JP2018134571A - Removal method of iodine compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a removal method of an iodine compound, not depositing solid iodine, when removing gaseous hydrogen iodide or iodine fluoride from gas by a wet removal method.SOLUTION: In a removal method of an iodine compound, gas containing the gaseous iodine compound expressed in formula (1) is brought into contact with a basic aqueous solution containing sodium hydroxide, potassium hydroxide, rubidium hydroxide or cesium hydroxide as a basic substance, and further containing thiosulfate or sulfite salt as a reductive substance, to thereby remove the iodine compound.SELECTED DRAWING: None

Description

  The present invention relates to a method for removing an iodine compound from a gas containing a gaseous iodine compound. The gaseous iodine compound is used as an etching gas or a cleaning gas in the electronics industry or the nuclear power industry such as a fluorinating agent and a semiconductor manufacturing process, and it is necessary to remove the iodine compound when used and exhausted to the atmosphere.

Gaseous iodine compounds include hydrogen iodide (HI), iodine monofluoride (IF) as iodine fluoride, iodine trifluoride (IF ₃ ), iodine pentafluoride (IF ₅ ) and iodine heptafluoride ( IF ₇ ). In particular, hydrogen iodide, iodine pentafluoride or iodine heptafluoride is useful as an etching gas or cleaning gas in the electronic industry or the nuclear power industry such as fluorinating agents and semiconductor manufacturing processes, and iodine heptafluoride is particularly useful. is there.
However, hydrogen iodide and iodine fluoride are irritating, and it is necessary to remove hydrogen iodide and iodine fluoride when discharging a gas containing used hydrogen iodide or iodine fluoride into the atmosphere. .

  Examples of methods for removing hydrogen iodide and iodine fluoride from a gas containing hydrogen iodide or iodine fluoride include a dry removal method and a wet removal method.

  The dry removal method is a method of removing a gas to be removed by circulating a gas containing the gas to be removed through a solid removing agent. When removing the gas to be removed from the gas containing the gas to be removed, when the dry removal method is used, it is possible to reduce the apparatus for removing the gas to be removed, and the removal operation is simple. Have. However, if the amount of gas processed per unit time is increased when removing the gas to be removed from the gas containing the gas to be removed, there is a risk of sudden heat generation. Since it is necessary, there are problems such as frequent replacement of the solid removal agent as the gas throughput increases.

  For example, Patent Document 1 discloses an alkali metal oxide, an alkali metal carbonate, an alkaline earth metal carbonate, an alkaline earth metal, an alkaline earth metal oxide, an alkali metal hydroxide, or an alkaline earth metal hydroxide. A reactant (solid removal agent) containing 5% by mass or more and 100% by mass or less of a total of the substances at a temperature of 0 ° C. or more and 540 ° C. or less, represented by a general formula: IFx (where x is 1, 3 or 5 or 7)), and the iodine component and the fluorine component are fixed to the reactant by contact with a gas containing 10 vol% or less. A method for removing iodine fluoride by a dry removal method is disclosed.

  On the other hand, the wet removal method is a method in which a liquid removal agent is used and the liquid removal agent absorbs the gas to be removed and is removed.

If the wet removal method is used to remove the gas to be removed from the gas containing the gas to be removed, the following advantages (A) to (D) are obtained over the dry removal method.
(A) Compared with the dry removal method using a solid removal agent, when removing the gas to be removed from the gas containing the gas to be removed, there is less heat generation with respect to the gas throughput per unit time.
(B) The heat generated by the liquid removal agent due to absorption of the gas to be removed can be removed by using the heat of vaporization of water, or can be removed by a heat exchanger.
(C) The liquid removing agent can be easily replaced with a pump or the like.
(D) Compared with the dry removal agent, the replacement of the liquid removal agent is simple.

  However, as compared with the dry removal method, the removal of the gas to be removed in the wet removal method using the liquid removing agent requires a removal device and a long processing time which are large in amount with respect to the processing amount.

  For example, Patent Document 2 and Patent Document 3 disclose a method of adding a reducing substance to a liquid remover with respect to a wet removal method of fluorine gas or chlorine trifluoride. Specifically, Patent Document 2 discloses a fluorine gas removal characterized by using a mixed liquid of alkali sulfite and caustic alkali as an absorbing liquid when absorbing and removing a fluorine component from exhaust gas containing fluorine gas. A method is disclosed. Further, it is described that by using this wet removal report, the fluorine in the exhaust gas can be reduced to 1 ppm by volume or less with a relatively small device. Patent Document 3 discloses a wet treatment method for exhaust gas containing chlorine trifluoride, wherein the exhaust gas containing chlorine trifluoride is washed with a mixed aqueous solution of alkali and sulfite or bisulfite. ing.

Further, Patent Document 4 discloses that water or water vapor is added to an exhaust gas containing a fluorine-based gas composed of F ₂ gas, halogen fluoride, oxygen fluoride, and a mixed gas thereof, and the fluorine-based gas in the exhaust gas in a volume ratio. Supplying more than 50 times the amount of gas, reacting the exhaust gas with water or water vapor at 300 to 400 ° C., and decomposing it into hydrogen halide and oxygen that are easily absorbed by water A method is disclosed.

  Further, in Patent Document 5, an alkali metal compound and a solvent are mixed with waste containing iodine or an iodine compound, and the mixture is introduced into a combustion furnace having a combustion device and heat-treated, and is contained in the heat treatment gas. A method for recovering iodine is disclosed, wherein the iodine compound is absorbed in an alkaline aqueous solution. Specifically, the step of adding sodium hydroxide and water to the waste containing iodine or iodine compound, the step of spraying into a high-temperature combustion furnace using natural gas as fuel, the gas discharged from the combustion furnace as water A method for recovering iodine is described in which a step of contacting with an aqueous sodium oxide solution and then a step of adding purified chlorine to the aqueous sodium hydroxide solution after contact to obtain purified iodine are described.

JP 2011-005477 A JP-A-2-233122 JP-A-3-217217 JP 2006-289238 A JP-A-6-157005

However, when the wet removal method described in Patent Document 2 and Patent Document 3 is applied to removing hydrogen iodide or iodine fluoride from a gas containing hydrogen iodide or iodine fluoride as a gas to be removed, Hydrogen iodide or iodine fluoride dissolves in an aqueous solution as iodine ion (I ⁻ ), iodate ion (IO ₃ ⁻ ) or triiodine ion (I ₃ ⁻ ), but there is a problem that solid iodine is precipitated. It was.

  When the exhaust gas treatment method described in Patent Literature 4 is applied to wet removal of iodine fluoride from a gas containing iodine fluoride, iodine fluoride is reacted with high-temperature steam to generate hydrogen fluoride and hydrogen iodide. And a device for absorbing the produced hydrogen fluoride and hydrogen iodide are required, and the process is complicated.

  The process for recovering iodine described in Patent Document 5 is complicated. Moreover, in the Example, in the process which contacts the gas discharged | emitted from the inside of a combustion furnace with sodium hydroxide aqueous solution, 0.6g-1.0g iodine is discharge | released in air | atmosphere, iodine loss rate 0.02 mass%- It is described that it is 0.05 mass%.

  The present invention solves such a problem, and deposits solid iodine when removing hydrogen iodide or iodine fluoride in a gas containing iodine or hydrogen fluoride as an iodine compound gas by a wet removal method. An object of the present invention is to provide a simple method for removing an iodine compound that can be removed so that the concentration becomes extremely low without any problems.

  The inventors removed hydrogen iodide, iodine pentafluoride, and iodine heptafluoride from a gas containing hydrogen iodide, iodine pentafluoride, or iodine heptafluoride as a gas to be removed. When hydrogen iodide, iodine pentafluoride, and iodine heptafluoride were absorbed, solid iodine precipitated and adhered to the inner wall of the pipe and the device. Such adhesion of iodine may lead to clogging of piping and the like, and is not an efficient method for removing hydrogen iodide, iodine pentafluoride or iodine heptafluoride.

  Therefore, as a result of diligent investigations, the present inventors have unexpectedly found that a gas containing hydrogen iodide, iodine pentafluoride or iodine heptafluoride is brought into contact with an aqueous solution of a basic substance using a packed tower. The present inventors have found that it can be wet-removed to a very low concentration without precipitation of solid iodine, and have reached the present invention.

  That is, the present invention provides a method for removing an iodine compound by a wet removal method in which a gas containing hydrogen iodide or iodine fluoride as an iodine compound is brought into contact with an aqueous solution of a basic substance to wetly remove iodine fluoride. To do.

The present invention includes the following inventions 1 to 11.
[Invention 1]
A method for removing an iodine compound, wherein a gas containing an iodine compound represented by formula (1) is brought into contact with a basic aqueous solution by using a gas-liquid contact device to remove the iodine compound.

[Invention 2]
The method for removing an iodine compound according to invention 1, wherein the gas-liquid contact device is a packed tower packed with a filler.
[Invention 3]
The method for removing an iodine compound according to Invention 2, wherein the contact is carried out by countercurrent contact.
[Invention 4]
The iodine compound removal method according to any one of Inventions 1 to 3, wherein the iodine compound is hydrogen fluoride (HI), iodine pentafluoride (IF ₅ ), or iodine heptafluoride (IF ₇ ).
[Invention 5]
The basic substance contained in the basic aqueous solution is an alkali metal hydroxide, and is at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide. A method for removing iodine compounds.
[Invention 6]
The basic substance contained in the basic aqueous solution is an alkaline earth metal hydroxide, and is at least one selected from the group consisting of magnesium hydroxide, calcium hydroxide, strontium hydroxide or barium hydroxide. 4. Method for removing iodine compound
[Invention 7]
The iodine compound removing method according to any one of Inventions 1 to 6, wherein the concentration of the basic substance in the basic aqueous solution is 0.0001% or more and 10% or less in terms of mass%.
[Invention 8]
The method for removing an iodine compound according to any one of Inventions 1 to 7, wherein the basic aqueous solution is a basic aqueous solution further containing a reducing substance.
[Invention 9]
The method for removing an iodine compound according to Invention 8, wherein the reducing substance is thiosulfate or sulfite.
[Invention 10]
The removal method of the iodine compound of the invention 8 or the invention 9 whose content of the reducing substance in the aqueous solution is 0.0001 mass% or more and 10 mass% or less.
[Invention 11]
The removal method of the iodine compound of the invention 1-10 whose temperature of the said aqueous solution is 10 degreeC or more and 60 degrees C or less.
[Invention 12]
The iodine compound is iodine pentafluoride (IF ₅ ) or iodine heptafluoride (IF ₇ );
The method for removing an iodine compound according to Invention 1, wherein the basic aqueous solution is a basic aqueous solution containing a reducing substance.

  If the iodine compound removal method of the present invention is used, when hydrogen iodide or iodine fluoride in a gas containing hydrogen iodide or iodine fluoride is dissolved by a wet removal method, without precipitation as solid iodine, It can be easily removed by a wet removal method. In particular, when a reducing substance is added to a basic aqueous solution, hydrogen iodide or iodine fluoride can be removed at a very low concentration from a gas containing hydrogen iodide or iodine fluoride.

It is the schematic of the removal apparatus for enforcing the removal method of the iodine compound of this invention.

  This invention is the removal method of an iodine compound which makes the gas containing the iodine compound represented by Formula (1) contact a basic aqueous solution, and removes an iodine compound.

[Contact of water containing hydrogen iodide, iodine pentafluoride or iodine heptafluoride with water]
When a gas containing hydrogen iodide, iodine pentafluoride or iodine heptafluoride as a gas to be removed is brought into contact with water, solid iodine precipitates and adheres to the inner wall of the pipe or device.
It was estimated that iodate ions, specifically IO ₃ ⁻ , IO ₄ ⁻ and IO ₆ ⁵⁻ , which are strong oxidants in water, are generated, and solid iodine is precipitated, for example, according to the following chemical equilibrium formula.

Moreover, it was estimated that the dissolved oxygen or light in water oxidizes triiodine ion (I ₃ ⁻ ) or iodine ion (I ⁻ ), and solid iodine is precipitated by the reaction represented by the following formula.

[Contact between gas containing hydrogen iodide, iodine pentafluoride or iodine heptafluoride and basic aqueous solution]
In the method for removing an iodine compound of the present invention, the precipitation of solid iodine was unexpectedly stopped by using a basic aqueous solution instead of water. This is presumed that precipitation of solid iodine does not occur because the iodate ion (IO ₃ ⁻ ) takes a chemical equilibrium state not via solid iodine as shown in the following formula.

In the method for removing an iodine compound of the present invention, it is presumed that the effect of iodate ion (IO ₃ ⁻ ) as an oxidizing agent becomes weak as a result of using a basic aqueous solution instead of water.

[Addition of reducing substances]
In the method for removing an iodine compound of the present invention, by adding a reducing substance to the basic aqueous solution, the effect of removing the iodine compound by bringing a gas containing the iodine compound into contact with the basic aqueous solution can be enhanced. Specifically, as shown in the examples of the present specification, by adding sodium thiosulfate or sodium sulfite to a basic aqueous solution, the concentration of the exit iodine compound was 500 ppm by volume when not added. And reduced to 0.5 ppm by volume or less.

In addition, when a reducing substance is added to the basic aqueous solution, the iodate ion (IO ₃ ⁻ ) can be reduced to triiodine ion (I ₃ ⁻ ) or iodine ion (I ⁻ ). Is preferred. If no reducing substance is added, it is presumed that iodine is dissolved mainly as iodate ions (IO ₃ ⁻ ) having high oxidizing power. Compared to iodate ion (IO ₃ ⁻ ), iodine ion (I ⁻ ) and triiodine ion (I ₃ ⁻ ) have low oxidizing power. By adding a reducing substance, it is presumed that iodate ion (IO ₃ ⁻ ) can be reduced to iodine ion (I ⁻ ) or triiodate ion (I ₃ ⁻ ). Moreover, it is estimated that the addition of a reducing substance improves the removal efficiency of iodine fluoride and the removal efficiency of oxidizing gas such as iodine pentafluoride oxide (IOF ₅ ) generated by the reaction between iodine fluoride and water. Is done.

  Hereinafter, the present invention will be described in detail. However, the description of the constituent elements described below is an example of the embodiment of the present invention, and is not limited to these specific contents. Various modifications can be made within the scope of the gist.

[Gaseous iodine compounds]
In the method for removing iodine compound gas of the present invention, a gas containing hydrogen iodide or iodine fluoride as a gaseous iodine compound is brought into contact with a basic aqueous solution to remove the iodine compound. As iodine fluoride, at least one selected from the group consisting of iodine monofluoride (IF), iodine trifluoride (IF ₃ ), iodine pentafluoride (IF ₅ ), and iodine heptafluoride (IF ₇ ) is used. Can be used. Gases to be removed in the iodine compound gas removal method of the present invention are preferably hydrogen fluoride (HI), iodine pentafluoride (IF ₅ ) and iodine heptafluoride (IF ₇ ), particularly preferably. Is iodine heptafluoride (IF ₇ ).

  The gas containing hydrogen iodide or iodine fluoride may contain two or more kinds of iodine fluoride of these gaseous iodine compounds.

[Basic substances]
Examples of the basic substance used in the iodine compound removing method of the present invention include alkali metal hydroxides and alkaline earth metal hydroxides. Specific examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide. Specific examples of the alkaline earth metal hydroxide include magnesium hydroxide, calcium hydroxide, strontium hydroxide, and barium hydroxide. The basic substance used in the iodine compound removal method of the present invention may include any one or more of these basic substances. Alkali metal hydroxides are preferred because of their high solubility in water, preferably sodium hydroxide, potassium hydroxide, rubidium hydroxide or cesium hydroxide.

  The concentration of the basic substance in the basic aqueous solution used in the iodine compound removal method of the present invention varies depending on the type of the basic substance. In order to exhibit the effect of the basic substance, it is preferably 0.0001% by mass or more, expressed in mass% based on the entire basic aqueous solution. It is preferable to appropriately adjust the concentration of the basic aqueous solution so that precipitation of the basic substance and precipitation of the salt generated by the reaction between the basic substance and the gas to be removed do not occur. If it exceeds 10% by mass, precipitation is likely to occur, and preferably 10% by mass or less so that precipitation does not occur.

  In the iodine compound removal method of the present invention, it is preferable that the basic aqueous solution as the removal agent further contains a reducing substance dissolved in order to quickly remove the gaseous iodine compound as the removal target gas. As described above, the basic aqueous solution further contains a reducing substance dissolved therein, so that the reaction between hydrogen iodide or iodine fluoride and the reducing substance proceeds and quickly absorbs hydrogen iodide or iodine fluoride. Presumed to be.

[Reducing substances]
As a kind of reducing substance used for the removal method of the iodine compound of this invention, the substance with a reducing power stronger than a basic substance in basic aqueous solution can be mentioned. Such substances can include sulfur dioxide, carbon monoxide, ammonia, formate, hypophosphite, phosphorous acid, formaldehyde, sulfite or thiosulfate. These reducing substances may be used alone or in combination of a plurality of kinds. Preferred is thiosulfate or sulfite because of its high chemical stability, low toxicity and no toxic reaction products, high solubility of the reducing substance and low cost.

  Examples of the cation constituting thiosulfate or sulfite include alkali metal ions, alkaline earth metal ions, and onium ions. Specific examples of the alkali metal ions include lithium ions, sodium ions, potassium ions, rubidium ions, and cesium ions. Specific examples of the alkaline earth metal ion include magnesium ion, calcium ion, strontium ion, and barium ion. Specific examples of the onium ion include ammonium ions. The cation constituting the thiosulfate or sulfite that is a reducing substance used in the method for removing an iodine compound of the present invention is preferably an alkali metal ion or an onium ion because of its high solubility in water.

  The concentration of the reducing substance in the basic aqueous solution used in the method for removing the iodine compound of the present invention varies depending on the type of the reducing substance, but in order to exert the effect of the reducing substance, the mass based on the entire aqueous solution. In terms of%, it is preferably 0.0001% by mass or more. It is preferable to appropriately adjust the concentration of the reducing aqueous solution so that precipitation of the reducing substance and precipitation of the salt generated by the reaction between the reducing substance and the gas to be removed do not occur. If it exceeds 10% by mass, precipitation is likely to occur, and the amount is preferably 10% by mass or less so that precipitation does not occur.

  In the method for removing an iodine compound of the present invention, the temperature of the basic aqueous solution, which is a removing agent, when contacting a gas containing a gaseous iodine compound is 10 ° C. or higher within the temperature range where the removing agent exists as a liquid, 60 C. or lower is preferable. When the temperature is higher than 60 ° C., the water vapor pressure of the basic aqueous solution increases, and the amount of water vaporized from the remover increases, making it difficult to manage the concentration. More preferably, it is 10 degreeC or more and 40 degrees C or less.

[Gas-liquid contact between gas containing gaseous iodine compound and basic aqueous solution]
In the iodine compound removing method of the present invention, it is preferable to remove heat when a gas containing a gaseous iodine compound is continuously brought into gas-liquid contact with a basic aqueous solution as a removing agent. The calorific value varies depending on the combination of the removing agent and the iodine compound contained in the gas. It is preferable to remove heat by heat release from the apparatus or heat of vaporization of water to prevent the temperature of the aqueous solution of the basic substance from rising.

Further, as a method for preventing the temperature rise, there is a method of continuously contacting with a basic aqueous solution after diluting with another kind of gas so that the concentration of gaseous iodine compound is less than 10% by volume. it can. More preferably, after diluting with another kind of gas so that the concentration of the gaseous iodine compound is less than 2% by volume, the method is continuously contacted with the basic aqueous solution. Any kind of gas may be used as long as it does not react directly with the gaseous iodine compound or the reducing substance. Specific examples include nitrogen (N ₂ ), argon (Ar), helium (He), and perfluorocarbon. One kind of these gases may be used, or a plurality of kinds of gases may be used in combination.

[Gas-liquid contact device]
As a gas-liquid contact apparatus that can be used in the method for removing an iodine compound of the present invention, a stirring tank, a bubble tower, a plate tower, a spray tower, or a packed tower can be used. Among these gas-liquid contact devices, it is preferable to contact the gaseous iodine compound and the basic aqueous solution using a packed tower having good gas-liquid contact efficiency. In the present invention, the packed tower is an apparatus in which a packing for increasing the contact area of gas and liquid is arranged in the tower, and is an apparatus for performing gas-liquid contact on the surface of the packing. . The packed tower has a counter-current contact type in which a gaseous iodine compound and a basic aqueous solution are made to flow in contact in opposite directions, or a co-current contact type in which the gaseous iodine compound is made to flow and contact in the same direction, but preferably the gas-liquid contact efficiency is improved. Current contact.

  In the method for removing iodine compound of the present invention, the material of the portion in contact with the gaseous iodine compound and the basic aqueous solution in the gas-liquid contact device is preferably not corroded by the iodine compound, and is a base material made of iron or stainless steel. A resin lining is preferred. As the lining resin, a fluororesin is preferable. Examples of such a fluororesin include tetrafluoroethylene, vinylidene fluoride, chlorotrifluoroethylene, and the like. The packing in the packed tower is not particularly limited in shape as long as the contact area when contacting the gaseous iodine compound and the basic aqueous solution can be widened. The material of the filler is preferably not corroded by iodine compounds, and it is preferable to use a resin filler. Specifically, the said fluororesin can be mentioned.

<Effect of packed tower>
By using a packed tower in the gas-liquid contact device, as shown in Examples 1 to 18 below, the concentration of the iodide gas at the outlet of the packed tower was reduced to 500 ppm by volume or less.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the following examples.

  An embodiment of the present invention will be specifically described with reference to FIG. FIG. 1 is a schematic view of a removing apparatus for carrying out the iodine compound removing method of the present invention.

  As shown in FIG. 1, the components of the removal apparatus are: A) packed tower 1 packed with a packing material, B) a basic aqueous solution 2 containing a basic substance as a removing agent and, if necessary, a reducing substance, C) A liquid tank 3 for storing an aqueous solution, and D) a liquid feed pump 4 for feeding the aqueous solution in the liquid tank to the upper part of the packed tower. The packed tower 1 has a length of 1.5 m, a tower diameter of 25 A (34 mm), and the inside is covered with polytetrafluoroethylene which is a fluororesin. As the filler, a Raschig ring made of polytetrafluoroethylene having a diameter of φ1 / 4 inch (6.35 mm) and a length of 6 mm was used, and the filling length was 1.2 m.

  A basic aqueous solution 2 containing a basic substance and a reducing substance as a removing agent is sent from the liquid kettle 3 to the upper portion of the packed tower 1, and then flows through the packed tower 3 and is fed by the liquid feed pump 4 to the flow meter 5. While circulating the flow rate, the liquid was returned to the liquid kettle 3 to circulate. The circulation flow rate was 0.3 liter / min. Hydrogen iodide, iodine pentafluoride, or iodine heptafluoride diluted with nitrogen until the concentration reaches 1% by volume has a gas linear velocity of 1 cm / sec in the packed column 1 by the mass flow controller 6. In this way, it is introduced from the lower inlet 7 of the packed tower 1, makes countercurrent contact with the basic aqueous solution 2 containing a basic substance and a reducing substance as a removing agent, and is discharged from the upper outlet 8 of the packed tower 1. The concentration of hydrogen iodide, iodine pentafluoride, or iodine heptafluoride in the gas discharged from the upper outlet 8 of the packed column 1 is analyzed by a gas detector or a Fourier transform infrared spectrometer, and from the upper portion of the packed column 1 The concentration of hydrogen iodide, iodine pentafluoride, or iodine heptafluoride in the released gas is measured, and solid iodine is precipitated in the basic aqueous solution 2 containing a basic substance as a removing agent and a reducing substance. The presence or absence was confirmed.

  Specifically, the concentration of hydrogen iodide was measured using a gas detector (manufactured by Riken Keiki Co., Ltd., product name, portable toxic gas monitor, SC-8000). The concentrations of iodine pentafluoride and iodine heptafluoride were measured using a gas detector (manufactured by Shin Cosmos Electric Co., Ltd., product name, industrial stationary gas detection alarm device, PS-7). When the concentration of hydrogen iodide, iodine pentafluoride, or iodine heptafluoride is higher than the full scale of the gas detector, a Fourier transform infrared spectrometer (product name, IR-Tracer100, manufactured by Shimadzu Corporation) ) And measured.

[Evaluation results]
Examples 1-6, comparative example 1 (removal of hydrogen iodide)
In Examples 1 to 6, an aqueous solution of potassium hydroxide or sodium hydroxide, which is a basic substance, is used as a removing agent. In Examples 1, 2, and 5, sodium thiosulfate or sodium sulfite is further used as a reducing substance. added. In Comparative Example 1, only water was used as a removing agent without using a basic substance. In Examples 1 to 6 and Comparative Example 1, the composition of the removing agent and the evaluation results when hydrogen iodide is removed are shown in Table 1 below.

  As shown in Examples 1 to 6 and Example 7 of Table 1, the HI concentration at the lower inlet 7 of the packed tower was 1% by volume in the measurement by the gas detector or the Fourier transform infrared spectrometer. At the outlet 8, the HI concentration was reduced to 0.05 ppm by volume or less (iodine loss rate of 0.0005% by mass or less). In Examples 1 to 6, solid iodine was not precipitated in the basic aqueous solution 2, but solid iodine was precipitated in Comparative Example 1 using only water as the removing agent.

Examples 7-12, comparative example 2 (removal of iodine pentafluoride)
In Examples 7 to 12, a basic aqueous solution of potassium hydroxide or sodium hydroxide was used as a removing agent. In Examples 7, 8, and 11, sodium thiosulfate or sodium sulfite was further added as a reducing substance. It was. In Comparative Example 2, only water was used without using a basic substance as a removing agent. In Examples 7 to 12 and Comparative Example 2, the composition and evaluation results of the removal agent when iodine pentafluoride was removed are shown in Table 2 below.

As shown in Table 2, in the measurement with a gas detector or a Fourier transform infrared spectrometer, the IF ₅ concentration at the inlet 7 of the packed column was 1% by volume, whereas the aqueous solution of potassium hydroxide or hydroxide was used as the removing agent. The IF ₅ concentration at the packed tower outlet 8 of Examples 9, 10, and 12 using an aqueous potassium solution was reduced to 500 ppm by volume. Further, in Examples 7, 8, and 11 in which sodium thiosulfate or sodium sulfite as a reducing substance was added, the IF ₅ concentration at the packed tower outlet 8 was 0.5 ppm by volume or less (iodine loss rate of 0.005 mass% or less). ). On the other hand, in Comparative Example 3 using only water as the removing agent, the IF ₅ concentration at the packed tower outlet 8 was 1000 ppm by volume.

  Moreover, although solid iodine did not precipitate in basic aqueous solution 2 about Examples 7-12, in Comparative Example 2, solid iodine precipitated.

Examples 13-18, comparative example 3 (removal of iodine heptafluoride)
In Examples 13 to 18, an aqueous solution of potassium hydroxide or sodium hydroxide, which is a basic substance, is used as a removing agent. In Examples 13, 14, and 17, sodium thiosulfate or sodium sulfite is further used as a reducing substance. added. In Comparative Example 3, only water was used without using a basic substance as a removing agent. In Examples 13 to 18 and Comparative Example 3, the composition of the removing agent when iodine heptafluoride was removed and the evaluation results are shown in Table 3 below.

As shown in Table 3, in the measurement with a gas detector or a Fourier transform infrared spectrometer, the IF ₅ concentration at the inlet 7 of the packed column was 1% by volume, whereas the aqueous solution of potassium hydroxide or hydroxide was used as the removal agent. The IF ₇ concentration at the packed tower outlet 8 of Examples 13, 15, and 18 using an aqueous potassium solution was reduced to 500 ppm by volume. Further, in Examples 13, 14, and 17 in which sodium thiosulfate or sodium sulfite as a reducing substance was added, the IF ₇ concentration at the packed tower outlet 8 was 0.5 ppm by volume or less (iodine loss rate of 0.005 mass% or less). ). On the other hand, in Comparative Example 3 using only water as the removing agent, the IF ₇ concentration at the packed tower outlet 8 was 1000 ppm by volume.

  Moreover, although solid iodine did not precipitate in basic aqueous solution 2 about Examples 13-18, in Comparative Example 2, solid iodine precipitated.

1: packed tower 2: basic aqueous solution 3: liquid kettle 4: liquid feed pump 5: flow meter 6: mass flow controller 7: inlet (of packed tower) 8: outlet (of packed tower)

Claims (12)

A method for removing an iodine compound, wherein a gas containing an iodine compound represented by formula (1) is brought into contact with a basic aqueous solution by using a gas-liquid contact device to remove the iodine compound.

The method for removing an iodine compound according to claim 1, wherein the gas-liquid contact device is a packed tower filled with a filler. The method for removing an iodine compound according to claim 2, wherein the contact is performed by countercurrent contact. The iodine compound according to any one of claims 1 to 3, wherein the iodine compound is hydrogen fluoride (HI), iodine pentafluoride (IF ₅ ), or iodine heptafluoride (IF ₇ ). Removal method. The basic substance contained in the basic aqueous solution is an alkali metal hydroxide, and is at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide. Item 5. The method for removing an iodine compound according to any one of Items4. The basic substance contained in the basic aqueous solution is an alkaline earth metal hydroxide, and is at least one selected from the group consisting of magnesium hydroxide, calcium hydroxide, strontium hydroxide or barium hydroxide. The removal method of the iodine compound of any one of thru | or 4 thru | or 4.   The method for removing an iodine compound according to any one of claims 1 to 6, wherein the concentration of the basic substance in the basic aqueous solution is 0.0001% or more and 10% or less in terms of mass%. The method for removing an iodine compound according to claim 1, wherein the basic aqueous solution is a basic aqueous solution further containing a reducing substance. The method for removing an iodine compound according to claim 8, wherein the reducing substance is thiosulfate or sulfite. The removal method of the iodine compound of Claim 8 or Claim 9 whose content of the reducing substance in the said aqueous solution is 0.0001 mass% or more and 10 mass% or less. 11. The method for removing an iodine compound according to claim 1, wherein the temperature of the aqueous solution is 10 ° C. or higher and 60 ° C. or lower. The iodine compound is iodine pentafluoride (IF ₅ ) or iodine heptafluoride (IF ₇ );
The basic aqueous solution is a basic aqueous solution containing a reducing substance.
The method for removing an iodine compound according to claim 1.

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