Sulfur dioxide mixture, method for producing the same, and filling container

Abstract

To provide a sulfur dioxide mixture which hardly corrodes metals.SOLUTION: The sulfur dioxide mixture contains sulfur dioxide and water. Then, the sulfur dioxide mixture is filled in the filling container so that a gas phase and a liquid phase exist, and a moisture concentration of the gas phase is 0.005 mol ppm or more and less than 5000 mol ppm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a sulfur dioxide mixture, a method for producing the same, and a container for filling the mixture. [Background technology]

[0002] Sulfur dioxide (SO2) has traditionally been used for a variety of purposes, including as a food additive, raw material for industrial chemicals, and raw material for pharmaceuticals, but in recent years its use has been increasing in semiconductor microfabrication applications, which require high-purity sulfur dioxide, and there is growing demand for improved quality. However, liquefied sulfur dioxide filled in a container has the following problem: Sulfur dioxide contains a trace amount of moisture that is difficult to remove during the manufacturing process. Even when high-purity sulfur dioxide with a sufficiently low moisture concentration is filled in a container, the moisture can concentrate inside the container, and sulfur dioxide gas with an insufficient moisture concentration may be released from the container. This problem is described in detail below.

[0003] When vaporized sulfur dioxide gas is released from a filled container, the liquid sulfur dioxide evaporates to maintain gas-liquid equilibrium within the container. Since moisture, which has a vapor-liquid equilibrium constant of approximately 0.5, evaporates less than sulfur dioxide and tends to remain in the liquid phase, the moisture is concentrated within the container as the sulfur dioxide gas is released. Therefore, at the beginning of release, the amount of moisture accompanying the sulfur dioxide gas is very small, and the moisture concentration of the sulfur dioxide gas is sufficiently low. However, as the liquid phase decreases due to evaporation, the amount of moisture accompanying the sulfur dioxide gas gradually increases, and the moisture concentration of the sulfur dioxide gas increases.

[0004] For example, sulfur dioxide, which is generally considered to be high purity, has a liquid phase moisture concentration of approximately 500 mol ppm when it is fully filled into a container, but as the sulfur dioxide gas is released from the container, the moisture concentrates in the liquid phase, and when all the liquefied sulfur dioxide has finally gasified, the moisture concentration in the gas phase rises to 50,000 mol ppm. Products with lower moisture concentrations are also available on the market, but even so, the liquid phase moisture concentration when it is fully filled into a container is approximately 60 mol ppm, and when all the liquefied sulfur dioxide has finally gasified, the moisture concentration in the gas phase is 6,000 mol ppm.

[0005] If sulfur dioxide gas has a high moisture concentration, moisture tends to adhere to the inner walls of the pipes through which it flows. The sulfur dioxide is absorbed by this moisture to form sulfurous acid, which is then further oxidized to sulfuric acid, potentially corroding and deteriorating the pipes and increasing repair costs. Furthermore, if the deterioration of the pipes progresses and sulfur dioxide gas, which is harmful to humans, leaks, this could lead to a disaster or accident. Furthermore, since the pipes are often made of stainless steel, heavy metals such as nickel, chromium, and iron that have dissolved from the pipes due to corrosion could become entrained in the sulfur dioxide gas. For example, when sulfur dioxide gas is used as an etching gas for semiconductor wafers, these heavy metals could adhere to the wafer surface and contaminate the wafers.

[0006] To solve this problem, for example, Patent Document 1 discloses a method for removing moisture from sulfur dioxide gas by contacting sulfur dioxide gas containing impurities with sulfuric acid solutions having a temperature difference. In the examples of Patent Document 1, sulfur dioxide gas with a moisture concentration of 1 mg / kg (3.6 ppm by volume) is produced. However, Patent Document 1 does not disclose the moisture concentration of sulfur dioxide gas required to inhibit metal corrosion, and therefore, using the technology disclosed in Patent Document 1, it was difficult to provide sulfur dioxide capable of inhibiting metal corrosion in a form filled in a filled container so that both a gas phase and a liquid phase exist. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-66962 Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide a sulfur dioxide mixture that is less corrosive to metals and a method for producing the same. Another object of the present invention is to provide a container filled with a sulfur dioxide mixture that is less corrosive to metals. [Means for solving the problem]

[0009] In order to solve the above problems, one aspect of the present invention is as follows [1] to

[11] . [1] A sulfur dioxide mixture containing sulfur dioxide and water, filled in a filled container so that a gas phase and a liquid phase exist, and the water concentration of the gas phase is 0.005 molar ppm or more but less than 5000 molar ppm. [2] A sulfur dioxide mixture containing sulfur dioxide and water, filled in a container so that a gas phase and a liquid phase exist, and the water concentration of the liquid phase is 0.01 molar ppm or more but less than 50 molar ppm. [3] A sulfur dioxide mixture according to [1] or [2], wherein the ratio V / G0 of the internal volume V (unit: L) of the filling container to the initial filling amount G0 (unit: kg) of the sulfur dioxide mixture in the filling container is 0.80 or more and 2.00 or less.

[0010] [4] A method for producing a sulfur dioxide mixture containing sulfur dioxide and water, comprising: a dehydration step of contacting a sulfur dioxide mixture having a water concentration of 500 mol ppm or more with a water adsorbent to reduce the water concentration to less than 50 mol ppm; a filling step of filling the sulfur dioxide mixture obtained in the dehydration step into a filling container so that a gas phase and a liquid phase exist and the water concentration of the liquid phase upon completion of filling is 0.01 mol ppm or more but less than 50 mol ppm; A method for producing a sulfur dioxide mixture comprising:

[0011] [5] The method for producing a sulfur dioxide mixture according to [4], wherein at least a portion of the filling vessel is made of stainless steel. [6] A method for producing a sulfur dioxide mixture described in [4] or [5], wherein the ratio V / G1 of the amount G1 (unit: kg) of the sulfur dioxide mixture filled into the filling container in the filling step to the internal volume V (unit: L) of the filling container is 0.80 or more and 115 or less.

[0012] [7] A filled container filled with a sulfur dioxide mixture containing sulfur dioxide and water, wherein the sulfur dioxide mixture is filled to form a gas phase and a liquid phase, and the water concentration of the gas phase is 0.005 molar ppm or more and less than 5000 molar ppm. [8] A filled container filled with a sulfur dioxide mixture containing sulfur dioxide and water, wherein the sulfur dioxide mixture is filled to form a gas phase and a liquid phase, and the water concentration of the liquid phase is 0.01 molar ppm or more and less than 50 molar ppm.

[0013] [9] A filled container according to [7] or [8], wherein the ratio V / G0 of the internal volume V (unit: L) to the initial filling amount G0 (unit: kg) of the sulfur dioxide mixture is 0.80 or more and 2.00 or less.

[10] The filled container according to any one of [7] to [9], having a capacity of 1 L or more and 2000 L or less.

[11] A filled container according to any one of [7] to

[10] , at least a portion of which is made of stainless steel. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a sulfur dioxide mixture that is less corrosive to metals. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention specifies the water concentration in a sulfur dioxide mixture in order to suppress metal corrosion caused by sulfur dioxide. It is generally known that metal corrosion caused by sulfur dioxide is strongly affected by water concentration, but the effect of water concentration at the ppm level has not been clarified.

[0016] Therefore, the present inventors have conducted extensive research into metal corrosion caused by trace amounts of water in sulfur dioxide and have surprisingly found that metal corrosion is significantly suppressed when the water concentration is sufficiently low, at the ppm level, thereby completing the present invention. One embodiment of the present invention will now be described in detail.

[0017] The sulfur dioxide mixture of this embodiment contains sulfur dioxide and water. The filled container of this embodiment is a filled container filled with the sulfur dioxide mixture. The sulfur dioxide mixture is filled into the filled container so as to form a gas phase and a liquid phase, and the water concentration of the gas phase is 0.005 mol ppm or more and less than 5000 mol ppm.

[0018] By maintaining the moisture concentration of the gas phase within the above range, corrosion of metals used in piping, etc. can be suppressed. Furthermore, by maintaining the moisture concentration of the liquid phase at the time when the sulfur dioxide mixture is completely filled into the filled container at 0.01 mol ppm or more and less than 50 mol ppm, the moisture concentration of the gas phase can be maintained within the above range. Even if the moisture concentration of the liquid phase increases as the sulfur dioxide mixture gas in the filled container is released, if the moisture concentration of the liquid phase of the sulfur dioxide mixture is within the above range, the moisture concentration of the gas phase can be easily maintained within the above range, and corrosion of the metal can be suppressed.

[0019] That is, the product is constituted by the filling container and the sulfur dioxide mixture, and this sulfur dioxide mixture contains sulfur dioxide and water. The sulfur dioxide mixture is filled into the filling container so as to form a gas phase and a liquid phase, and the water concentration of the gas phase is 0.005 molar ppm or more and less than 5000 molar ppm, and to achieve this, the water concentration of the liquid phase at the time of completion of filling is 0.01 molar ppm or more and less than 50 molar ppm. Furthermore, at least a portion of the filling container may be made of stainless steel.

[0020] The moisture concentration in the gas phase mentioned above is the moisture concentration from the time when the sulfur dioxide mixture is completely filled into the filled container to the time when almost the entire amount of the sulfur dioxide mixture in the filled container is released. During this time, the moisture concentration in the gas phase of the sulfur dioxide mixture in the filled container gradually increases within the above range due to the release of the sulfur dioxide mixture gas.

[0021] In addition, when the water concentration of the gas phase of a sulfur dioxide mixture in which both gas and liquid phases coexist is less than 0.01 mol ppm, it is difficult to measure the water concentration directly, so the water concentration of the gas phase is considered to be half the water concentration of the liquid phase. This is based on the fact that the inventors have experimentally confirmed that the water concentrations in a sulfur dioxide mixture in which both gas and liquid phases coexist are in the ratio of gas phase water concentration to liquid phase water concentration = 1:2.

[0022] Such a sulfur dioxide mixture has an extremely low water concentration in the liquid phase when the filling container is completed, so even if water is concentrated in the liquid phase as the vaporized sulfur dioxide mixture gas is released from the filling container, the water concentration in the liquid phase is maintained at a sufficiently low level until the entire amount of the liquefied sulfur dioxide mixture in the filling container is vaporized. Therefore, the water concentration of the sulfur dioxide mixture gas released from the filling container is sufficiently low from the initial stage of release to the final stage of release (the time when the entire amount of the liquefied sulfur dioxide mixture in the filling container is gasified). Therefore, corrosion of metals caused by the sulfur dioxide mixture gas released from the filling container can be significantly suppressed until the final stage of release.

[0023] The water concentration in the liquid phase upon completion of filling into the filling container is 0.01 mol ppm or more and less than 50 mol ppm, preferably 0.01 mol ppm or more and 10 mol ppm or less, more preferably 0.01 mol ppm or more and 3.5 mol ppm or less, and even more preferably 0.01 mol ppm or more and 1.0 mol ppm or less.

[0024] Based on the fact that the moisture concentration in the sulfur dioxide mixture in which the gas phase and the liquid phase coexist is 1:2, the moisture concentration in the gas phase upon completion of filling into the filling container is preferably less than 25 molar ppm, more preferably 5 molar ppm or less, even more preferably 1.7 molar ppm or less, and most preferably 0.5 molar ppm or less.

[0025] If the water concentration in the liquid phase is less than 50 mol ppm, even if water is concentrated in the liquid phase as the sulfur dioxide gas mixture is released from the filled container, the water concentration of the sulfur dioxide gas mixture released from the filled container will be maintained at a level (e.g., less than 5000 mol ppm) at which metal corrosion is suppressed until the end of the release. Note that it is difficult to confirm a water concentration lower than 0.01 mol ppm.

[0026] As described above, the sulfur dioxide mixture in the filled container and the sulfur dioxide mixture gas released from the filled container have a low water concentration and are unlikely to corrode metals. Therefore, there is no need to use expensive corrosion-resistant alloys such as Hastelloy (registered trademark) for parts that come into contact with the sulfur dioxide mixture in the filled container and the sulfur dioxide mixture gas released from the filled container, and metals such as stainless steel can be used. For example, parts that come into contact with the sulfur dioxide mixture in the filled container, piping, manufacturing equipment, supply equipment, conveying equipment, reactors, etc. for the sulfur dioxide mixture can be made of metals such as stainless steel. Usable stainless steel types are not particularly limited, but examples include SUS316, SUS316L, SUS304, and SUS304L.

[0027] Furthermore, the initial filling amount G0 (unit: kg) of the sulfur dioxide mixture into the filling container is the filling amount at the completion of the filling process, and is not particularly limited, but may be 40% or more and 100% or less of the upper limit of the mass calculated according to the internal volume V of the filling container, as stipulated in Article 48, Paragraph 4 of the High Pressure Gas Safety Act and Article 22 of the Container Safety Regulations. In other words, the ratio V / G0 of the internal volume V (unit: L) of the filling container to the initial filling amount G0 (unit: kg) of the sulfur dioxide mixture into the filling container is not particularly limited, but may be 0.80 or more and 2.00 or less.

[0028] If the ratio V / G0 is 0.80 or more (i.e., if the initial filling amount G0 of the sulfur dioxide mixture into the filling container is 100% or less of the upper limit of the mass calculated according to the internal volume V of the filling container), the filling of the sulfur dioxide mixture into the filling container will not be overfilled, and it is safe. On the other hand, if the ratio V / G0 is 2.00 or less (i.e., if the initial filling amount G0 of the sulfur dioxide mixture into the filling container is 40% or more of the upper limit of the mass calculated according to the internal volume V of the filling container), the initial filling amount G0 of the sulfur dioxide mixture relative to the internal volume V of the filling container is sufficient, and the efficiency of transporting the sulfur dioxide mixture by the filling container is high. The ratio V / G0 of the internal volume V (unit: L) of the filling container to the initial filling amount G0 (unit: kg) of the sulfur dioxide mixture in the filling container is more preferably 1.00 or more and 1.90 or less, and even more preferably 1.10 or more and 1.80 or less.

[0029] Next, one embodiment of a method for producing the above-mentioned sulfur dioxide mixture is described. First, moisture is removed from a sulfur dioxide mixture gas having a moisture concentration of 500 mol ppm or more in a dehydration step to obtain a sulfur dioxide mixture gas having a moisture concentration of less than 50 mol ppm. In the dehydration step, the sulfur dioxide mixture gas having a moisture concentration of 500 mol ppm or more is brought into contact with a moisture adsorbent to dehydrate it, thereby reducing the moisture concentration to less than 50 mol ppm.

[0030] As long as the moisture concentration of the sulfur dioxide gas mixture can be reduced to less than 50 mol ppm, the type of moisture adsorbent is not particularly limited, but examples thereof include zeolite, activated carbon, silica gel, and diphosphorus pentoxide. The type of zeolite is also not particularly limited, and the ratio of silica to alumina contained in the zeolite and the pore size of the pores are also not particularly limited, but those that are resistant to sulfur dioxide are preferred, such as molecular sieve 3A and high-silica zeolite.

[0031] The sulfur dioxide gas mixture, the water concentration of which has been reduced to less than 50 mol ppm by the dehydration step, is compressed and partially liquefied in the filling step, and filled into a filling container having a capacity of, for example, 1 L to 2000 L. At this time, the sulfur dioxide gas mixture is compressed and filled so that a portion of the sulfur dioxide gas mixture becomes liquid and the water concentration of the liquid phase upon completion of filling is 0.01 mol ppm to less than 50 mol ppm.

[0032] The method for compressing the sulfur dioxide mixture gas and filling it into a filling container is not limited, but an example is a method in which the sulfur dioxide mixture gas is pressurized using a compressor to liquefy it, and then low-boiling point components and high-boiling point components are removed using a distillation column, and the liquefied sulfur dioxide mixture gas is stored in a product tank and then transferred from the product tank to a filling container for filling.

[0033] The capacity of the filled container can be from 1 L to 2000 L, preferably from 2 L to 1800 L, and more preferably from 3 L to 1500 L. If the capacity of the filled container is 1 L or more, a large amount of sulfur dioxide mixture can be used, resulting in excellent efficiency. On the other hand, if the capacity of the filled container is 2000 L or less, the filled container can be easily manufactured and transported.

[0034] Furthermore, when filling the sulfur dioxide mixture into the filling container, the temperature of the filling container is not particularly limited, but the filling container may be cooled in advance to a temperature of −90° C. or higher and 0° C. or lower. Furthermore, if moisture remains in the filling container, the moisture concentration of the filled sulfur dioxide mixture will increase, so the filling container may be subjected to a heating and decompression treatment in advance so that the amount of remaining moisture in the filling container is 0.1 mol ppm or less.

[0035] Furthermore, the ratio V / G1 of the amount G1 (unit: kg) of the sulfur dioxide mixture filled into the filling container to the internal volume V (unit: L) of the filling container in the filling process is not particularly limited, but may be 0.80 or more and 115 or less. If the ratio V / G1 is 0.80 or more, the filling of the sulfur dioxide mixture into the filling container will not be overfilled, so it is safe. On the other hand, if the ratio V / G1 is 115 or less, the sulfur dioxide mixture is likely to liquefy. The ratio V / G1 of the amount G1 (unit: kg) of the sulfur dioxide mixture filled into the filling container in the filling process to the internal volume V (unit: L) of the filling container is more preferably 1.00 or more and 1.90 or less, and even more preferably 1.10 or more and 1.80 or less.

[0036] Furthermore, the method for measuring the water concentration of the sulfur dioxide mixture in each step (dehydration step, filling step) of the method for producing a sulfur dioxide mixture of this embodiment is not particularly limited as long as it is a method that can accurately measure the water concentration to about 0.01 mol ppm. Examples include methods using a chilled mirror dew point meter, a Fourier transform infrared spectrophotometer (FT-IR), a phosphorus pentoxide moisture meter, or cavity ring-down spectroscopy (CRDS).

[0037] In the present invention, the moisture concentration in the gas phase is measured by taking a sample from the gas phase portion of the filled container and measuring it by cavity ring-down spectroscopy, whereas in the liquid phase, the sample is taken from the liquid phase portion of the filled container, gasified, and measured by cavity ring-down spectroscopy in the same way as in the gas phase case.

[0038] According to the method for producing a sulfur dioxide mixture of this embodiment, a sulfur dioxide mixture having an extremely low water concentration and which is less likely to corrode metals such as stainless steel can be produced using simple equipment. The sulfur dioxide mixture produced by the method for producing a sulfur dioxide mixture of this embodiment can be used as an additive gas to an etching gas used in etching in the manufacturing process of semiconductors and thin film transistors, or as an interface treatment gas.

[0039] Furthermore, the sulfur dioxide mixture obtained by the method for producing a sulfur dioxide mixture of this embodiment can also be used in the production of various chemicals such as pharmaceuticals and dye intermediates. It should be noted that the present embodiment shows only an example of the present invention, and the present invention is not limited to this embodiment. Furthermore, various modifications and improvements can be made to the present embodiment, and such modifications and improvements can also be included in the present invention. [Example]

[0040] The present invention will be described in more detail below with reference to examples and comparative examples. Example 1 30 kg of a sulfur dioxide mixture containing sulfur dioxide and water was filled into a 47 L container at a pressure of 0.23 MPaG (gauge pressure) so that a portion of the mixture was liquid. The ratio V / G0 of the internal volume V of the container to the initial filling amount G0 was 1.57. The sulfur dioxide mixture in the container was separated into a gas phase and a liquid phase, and the water concentration in the liquid phase at the completion of filling was 40 mol ppm.

[0041] The gas phase was extracted from the filled container at a rate of 2 L / min until the remaining amount of the sulfur dioxide mixture in the filled container was 0.4 kg. At this stage, the liquid phase in the filled container disappeared, the entire amount of the sulfur dioxide mixture was gasified, and the moisture concentration of the sulfur dioxide mixture gas in the filled container was 4000 mol ppm. In other words, it can be considered that the moisture concentration of the gas phase of the sulfur dioxide mixture was 4000 mol ppm or less while a portion of the sulfur dioxide mixture was in liquid phase.

[0042] A rectangular test piece (10 mm wide, 50 mm long, 1 mm thick) made of SUS316L was prepared, its mass was measured, and then it was hung in a pressure vessel using a Teflon (registered trademark) string. The above-mentioned sulfur dioxide gas mixture with a water concentration of 4000 mol ppm was introduced into this pressure vessel, and the internal pressure was set to 0.15 MPaG (gauge pressure).

[0043] The pressure vessel was heated to 100°C and left for 5 days. After thoroughly purging with N2 gas and confirming that the sulfur dioxide concentration was less than 0.1 mol ppm, the pressure vessel was opened and the test piece was removed. The removed test piece was ultrasonically cleaned in ultrapure water and 10% by mass nitric acid aqueous solution for 10 minutes each, dried, and then its mass was measured. The corrosion rate was calculated from the change in mass. The resulting corrosion rate was 0.93 μm / y. Thus, even when 98% of the initial charge amount G0 was released, the corrosion caused by the remaining sulfur dioxide mixture gas progressed very slowly.

[0044] Example 2 The same procedure as in Example 1 was carried out, except that the water concentration in the liquid phase at the completion of filling into the filling container was 9.5 mol ppm, and the gas phase was extracted until the liquid phase of the sulfur dioxide mixture in the filling container disappeared, i.e., until the remaining amount was 0.4 kg, resulting in a sulfur dioxide mixture gas with a water concentration in the gas phase of 950 mol ppm. The same procedure as in Example 1 was carried out, except that this sulfur dioxide mixture gas was used, and the corrosion rate of the test piece was measured, which was 0.72 μm / y.

[0045] [Examples 3 and 4, Comparative Examples 1 and 2] In Examples 3 and 4 and Comparative Examples 1 and 2, the corrosion rates of the test pieces were measured in the same manner as in Example 2, except that the "water concentration in the liquid phase at the completion of filling" and the "water concentration in the gas phase after the gas phase was extracted until the remaining amount was 0.4 kg" were set to the values ​​shown in Table 1. The results are shown in Table 1.

[0046] These results (see Table 1) show that if the water concentration in the liquid phase at the completion of filling into the filling container is less than 50 mol ppm, the water concentration in the sulfur dioxide mixture gas released from the filling container will be sufficiently low until the end of the release (the time when all of the liquefied sulfur dioxide mixture in the filling container is gasified), thereby significantly suppressing metal corrosion.

[0047] [Table 1]

[0048] Example 5 Next, an example of a method for producing a sulfur dioxide mixture having a water concentration of less than 50 mol ppm in the liquid phase is shown. 30 kg of crude sulfur dioxide mixture gas having a water concentration of 500 mol ppm is added to 320 m 3 The water was sent to a moisture adsorption tower (volume 320 L) at a flow rate of 1 / h and dehydrated by contacting it with 260 kg of moisture adsorbent (molecular sieve 3A manufactured by Union Showa Co., Ltd.) packed in the moisture adsorption tower.

[0049] The flow rate of the crude sulfur dioxide gas mixture was 10 m / min in linear velocity (LV) and 1000 / h in space velocity (SV). The moisture concentration of the sulfur dioxide gas mixture at the outlet of the moisture adsorption tower was 4.2 mol ppm. 30 kg of this sulfur dioxide gas mixture with a water concentration of 4.2 mol ppm was pressurized to approximately 0.23 MPaG (gauge pressure) using a pump and filled into a 47 L container. The water concentration of the liquefied sulfur dioxide mixture (liquid phase) in the container was 5.8 mol ppm.

Claims

1. A sulfur dioxide mixture containing sulfur dioxide and water, filled in a filled container so that a gas phase and a liquid phase exist, and the water concentration of the gas phase is 0.005 molar ppm or more and less than 5000 molar ppm.

2. A sulfur dioxide mixture containing sulfur dioxide and water, filled in a filled container so that a gas phase and a liquid phase exist, and the water concentration of the liquid phase is 0.01 molar ppm or more and less than 50 molar ppm.

3. The initial charge G of the sulfur dioxide mixture into the charging container ０ The ratio V / G of the internal volume V (unit: L) of the filled container to the mass (unit: kg) ０ The sulfur dioxide mixture according to claim 1 or 2, wherein the sulphur dioxide content is 0.80 or more and 2.00 or less.

4. 1. A method for producing a sulfur dioxide mixture containing sulfur dioxide and water, comprising: a dehydration step of contacting a sulfur dioxide mixture having a water concentration of 500 mol ppm or more with a water adsorbent to reduce the water concentration to less than 50 mol ppm; a filling step of filling the sulfur dioxide mixture obtained in the dehydration step into a filling container so that a gas phase and a liquid phase exist and the water concentration of the liquid phase upon completion of filling is 0.01 mol ppm or more and less than 50 mol ppm; A method for producing a sulfur dioxide mixture comprising:

5. 5. The method of claim 4, wherein at least a portion of said fill vessel is constructed of stainless steel.

6. The amount G of the sulfur dioxide mixture filled into the filling container in the filling step １ The ratio V / G of the internal volume V (unit: L) of the filled container to the mass (unit: kg) １ The method for producing a sulfur dioxide mixture according to claim 4 or 5, wherein the value of the saturation temperature is 0.80 or more and 115 or less.

7. A filled container filled with a sulfur dioxide mixture containing sulfur dioxide and water, wherein the sulfur dioxide mixture is filled so as to form a gas phase and a liquid phase, and the water concentration of the gas phase is 0.005 molar ppm or more and less than 5000 molar ppm.

8. A filled container filled with a sulfur dioxide mixture containing sulfur dioxide and water, wherein the sulfur dioxide mixture is filled so as to form a gas phase and a liquid phase, and the water concentration of the liquid phase is 0.01 molar ppm or more and less than 50 molar ppm.

9. The initial charge amount G of the sulfur dioxide mixture ０ Ratio of internal volume V (unit: L) to internal volume V (unit: kg) V / G ０ 9. The filled container according to claim 7 or 8, wherein the value of the viscosity is 0.80 or more and 2.00 or less.

10. The filled container according to any one of claims 7 to 9, having a capacity of 1 L or more and 2000 L or less.

11. 11. A filled container according to any one of claims 7 to 10, at least a portion of which is made of stainless steel.

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