CN114512254A - Method for trapping gaseous iodine - Google Patents
Method for trapping gaseous iodine Download PDFInfo
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- CN114512254A CN114512254A CN202210102944.4A CN202210102944A CN114512254A CN 114512254 A CN114512254 A CN 114512254A CN 202210102944 A CN202210102944 A CN 202210102944A CN 114512254 A CN114512254 A CN 114512254A
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- iodine
- gas
- absorbent
- sodium hydroxide
- spray tower
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- ZCYVEMRRCGMTRW-UHFFFAOYSA-N 7553-56-2 Chemical compound [I] ZCYVEMRRCGMTRW-UHFFFAOYSA-N 0.000 title claims abstract description 137
- 239000011630 iodine Substances 0.000 title claims abstract description 137
- 229910052740 iodine Inorganic materials 0.000 title claims abstract description 137
- 238000000034 method Methods 0.000 title claims abstract description 59
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 135
- 239000002250 absorbent Substances 0.000 claims abstract description 65
- 230000002745 absorbent Effects 0.000 claims abstract description 65
- 239000007921 spray Substances 0.000 claims abstract description 52
- 239000007788 liquid Substances 0.000 claims abstract description 46
- INQOMBQAUSQDDS-UHFFFAOYSA-N iodomethane Chemical compound IC INQOMBQAUSQDDS-UHFFFAOYSA-N 0.000 claims abstract description 19
- OAKJQQAXSVQMHS-UHFFFAOYSA-N Hydrazine Chemical compound NN OAKJQQAXSVQMHS-UHFFFAOYSA-N 0.000 claims abstract description 15
- 238000000889 atomisation Methods 0.000 claims abstract description 12
- PNDPGZBMCMUPRI-UHFFFAOYSA-N iodine Chemical compound II PNDPGZBMCMUPRI-UHFFFAOYSA-N 0.000 claims abstract description 10
- 239000007789 gas Substances 0.000 claims description 113
- 239000000243 solution Substances 0.000 claims description 48
- 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 14
- 238000000746 purification Methods 0.000 claims description 11
- 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 8
- LZDSILRDTDCIQT-UHFFFAOYSA-N dinitrogen trioxide Chemical compound [O-][N+](=O)N=O LZDSILRDTDCIQT-UHFFFAOYSA-N 0.000 claims description 8
- 238000005507 spraying Methods 0.000 claims description 8
- 239000003513 alkali Substances 0.000 claims description 7
- 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
- JCXJVPUVTGWSNB-UHFFFAOYSA-N nitrogen dioxide Inorganic materials O=[N]=O JCXJVPUVTGWSNB-UHFFFAOYSA-N 0.000 claims description 4
- 239000000126 substance Substances 0.000 abstract description 11
- 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
- 230000000052 comparative effect Effects 0.000 description 5
- 238000001514 detection method Methods 0.000 description 5
- 238000012360 testing method Methods 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
- 238000002386 leaching Methods 0.000 description 4
- 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
- 235000015281 sodium iodate Nutrition 0.000 description 3
- 229940032753 sodium iodate Drugs 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
- 230000009286 beneficial effect Effects 0.000 description 2
- -1 iodide ions Chemical class 0.000 description 2
- 238000004255 ion exchange chromatography Methods 0.000 description 2
- 238000012423 maintenance Methods 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
- 208000024770 Thyroid neoplasm Diseases 0.000 description 1
- OKJPEAGHQZHRQV-UHFFFAOYSA-N Triiodomethane Natural products IC(I)I OKJPEAGHQZHRQV-UHFFFAOYSA-N 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- IKDUDTNKRLTJSI-UHFFFAOYSA-N hydrazine monohydrate Substances O.NN IKDUDTNKRLTJSI-UHFFFAOYSA-N 0.000 description 1
- XMBWDFGMSWQBCA-RNFDNDRNSA-M iodine-131(1-) Chemical compound [131I-] XMBWDFGMSWQBCA-RNFDNDRNSA-M 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000002572 peristaltic effect Effects 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000012958 reprocessing 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
- 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
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
- Treating Waste Gases (AREA)
- Gas Separation By Absorption (AREA)
Abstract
The present disclosure relates to a method of capturing gaseous iodine, the method comprising: s1, introducing the absorbent solution into a spray tower for atomization treatment to obtain absorbent atomized liquid drops; s2, introducing iodine-rich gas into the spray tower, and enabling the iodine-rich gas to be in countercurrent contact with the atomized liquid drops of the absorbent from bottom to top to obtain mixed gas and an iodine-rich solution; wherein the absorbent solution comprises sodium hydroxide and/or N2H4·H2O, the iodine-rich gas comprises elemental iodine and methyl iodide. The method adopts a spray absorption method, can effectively trap gaseous iodine simple substances and organic iodine, and reduces radioactive iodine emission and environmental pollution.
Description
Technical Field
The disclosure relates to the technical field of exhaust treatment of a nuclear fuel post-treatment process, in particular to a method for trapping gaseous iodine.
Background
A large amount of radioiodine is released during the reprocessing of nuclear fuels (129,131-135,138-141I) In that respect Wherein138-141The half-life of I is extremely short, causing negligible harm129I and131i is extremely long in half-life (1.57X 10)7Year) and high specific activity, and the radioactive iodine isotope becomes the most serious harmful radioactive iodine isotope, and the direct discharge into the air causes pollution to the environment and seriously harms human health. The chernobilex nuclear accident in 1986 and the fukushima nuclear accident in 2011 japan exponentially increase the radioactive iodine concentration in the surrounding environment, and pose a serious threat to the physical health of local residents, so that tens of thousands of teenagers and children suffer from thyroid cancer. Therefore, under the background of the era of vigorously developing nuclear energy, the treatment of radioactive iodine in spent fuel becomes particularly important.
The research on the purification treatment method of iodine by foreign spent fuel post-treatment plants is mature, the La Hague post-treatment facility in France and the Windscale and THORP facilities in England both use alkaline washing to capture gaseous iodine in a dissolving solution, the iodine in waste gas can be removed by passing the waste gas through 1-2mol/L sodium hydroxide solution, however, organic iodine exists in the waste gas, the removal effect of the alkali washing on the organic iodine is poor, and therefore the removal efficiency of the alkali washing is generally not more than 90%.
Disclosure of Invention
The purpose of the present disclosure is to provide a method for trapping gaseous iodine, which can effectively trap gaseous iodine, improve the trapping efficiency of iodine elementary substance and organic iodine, and reduce radioactive iodine emission by adopting a spray absorption method.
The present disclosure provides a method of capturing gaseous iodine, the method comprising: s1, introducing the absorbent solution into a spray tower for atomization treatment to obtain absorbent atomized liquid drops; s2, introducing iodine-rich gas into the spray tower, and enabling the iodine-rich gas to be in countercurrent contact with the atomized liquid drops of the absorbent from bottom to top to obtain mixed gas and an iodine-rich solution; wherein the absorbent solution comprises sodium hydroxide and/or N2H4·H2O, the iodine-rich gas comprises elemental iodine and methyl iodide.
Optionally, the concentration of sodium hydroxide in the absorbent solution in S1 is 0.05-0.5 mol/L, and N is2H4·H2The concentration of O is 0.05-0.5 mol/L; preferably, the absorbent solution comprises sodium hydroxide and N2H4·H2O, the sodium hydroxide and the N2H4·H2The concentration ratio of O is (1-10): 1; the temperature of the absorbent solution is 60 ℃ to 80 ℃, and 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 104～10×104Pa, the spraying angle is 100-115 degrees; wherein the average diameter of the atomized droplets of the absorbent is 60-150 μm; 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 (8-12): 1; 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-rich gas in S2 is 1-500 mg/m3Preferably 50 to 200mg/m3(ii) a The mass of the iodine element in the methyl iodide is less than 1% based on the total mass of the iodine element in the iodine-rich gas.
Optionally, the iodine-rich gas in S2 further comprises nitrogen oxides and/or radionuclides; the nitrogen oxides include nitric oxide and nitrogen dioxide (NO)2) Dinitrogen trioxide (N)2O3) Dinitrogen tetroxide (N)2O4) And dinitrogen pentoxide (N)2O5) One or more of the above; the radionuclide comprises3H、84Br、85Kr and133one or more Xe.
Optionally, the iodine-rich gas generated in the post-treatment process of the spent fuel in S2 is at a temperature of 80-100 ℃, preferably 90-100 ℃; the flow ratio of the absorbent solution to the iodine-rich gas is (5-80): 1, preferably (5-20): 1.
optionally, the method further includes performing a purification process on the mixed gas obtained in S2, where the purification process includes: demisting the mixed gas, discharging the demisted mixed gas from a gas outlet at the top of the spray tower, and introducing the demisted mixed gas into a sodium hydroxide aqueous solution through a gas inlet of an alkali liquor tank for purification.
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 lye tank is 0.5-3 mol/L, a gas inlet of the lye 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.
According to 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 is fully contacted with the absorbent liquid drops 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 using 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 disclosure will be set forth in the detailed description which follows.
Detailed Description
The following describes in detail specific embodiments of the present disclosure. It should be understood that the detailed description and specific examples, while indicating the present disclosure, are given by way of illustration and explanation only, not limitation.
The present disclosure provides a method of capturing gaseous iodine, the method comprising: s1, introducing the absorbent solution into a spray tower for atomization treatment to obtain absorbent atomized liquid drops; s2, introducing iodine-rich gas into the spray tower, and enabling the iodine-rich gas to be in countercurrent contact with the atomized liquid drops of the absorbent from bottom to top to obtain mixed gas and an iodine-rich solution; wherein the absorbent solution comprises sodium hydroxide and/or N2H4·H2O, the iodine-rich gas comprises elemental iodine and methyl iodide.
According to the method provided by the disclosure, the absorbent liquid drop with a proper diameter can be obtained by atomizing the absorbent solution, so that the absorbent liquid drop is fully contacted with the iodine-rich gas to generate chemical reaction and gas-liquid mass transfer, the gaseous iodine is effectively removed, and the capture efficiency of the organic iodine is improved; wherein the sodium hydroxide reacts with the iodine simple substance to generate iodide ions and sodium iodate, N2H4·H2O reacts with iodine simple substance and sodium iodate to generate iodide ions, so that the capture efficiency of the absorbent solution on the iodine element is improved. The method disclosed by the invention can effectively trap gaseous iodine without introducing strong oxidizing gas and only by adopting an absorbent solution with proper concentration, and reduce radioactive iodine emission and the usage amount of the absorbent, thereby reducing the waste liquid treatment cost; the method disclosed by the invention is simple to operate, high in trapping efficiency, low in damage degree to equipment and suitable for industrial large-scale application.
In this disclosureIn one embodiment of the invention, the concentration of sodium hydroxide in the absorbent solution in S1 is 0.05-0.5 mol/L, and the N is2H4·H2The concentration of O is 0.05-0.5 mol/L; preferably, the absorbent solution comprises sodium hydroxide and N2H4·H2O, the sodium hydroxide and the N2H4·H2The concentration ratio of O is (1-10): 1; further, the concentration of the sodium hydroxide is 0.1-0.25 mol/L, and the N is2H4·H2The concentration of O is 0.05-0.1 mol/L; the temperature of the absorbent solution is 60 ℃ to 80 ℃, and preferably 70 ℃ to 80 ℃. In the above embodiment, by selecting the absorbent solution with a preferred concentration and temperature, the absorbent droplets can be sufficiently reacted with the iodine-rich gas to trap elemental iodine therein.
In one embodiment of the present disclosure, the atomization process in S1 is performed 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 104～10×104Pa, the spraying angle is 100-115 degrees; wherein the average diameter of atomized droplets of the absorbent atomized by the atomizing nozzle is 60-150 μm; preferably, the atomizing nozzle is a hydraulic spiral atomizing nozzle. In the above embodiment, by adopting a preferable spray angle, uniform spraying can be achieved; the optimized spiral atomizing nozzle is adopted for atomizing, the atomizing effect is good, the atomized absorbent liquid drops with the average diameter of 60-150 mu m can be obtained, and the sufficient contact reaction of the absorbent liquid drops and the iodine-rich 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 0.8 m; the height-diameter ratio of the spray tower is (5-15): 1, preferably (8-12): 1; 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 arranged on the spraying layer; furthermore, 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 above embodiment, by selecting the spray tower with the preferred height-to-diameter ratio, the atomized liquid droplets of the absorbent can be in contact with the iodine-rich tail gas from bottom to top for a sufficiently long time, so that the iodine-rich tail gas can perform a chemical reaction and gas-liquid mass transfer on the surfaces of the liquid droplets of the absorbent, which is beneficial to removing and purifying iodine elements in the iodine-rich gas and improving the iodine capture efficiency.
In one embodiment of the present disclosure, the mass concentration of iodine element in the iodine-rich gas in S2 is 1-500 mg/m3Preferably 50 to 200mg/m3(ii) a 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, the inorganic iodine may be 90% by mass or more and the organic iodine may be 0.01 to 1% by mass, 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-rich gas in S2 further comprises nitrogen oxides and/or radionuclides; the nitrogen oxides include nitric oxide and nitrogen dioxide (NO)2) Dinitrogen trioxide (N)2O3) Dinitrogen tetroxide (N)2O4) And dinitrogen pentoxide (N)2O5) One or more of the above; the radionuclide comprises3H、84Br、85Kr and133one or more Xe. In the above embodiment, the iodine-rich gas contains a large amount of toxic and harmful impurity elements, and the method disclosed by the invention can capture not only gaseous iodine in the iodine-rich gas, but also nitrogen oxide, so that the content of the impurity elements is reduced, and the pollution to the environment is reduced; the sodium hydroxide can react with the nitrogen oxide to generate sodium nitrate and sodium nitrite, and the hydrazine hydrate can react with the nitrogen oxide to generate nitrogen, so that the content of the nitrogen oxide is obviously reduced, and the pollution to the atmosphere is reduced.
In one embodiment of the present disclosure, the iodine-rich gas generated in the S2 is generated by a spent fuel post-treatment process, and the temperature of the iodine-rich gas is 80 to 100 ℃, preferably 90 to 100 ℃; the flow ratio of the absorbent solution to the iodine-rich gas is (5-80): 1, preferably (5-20): 1. in the above embodiment, the temperature of the iodine-rich tail gas is greater than 77 ℃ and not greater than 100 ℃, for example, may be 80 to 100 ℃, so as to prevent the iodine in the iodine-rich tail gas from being desublimated and precipitated in the transportation process.
In an embodiment of the present disclosure, the method further includes performing a purification process on the mixed gas obtained in S2, where the purification process includes: demisting the mixed gas, discharging the demisted mixed gas from a gas outlet at the top of the spray tower, and introducing the demisted mixed gas into a sodium hydroxide aqueous solution through a gas inlet of an alkali liquor tank for purification; in a preferred embodiment, the purified tail gas is detected, the tail gas which is qualified in detection is discharged into the atmosphere, and the tail gas which is unqualified in 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 the sodium iodate remaining in the mixed gas, so as to obtain the tail gas with low impurity content and low pollution, which is beneficial to being discharged into the atmosphere.
In one embodiment of the present disclosure, the defogging is performed by using a defogger, the defogger is a wire mesh defogger, and the defogging efficiency of the wire mesh defogger is more than 99%. In the above embodiment, the iodine-rich solution carried in the mixed gas can be removed by using a preferable demister, and the pure mixed gas is introduced into the alkaline solution tank to be purified, thereby avoiding contamination of the sodium hydroxide aqueous solution and reducing the amount of waste liquid to be treated.
In one embodiment of the present disclosure, the concentration of the sodium hydroxide aqueous solution in the lye tank is 0.5 to 3mol/L, the gas inlet of the lye tank is located below the liquid level of the sodium hydroxide aqueous solution, and the height of the gas inlet from the liquid level is 0.8 to 1.2 m. In the above embodiment, the mixed gas is introduced into the aqueous sodium hydroxide solution having a preferred concentration and height, so that the iodine element remaining in the mixed gas can be sufficiently absorbed, and the environmental pollution caused by the iodine element can be reduced.
According to the method provided by the disclosure, the absorbent solution is atomized to obtain absorbent liquid drops with a proper diameter, so that the absorbent liquid drops are fully contacted with the iodine-rich gas to generate chemical reaction and gas-liquid mass transfer, the gaseous iodine is effectively removed and purified, the nitrogen oxide can be captured, and the content of impurity elements is reduced; the method disclosed by the invention can effectively trap gaseous iodine without introducing strong oxidizing gas and only by adopting absorbent solution with smaller concentration, improves the capture efficiency of organic iodine, reduces the emission of radioactive iodine and the usage amount of the absorbent, and reduces the waste liquid treatment cost and the factory operation cost; simple operation, high trapping efficiency and small damage degree to equipment, and is suitable for industrial large-scale application.
The present disclosure is further illustrated by the following examples, but the present disclosure is not limited thereto, and the experimental methods used in the following examples and comparative examples are conventional ones, unless otherwise specified.
The spiral atomizing nozzle was purchased from shanghai fizepin atomizing systems, ltd;
the average diameter of the droplets was measured as follows: the method comprises the following steps of (1) shooting an original picture in a test by using a particle size measuring system, selecting an area with a good effect and clear liquid drops for processing, marking the area with software, obtaining the particle size of each liquid drop by using a software built-in algorithm, and performing statistical analysis; wherein the particle size measuring 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: performing ion chromatography according to a method specified by national standard GBZ T160.85-2007, wherein the instrument model is ICS 5000;
the method for testing the concentration of gaseous methyl iodide in tail gas comprises the following steps: the test is carried out by a spectrophotometer and a 1, 2-naphthoquinone-4-sodium sulfonate spectrophotometry, and the instrument model is a Leibetake ultraviolet visible spectrophotometer UV 1900.
Example 1
S1, inputting an absorbent solution with the temperature of 60 ℃ and the flow rate of 100mL from the top of a spray tower by using a peristaltic pump, and forming absorbent atomized liquid drops with the average diameter of 80 mu m through a spiral atomization nozzle arranged in the spray tower; wherein the absorbent solution is composed of 0.1mol/L sodium hydroxide solution and 0.05mol/L N2H4·H2O, the temperature of the spray tower is 60 ℃, the height is 0.7m, and the diameter is 0.08 m; the spray tower is provided with two spray layers, the upper spray layer is 0.55m in height and is provided with 3 spiral atomizing nozzles, and the lower spray layer is 0.45m in height and is provided with 2 spiral atomizing nozzles; the aperture of the spiral atomizing nozzle is 0.635mm, and the pressure is 6 multiplied by 104Pa, spraying angle is 105 degrees;
s2, subjecting the iodine-rich gas with the temperature of 90 ℃ generated in the post-treatment process of the spent fuel (the mass concentration of iodine element in the iodine-rich gas is 100 mg/m)3The mass of the iodine element in the methyl iodide is 0.5 percent based on the total mass of the iodine element in the iodine-rich gas; wherein the iodine-rich gas further comprises nitric oxide and nitrogen dioxide (NO)2) Dinitrogen trioxide (N)2O3)、3H、84Br、85Kr and133xe) is introduced from the bottom of the spray tower and is in countercurrent contact with the atomized absorbent liquid drops sprayed by the spiral atomizing nozzle from bottom to top, chemical reaction and gas-liquid mass transfer are generated on the surfaces of the liquid drops, mixed gas and iodine-rich solution are obtained, and the iodine-rich solution is discharged from the bottom of the tower and enters a waste liquid storage tank; wherein the flow rate of the iodine-rich gas is 20 mL/min;
s3, removing entrained liquid drops from the mixed gas through a wire mesh demister, discharging the mixed gas from a gas outlet at the top of the spray tower (the demisting efficiency of the wire mesh demister is 99.5%), introducing the mixed gas into a sodium hydroxide aqueous solution through a gas inlet of an alkali liquor tank for purification to obtain tail gas 1, introducing the tail gas 1 into a detection device, discharging the tail gas into the atmosphere after the tail gas is qualified through detection, and returning the tail gas which is unqualified through detection to the spray tower for continuous treatment (the concentration of the sodium hydroxide aqueous solution is 2mol/L, the gas inlet of the alkali liquor tank is positioned below the liquid level of the sodium hydroxide aqueous solution, and the height of the gas inlet from the liquid level of the sodium hydroxide aqueous solution is 1 m).
Example 2
The method of example 1 is used, with the only difference that: the absorbent solution in S1 is 0.1mol/L sodium hydroxide solution, and tail gas 2 is obtained.
Example 3
The method of example 1 is used, with the only difference that: the absorbent solution in S1 is 0.05mol/L of N2H4·H2And O, obtaining tail gas 3.
Example 4
The method of example 1 is 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 method of example 1 is used, with the only difference that: and the concentration of the sodium hydroxide solution in the S1 absorbent solution is 2mol/L, and the tail gas 5 is obtained.
Example 6
The method of example 1 is used, with the only difference that: s1 the spiral atomizing nozzle has an aperture of 2mm and a pressure of 3X 104Pa, the average diameter of atomized liquid drops of the atomized absorbent is about 500 mu m, and the tail gas 6 is obtained.
Example 7
The method of example 1 is used, with the only difference that: s1, replacing the spiral atomizing nozzle with a standard fan-shaped nozzle with the aperture of 0.5mm and the pressure of 6 x 104Pa, the average diameter of atomized liquid drops of the atomized absorbent is 2000 mu m, and the tail gas 7 is obtained.
Comparative example 1
The method of example 1 is used, with the only difference that: and (3) inputting an absorbent solution from the top of the spray tower without adopting a spiral atomizing nozzle, and then directly leaching the iodine-rich gas, wherein the average diameter of leaching liquid drops is 5000 micrometers, so as to obtain the comparative tail gas 1.
Test example
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 methyl iodide 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 methyl iodide;
the capture efficiency of the gaseous iodine element is (mass concentration of iodine element in iodine-rich gas-mass concentration of iodine element in tail gas)/mass concentration of iodine element in iodine-rich gas;
the gaseous methyl iodide capturing efficiency (mass concentration of iodine element in methyl iodide in the iodine-rich gas — mass concentration of iodine element in methyl iodide in the off gas)/mass concentration of iodine element in methyl iodide in the iodine-rich gas.
TABLE 1
Comparing the data of the comparative example 1 with the data of the example 1, it can be seen that, in the comparative example 1, the technical scheme of the atomization treatment disclosed by the present disclosure is not adopted, but the leaching liquid drops with the average diameter of 5000 μm are used for leaching, the content of iodine element in the obtained tail gas is high, the iodine capture efficiency is poor, the capture efficiency of the gaseous iodine simple substance is less than 75%, and the capture efficiency of the gaseous methyl iodide is less than 18%.
Comparing the data of example 1 with those of examples 2 to 5, it can be seen that the concentration of sodium hydroxide in the absorbent solution preferably used in the present disclosure in example 1 is 0.05 to 0.5mol/L, and N is2H4·H2The concentration of O is 0.05-0.5 mol/L, and the absorbent solution contains sodium hydroxide and N2H4·H2O, sodium hydroxide and N2H4·H2The concentration ratio of O is (1-10): 1, the iodine capture efficiency is higher, the capture efficiency of the iodine simple substance is more than 99%, and the capture efficiency of the methyl iodide is more than 39%; the concentration of the sodium hydroxide adopted in the embodiment 1 is low, the sodium hydroxide remained in the spray head is not easy to crystallize after the trapping process is finished, the spray head and a pipeline are prevented from being blocked, the factory maintenance cost is reduced, the equipment loss is reduced, and the method is suitable for industrial large-scale application; comparing the data of example 1 and example 6, it can be seen that the preferred spiral atomizing nozzle of the present disclosure in example 1 has a pore diameter of 0.5 to 0.7mm and a pressure of 5 × 104～10×104In the technical scheme of Pa, the capturing efficiency of iodine simple substances and iodomethane is high; comparing the data of example 1 with that of example 7, it can be seen that in example 1, when the preferred spiral atomizing nozzle of the present disclosure is adopted to perform the atomizing treatment, the obtained atomized droplets have small average diameter, uniform distribution (the droplet diameter is basically in the range of the average diameter), and iodine capturing effectThe rate is higher, and the iodine element content in the tail gas is lower. The method disclosed by the invention is simple to operate and high in trapping efficiency, can effectively trap gaseous iodine by adopting a spray absorption method, reduces radioactive iodine emission and environmental pollution, and is suitable for industrial large-scale application.
The preferred embodiments of the present disclosure have been described in detail above, however, the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present disclosure within the technical idea of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.
It should be noted that, in the foregoing embodiments, various features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, various combinations that are possible in the present disclosure are not described again.
In addition, any combination of various embodiments of the present disclosure may be made, and the same should be considered as the disclosure of the present disclosure, as long as it does not depart from the spirit of the present disclosure.
Claims (10)
1. A method of capturing gaseous iodine, the method comprising:
s1, introducing the absorbent solution into a spray tower for atomization treatment to obtain absorbent atomized liquid drops;
s2, introducing iodine-rich gas into the spray tower, and enabling the iodine-rich gas to be in countercurrent contact with the atomized liquid drops of the absorbent from bottom to top to obtain mixed gas and an iodine-rich solution;
wherein the absorbent solution comprises sodium hydroxide and/or N2H4·H2O, the iodine-rich 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 0.05-0.5 mol/L, and the N is2H4·H2The concentration of O is 0.05-0.5 mol/L; preferably, the absorbent solutionContaining sodium hydroxide and N2H4·H2O, the sodium hydroxide and the N2H4·H2The concentration ratio of O is (1-10): 1; the temperature of the absorbent solution is 60 ℃ to 80 ℃, and preferably 70 ℃ to 80 ℃.
3. The method according to claim 1, wherein the atomization process in S1 is performed 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 104～10×104Pa, the spraying angle is 100-115 degrees; wherein the average diameter of the atomized droplets of the absorbent is 60-150 μm; preferably, the atomizing nozzle is a hydraulic spiral atomizing nozzle.
4. The method according to claim 1, wherein 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 (8-12): 1;
the spray tower comprises two spray layers, and the height difference of the two spray layers is 5-20 mm, preferably 10-20 mm.
5. The method of claim 1, wherein the mass concentration of iodine element in the iodine-rich gas in S2 is 1-500 mg/m3Preferably 50 to 200mg/m3(ii) a The mass of the iodine element in the methyl iodide is less than 1% based on the total mass of the iodine element in the iodine-rich gas.
6. The method of claim 1, wherein the iodine-rich gas in S2 further comprises nitrogen oxides and/or radionuclides; the nitrogen oxides include nitric oxide and nitrogen dioxide (NO)2) Dinitrogen trioxide (N)2O3) Dinitrogen tetroxide (N)2O4) And dinitrogen pentoxide (N)2O5) One or more of the above; the radionuclide comprises3H、84Br、85Kr and133one or more Xe.
7. The method according to claim 1, wherein the iodine-rich gas generated in the post-treatment process of the spent fuel in S2 is at a temperature of 80-100 ℃, preferably 90-100 ℃; the flow ratio of the absorbent solution to the iodine-rich gas is (5-80): 1, preferably (5-20): 1.
8. the method according to claim 1, further comprising subjecting the mixed gas obtained in S2 to a purification treatment, wherein the purification treatment comprises: demisting the mixed gas, discharging the demisted mixed gas from a gas outlet at the top of the spray tower, and introducing the demisted mixed gas into a sodium hydroxide aqueous solution through a gas inlet of an alkali liquor tank for purification.
9. The method of claim 8, wherein the demisting is performed using a demister, the demister being a wire mesh demister, the wire mesh demister having a demisting efficiency of 99% or more.
10. The method according to claim 8, wherein the concentration of the sodium hydroxide aqueous solution in the lye tank is 0.5 to 3mol/L, the gas inlet of the lye tank is positioned below the liquid surface of the sodium hydroxide aqueous solution, and the height of the gas inlet from the liquid surface is 0.8 to 1.2 m.
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