is 0.05 to 0.5mol/L, and the concentration of N is 2 H 4 ·H 2 The concentration of O is 0.05-0.5 mol/L; preferably, the absorbent solution comprises sodium hydroxide and N 2 H 4 ·H 2 O, the sodium hydroxide and the N 2 H 4 ·H 2 The concentration ratio of O is (1-10): 1, a step of; further, the concentration of the sodium hydroxide is 0.1 to 0.25mol/L, and the concentration of the N is 2 H 4 ·H 2 The concentration of O is 0.05-0.1 mol/L; the temperature of the absorbent solution is 60 to 80 ℃, preferably 70 to 80 ℃. In the above embodiment, by selecting an absorbent solution of a preferred concentration and temperature, the absorbent droplets can be sufficiently reacted with the iodine-rich gas to trap iodine element therein.
In one embodiment of the present disclosure, the atomizing treatment in S1 is performed using an atomizing nozzle provided in a spray tower; the aperture of the atomizing nozzle is 0.5-0.7 mm, and the pressure is 5 multiplied by 10 4 ～10×10 4 Pa, the spraying angle is 100-115 degrees; wherein the average diameter of the atomized liquid drops of the absorbent atomized by the atomizing nozzle is 60-150 mu m; preferably, the atomizing nozzle is a hydraulic spiral atomizing nozzle. In the above embodiment, uniform spraying can be achieved by adopting a preferable spraying angle; the optimized spiral atomizing nozzle is adopted for atomizing treatment, so that the atomizing effect is good, the absorbent atomized liquid drops with the average diameter of 60-150 mu m can be obtained, and the full contact reaction of the absorbent liquid drops and iodine-enriched gas is facilitated.
In one embodiment of the present disclosure, the temperature of the spray tower in S1 is 55 to 70 ℃, and the height of the spray tower is 0.5 to 1.0m, preferably 0.6 to 0.8m; the height-diameter ratio of the spray tower is (5-15): 1, preferably (8 to 12): 1, a step of; wherein the spray tower comprises two spray layers, and the height difference of the two spray layers is 5-20 mm, preferably 10-20 mm. In a preferred embodiment, a spiral atomizing nozzle is provided on the spray layer; further, the number of the spiral atomizing nozzles is five, three spiral atomizing nozzles are arranged on the upper spraying layer, and two spiral atomizing nozzles are arranged on the lower spraying layer. In the embodiment, the spray tower with preferable height and height-diameter ratio is selected, so that atomized absorbent atomized liquid drops can be contacted with the iodine-enriched tail gas from bottom to top for a long time, chemical reaction and gas-liquid mass transfer of the iodine-enriched tail gas are carried out on the surfaces of the absorbent liquid drops, removal and purification of iodine elements in the iodine-enriched gas are facilitated, and the iodine trapping efficiency is improved.
In one embodiment of the present disclosure, the mass concentration of iodine element in the iodine-rich gas in S2 is 1-500 mg/m 3 Preferably 50 to 200mg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the The mass of the iodine element in the methyl iodide is 1% or less, for example, 0.01 to 1% based on the total mass of the iodine element in the iodine-rich gas. In the above embodiment, the iodine-rich tail gas contains inorganic iodine and organic iodine, and the mass of the inorganic iodine may be 90% or more, and the mass of the organic iodine may be 0.01 to 1%, based on the total mass of iodine elements, wherein the organic iodine may be methyl iodide.
In one embodiment of the present disclosure, the iodine-enriched gas in S2 further comprises nitrogen oxides and/or radionuclides; the nitrogen oxides include nitrogen monoxide, nitrogen dioxide (NO 2 ) Dinitrogen trioxide (N) 2 O 3 ) Dinitrogen tetroxide (N) 2 O 4 ) And dinitrogen pentoxide (N) 2 O 5 ) One or more of the following; the radionuclide comprises 3 H、 84 Br、 85 Kr and 133 one or more of Xe. In the above embodiment, the iodine-enriched gas contains a large amount of toxic and harmful impurity elements, and the method of the present disclosure not only can trap gaseous iodine in the iodine-enriched gas, but also can trap nitrogen oxides, reduce the content of the impurity elements, and reduce environmental pollution; wherein sodium hydroxide can react with nitrogen oxides to generate sodium nitrate and sodium nitrite, and hydrazine hydrate can react with nitrogen oxides to generate nitrogen, so that the content of nitrogen oxides is obviously reduced, and the pollution to the atmosphere is reduced.
In one embodiment of the disclosure, the iodine-enriched gas in S2 is generated in a spent fuel post-treatment process, and the temperature of the iodine-enriched gas is 80-100 ℃, preferably 90-100 ℃; the flow ratio of the absorbent solution to the iodine-enriched gas is (5-80): 1, preferably (5 to 20): 1. in the above embodiment, the temperature of the iodine-enriched tail gas is greater than 77 ℃ and not more than 100 ℃, for example, may be 80 to 100 ℃, so as to prevent the iodine simple substance in the iodine-enriched tail gas from sublimating and precipitating during transportation.
In one embodiment of the present disclosure, the method further includes performing a purifying process on the mixed gas obtained in S2, the purifying process including: demisting the mixed gas, discharging the demisted mixed gas from a gas outlet at the top of the spray tower, and purifying the demisted mixed gas by entering a sodium hydroxide aqueous solution through a gas inlet of an alkali solution tank; in a preferred embodiment, the purified tail gas is detected, the tail gas passing the detection is discharged into the atmosphere, and the tail gas passing the detection is returned to the spray tower for continuous treatment. In the above embodiment, the mixed gas is purified to remove the iodine simple substance and sodium iodate remained in the mixed gas, so as to obtain the tail gas with less impurity content and less pollution, which is beneficial to being discharged into the atmosphere.
In one embodiment of the present disclosure, the demisting is performed with a demister, the demister is a wire mesh demister, and the demisting efficiency of the wire mesh demister is 99% or more. In the above embodiment, by adopting the preferred demister, the iodine-rich solution carried in the mixed gas can be removed, so that the pure mixed gas enters the alkali solution tank for purification, the pollution of the sodium hydroxide aqueous solution is avoided, and the waste liquid treatment capacity is reduced.
In one embodiment of the disclosure, the concentration of the sodium hydroxide aqueous solution in the alkali solution tank is 0.5-3 mol/L, the gas inlet of the alkali solution tank is positioned below the liquid level of the sodium hydroxide aqueous solution, and the height of the gas inlet from the liquid level is 0.8-1.2 m. In the above embodiment, by introducing the mixed gas into the sodium hydroxide aqueous solution having a preferable concentration and a preferable height, the iodine element remaining in the mixed gas can be sufficiently absorbed, and the pollution of the iodine element to the environment can be reduced.
According to the method provided by the disclosure, the absorbent solution is subjected to atomization treatment, so that absorbent droplets with proper diameters can be obtained, the absorbent droplets are fully contacted with iodine-rich gas to generate chemical reaction and gas-liquid mass transfer, gaseous iodine is effectively removed and purified, nitrogen oxides can be captured, and the content of impurity elements is reduced; according to the method disclosed by the invention, the gaseous iodine can be effectively trapped by adopting a smaller-concentration absorbent solution without introducing strong oxidizing gas, the trapping efficiency of the organic iodine is improved, the emission of radioactive iodine and the use amount of the absorbent are reduced, and the waste liquid treatment cost and the factory operation cost are reduced; the method has the advantages of simple operation, high trapping efficiency and small damage degree to equipment, and is suitable for industrialized large-scale application.
The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited thereto, and experimental methods used in the following examples and comparative examples are conventional methods unless otherwise specified.
Spiral atomizing nozzles were purchased from Shanghai Fizepine spray systems Co., ltd;
the average diameter of the droplets was measured by: taking an original photo in a test by adopting a particle size measurement system, selecting a region with a better effect and clearer liquid drops for processing, marking the region by using software, obtaining the particle size of each liquid drop by using a software built-in algorithm, and carrying out statistical analysis; the particle size measurement system consists of a high-speed digital camera and a computer data acquisition and analysis system;
the method for testing the concentration of the gaseous iodine simple substance in the tail gas comprises the following steps: testing by adopting ion chromatography according to the method specified by national standard GBZ T160.85-2007, wherein the model of the instrument is ICS5000;
the method for testing the concentration of gaseous methyl iodide in the tail gas comprises the following steps: the method adopts a spectrophotometer and uses 1, 2-naphthoquinone-4-sodium sulfonate spectrophotometry to test, and the model of the instrument is a Laibetay ultraviolet visible spectrophotometer UV1900.
Example 1
S1, feeding an absorbent solution with the temperature of 60 ℃ and the flow rate of 100mL from the top of a spray tower by a peristaltic pump, and forming absorbent atomized liquid drops with the average diameter of 80 mu m by a spiral atomization nozzle arranged in the spray tower; wherein the absorbent solution consists of sodium hydroxide solution with the concentration of 0.1mol/L and N with the concentration of 0.05mol/L 2 H 4 ·H 2 O composition, spray towerThe temperature is 60 ℃, the height is 0.7m, and the diameter is 0.08m; the spray tower is provided with two spray layers, the height of the upper spray layer is 0.55m, 3 spiral atomizing nozzles are arranged, the height of the lower spray layer is 0.45m, and 2 spiral atomizing nozzles are arranged; the diameter of the spiral atomizing nozzle is 0.635mm, and the pressure is 6 multiplied by 10 4 Pa, the spraying angle is 105 degrees;
s2, iodine-enriched gas with the temperature of 90 ℃ generated in the spent fuel post-treatment process (the mass concentration of iodine element in the iodine-enriched gas is 100 mg/m) 3 The mass of iodine in methyl iodide is 0.5 percent based on the total mass of iodine in iodine-enriched gas; wherein the iodine enriched gas further comprises nitric oxide, nitrogen dioxide (NO 2 ) Dinitrogen trioxide (N) 2 O 3 )、 3 H、 84 Br、 85 Kr and 133 xe) is introduced from the bottom of the spray tower, and is in countercurrent contact with the atomized liquid drops of the absorbent sprayed by the spiral atomization nozzle from bottom to top, chemical reaction and gas-liquid mass transfer occur on the surfaces of the liquid drops, mixed gas and iodine-enriched solution are obtained, and the iodine-enriched solution is discharged from the bottom of the tower and enters a waste liquid storage tank; wherein the flow rate of the iodine-enriched gas is 20mL/min;
s3, removing entrained liquid drops from mixed gas through a wire mesh demister, discharging the mixed gas from a gas outlet at the top of a spray tower (the demisting efficiency of the wire mesh demister is 99.5%), purifying the mixed gas by entering sodium hydroxide aqueous solution through a gas inlet of an alkali solution tank to obtain tail gas 1, discharging the tail gas 1 into the atmosphere after the tail gas 1 enters a detection device to be detected to be qualified, and returning the unqualified mixture to the spray tower for continuous treatment (the concentration of the sodium hydroxide aqueous solution is 2mol/L, the gas inlet of the alkali solution tank is positioned below the liquid level of the sodium hydroxide aqueous solution, and the height from the liquid level of the sodium hydroxide aqueous solution is 1 m).
Example 2
The procedure of example 1 was used, with the only difference that: the absorbent solution in S1 is sodium hydroxide solution with the concentration of 0.1mol/L, and tail gas 2 is obtained.
Example 3
The procedure of example 1 was used, with the only difference that: the absorbent solution in S1 was N at 0.05mol/L 2 H 4 ·H 2 O, obtaining tail gas 3.
Example 4
The procedure of example 1 was used, with the only difference that: the concentration of the sodium hydroxide solution in the S1 absorbent solution is 0.01mol/L, and tail gas 4 is obtained.
Example 5
The procedure of example 1 was used, with the only difference that: the concentration of the sodium hydroxide solution in the S1 absorbent solution is 2mol/L, and tail gas 5 is obtained.
Example 6
The procedure of example 1 was used, with the only difference that: the diameter of the spiral atomizing nozzle in S1 is 2mm, and the pressure is 3X 10 4 Pa, the average diameter of the atomized droplets of the absorbent after atomization is about 500. Mu.m, giving a tail gas 6.
Example 7
The procedure of example 1 was used, with the only difference that: s1, replacing the spiral atomizing nozzle with a standard fan-shaped nozzle, wherein the aperture of the standard fan-shaped nozzle is 0.5mm, and the pressure is 6 multiplied by 10 4 Pa, the average diameter of the atomized droplets of the absorbent after atomization is 2000. Mu.m, giving a tail gas 7.
Comparative example 1
The procedure of example 1 was used, with the only difference that: and directly leaching the iodine-enriched gas after the absorbent solution is input from the top of the spray tower without adopting a spiral atomizing nozzle, wherein the average diameter of leached liquid drops is 5000 mu m, and obtaining comparative tail gas 1.
Test case
Analyzing the concentration of the iodine simple substance in the tail gas by ion chromatography according to a method specified by national standard GBZ T160.85-2007, analyzing the concentration of the iodine methane in the tail gas by adopting a 1, 2-naphthoquinone-4-sodium sulfonate spectrophotometry, and respectively calculating the trapping efficiency of the gaseous iodine simple substance and the iodine methane;
the trapping efficiency of the gaseous elemental iodine= (mass concentration of elemental iodine in the elemental iodine-mass concentration of elemental iodine in the tail gas)/mass concentration of elemental iodine in the elemental iodine-rich gas;
the trapping efficiency of gaseous methyl iodide= (mass concentration of methyl iodide element in iodine-rich gas-mass concentration of methyl iodide element in tail gas)/mass concentration of methyl iodide element in iodine-rich gas.
TABLE 1
As can be seen from comparison of the data of comparative example 1 and example 1, comparative example 1 does not adopt the technical scheme of the atomization treatment of the disclosure, but uses leaching liquid drops with an average diameter of 5000 μm for leaching, the obtained tail gas has relatively high iodine element content, relatively low iodine capturing efficiency, the capturing efficiency of gaseous iodine simple substance is less than 75%, and the capturing efficiency of gaseous methyl iodide is less than 18%.
As can be seen from a comparison of the data of example 1 and examples 2-5, the preferred absorbent solutions for example 1 using the present disclosure have a concentration of sodium hydroxide of 0.05 to 0.5mol/L, N 2 H 4 ·H 2 The concentration of O is 0.05-0.5 mol/L, and the absorbent solution contains sodium hydroxide and N 2 H 4 ·H 2 O, sodium hydroxide and N 2 H 4 ·H 2 The concentration ratio of O is (1-10): 1, the iodine trapping efficiency is higher, the trapping efficiency of iodine simple substance is more than 99%, and the trapping efficiency of methyl iodide is more than 39%; the concentration of sodium hydroxide adopted in the embodiment 1 is smaller, and the sodium hydroxide remained in the spray head is not easy to crystallize after the trapping process is finished, so that the spray head and the pipeline are prevented from being blocked, the maintenance cost of a factory is reduced, the equipment loss is reduced, and the method is suitable for industrial large-scale application; as can be seen from a comparison of the data in example 1 and example 6, the preferred spiral atomizing nozzles for example 1 using the present disclosure have a bore diameter of 0.5 to 0.7mm and a pressure of 5X 10 4 ～10×10 4 In the technical scheme of Pa, the trapping efficiency of iodine simple substance and methyl iodide is high; as can be seen from comparison of the data in example 1 and example 7, in the case of the technical scheme of the atomization treatment by using the spiral atomization nozzle according to the preferred embodiment of the present disclosure, the obtained atomized droplets have smaller average diameter and more uniform distribution (the droplet diameter is basically within the average diameter range), the iodine capturing efficiency is higher, and the iodine element in the tail gas containsThe amount is relatively small. The method disclosed by the invention is simple to operate, high in trapping efficiency, capable of effectively trapping gaseous iodine by adopting a spray absorption method, reducing radioactive iodine emission and environmental pollution, and suitable for industrial large-scale application.
The preferred embodiments of the present disclosure have been described in detail above, but the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solutions of the present disclosure within the scope of the technical concept of the present disclosure, and all the simple modifications belong to the protection scope of the present disclosure.
In addition, the specific features described in the foregoing embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, the present disclosure does not further describe various possible combinations.
Moreover, any combination between the various embodiments of the present disclosure is possible as long as it does not depart from the spirit of the present disclosure, which should also be construed as the disclosure of the present disclosure.
Claims (15)
1. A method of capturing gaseous iodine, the method comprising:
s1, introducing an absorbent solution into a spray tower for atomization treatment to obtain absorbent atomized liquid drops; the average diameter of the atomized liquid drops of the absorbent is 60-150 mu m;
s2, introducing iodine-enriched gas into the spray tower, and enabling the iodine-enriched gas to be in countercurrent contact with the atomized liquid drops of the absorbent from bottom to top to obtain mixed gas and iodine-enriched solution;
wherein the absorbent solution comprises sodium hydroxide and/or N 2 H 4 ·H 2 O, the iodine-enriched gas comprises elemental iodine and methyl iodide.
2. The method according to claim 1, wherein the concentration of sodium hydroxide in the absorbent solution in S1 is 0.05 to 0.5mol/L, N 2 H 4 ·H 2 The concentration of O is 0.05-0.5 mol/L; the saidThe temperature of the absorbent solution is 60-80 ℃.
3. The method of claim 2, wherein the absorbent solution comprises sodium hydroxide and N 2 H 4 ·H 2 O, the sodium hydroxide and the N 2 H 4 ·H 2 The concentration ratio of O is (1-10): 1, a step of; the temperature of the absorbent solution is 70-80 ℃.
4. The method of claim 1, wherein the atomizing in S1 is performed using an atomizing nozzle provided in a spray tower; the aperture of the atomizing nozzle is 0.5-0.7 mm, and the pressure is 5 multiplied by 10 4 ～10×10 4 Pa, the spraying angle is 100-115 degrees.
5. The method of claim 4, wherein the atomizing nozzle is a hydraulic helical atomizing nozzle.
6. The method according to claim 1, wherein the temperature of the spray tower in S1 is 55 to 70 ℃, the height of the spray tower is 0.5 to 1.0m, and the aspect ratio of the spray tower is (5 to 15): 1, a step of;
the spray tower comprises two spray layers, and the height difference of the two spray layers is 5-20 mm.
7. The method according to claim 6, wherein the height of the spray tower in S1 is 0.6 to 0.8m, and the aspect ratio of the spray tower is (8 to 12): 1, a step of; the height difference of the two spraying layers is 10-20 mm.
8. The method according to claim 1, wherein the mass concentration of iodine element in the iodine-rich gas in S2 is 1-500 mg/m 3 The mass of iodine element in the methyl iodide is below 1 percent based on the total mass of iodine element in the iodine-enriched gas.
9. The method according to claim 8, wherein the mass concentration of iodine element in the iodine-rich gas in S2 is 50-200 mg/m 3 。
10. The method of claim 1, wherein the iodine-enriched gas in S2 further comprises nitrogen oxides and/or radionuclides; the nitrogen oxides include nitrogen monoxide, nitrogen dioxide (NO 2 ) Dinitrogen trioxide (N) 2 O 3 ) Dinitrogen tetroxide (N) 2 O 4 ) And dinitrogen pentoxide (N) 2 O 5 ) One or more of the following; the radionuclide comprises 3 H、 84 Br、 85 Kr and 133 one or more of Xe.
11. The method of claim 1, wherein the iodine-enriched gas is generated in the post-treatment process of spent fuel in S2, the temperature of the iodine-enriched gas is 80-100 ℃, and the flow ratio of the absorbent solution to the iodine-enriched gas is (5-80): 1.
12. the method of claim 11, wherein the temperature of the iodine-enriched gas is between 90 and 100 ℃, and the flow ratio of the absorbent solution to the iodine-enriched gas is between (5 and 20): 1.
13. the method according to claim 1, further comprising subjecting the mixed gas obtained in S2 to a purification treatment, the step of the purification treatment comprising: and demisting the mixed gas, discharging the demisted mixed gas from a gas outlet at the top of the spray tower, and purifying the demisted mixed gas by entering a sodium hydroxide aqueous solution through a gas inlet of an alkali solution tank.
14. The method of claim 13, wherein the demisting is performed using a demister, the demister being a wire demister having a demisting efficiency of 99% or more.
15. The method according to claim 13, characterized in that the concentration of the aqueous sodium hydroxide solution in the caustic tank is 0.5-3 mol/L, the gas inlet of the caustic tank is located below the liquid level of the aqueous sodium hydroxide solution, and the height of the gas inlet from the liquid level is 0.8-1.2 m.
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