Cleaning method of high-pressure gas container

Abstract

Provided is a method for cleaning a high-pressure gas container capable of suppressing the generation of water inside the high-pressure gas container. This method for cleaning a high-pressure gas container is provided with: a pressure storage and purification step for purifying the inside of the high-pressure gas container; and a cleaning step for cleaning the inside of the high-pressure gas container after the pressure storage and purification step. The pressure accumulation purification step includes a pressure reduction step in which the interior of the high-pressure gas container is in a reduced pressure state, and an inert gas supply step in which an inert gas is supplied to the high-pressure gas container. The cleaning step is provided with: a hydrogen halide supply step for supplying hydrogen halide to the high-pressure gas container after the pressure accumulation purification step; a metal oxide removal step for generating water by reacting the metal oxide present on the inner surface of the high-pressure gas container with the hydrogen halide inside the high-pressure gas container after the hydrogen halide supply step; and a discharge step of discharging the water and hydrogen halide generated in the metal oxide removal step from the high-pressure gas container.

Description

Technical Field

[0001] This disclosure relates to a method for cleaning high-pressure gas containers. Background Technology

[0002] The hydrogen halide (HX) used in semiconductor manufacturing processes is preferably anhydrous, with a moisture concentration, for example, required to be below 1.0 ppm by volume. However, if a metal oxide (e.g., ferrous oxide (FeO)) is present on the inner surface of the high-pressure gas container filled with hydrogen halide, the filled hydrogen halide reacts with the metal oxide to generate a metal halide (e.g., ferrous chloride (FeCl2)) and water (H2O).

[0003] As a method for removing metal oxides present on the inner surface of a high-pressure gas container, the traditional approach is to react hydrogen halides with the metal oxides. For example, Patent Document 1 discloses a method in which liquefied hydrogen chloride is supplied to the high-pressure gas container, and the metal oxides on the inner surface of the high-pressure gas container react with the liquefied hydrogen chloride at a temperature of 30°C or higher and 50°C or lower to generate water. Subsequently, the liquefied hydrogen chloride containing the generated water is discharged from the high-pressure gas container.

[0004] Existing technical documents

[0005] Patent Document 1: Japanese Patent Publication No. 54799, 2002 Summary of the Invention

[0006] However, the technology disclosed in Patent Document 1, based on the temperature at which the metal oxide on the inner surface of the high-pressure gas container reacts with liquefied hydrogen chloride, may not be able to sufficiently suppress the generation of water, and therefore there is still room for improvement.

[0007] The subject of this disclosure is to provide a cleaning method for high-pressure gas containers that can suppress the generation of water inside the high-pressure gas container.

[0008] In order to solve the aforementioned problem, one aspect of this disclosure is shown in [1] to

[13] below.

[0009] [1] A method for cleaning a high-pressure gas container, comprising: a pressure-accumulating purification step for purifying the interior of the high-pressure gas container, and a cleaning step for cleaning the interior of the high-pressure gas container after the pressure-accumulating purification step.

[0010] The pressure-accumulation purification process includes:

[0011] The decompression stage, which brings the interior of the high-pressure gas container into a decompression state, and

[0012] The inactive gas supply stage involves supplying inactive gas to the high-pressure gas container.

[0013] The cleaning process includes a hydrogen halide supply stage, a metal oxide removal stage, and a discharge stage.

[0014] The hydrogen halide supply stage is the process of supplying hydrogen halide to the high-pressure gas container after the pressure storage and purification process.

[0015] The metal oxide removal stage is a process performed inside the high-pressure gas container after the hydrogen halide supply stage, whereby the metal oxides present on the inner surface of the high-pressure gas container react with the hydrogen halide supplied during the hydrogen halide supply stage to generate water.

[0016] The discharge stage is the process of discharging the water generated in the metal oxide removal stage and the hydrogen halide supplied through the hydrogen halide supply stage from the high-pressure gas container.

[0017] [2] According to the cleaning method of the high-pressure gas container described in [1], no coating material is applied to the inner surface of the high-pressure gas container, and the maximum height Rz of the inner surface of the main body of the high-pressure gas container is less than 5 μm.

[0018] [3] According to the cleaning method of the high-pressure gas container described in [1] or [2], the decompression stage of the pressure accumulating purification process is to exhaust gas while keeping the high-pressure gas container at a temperature below 50°C until the internal pressure becomes below 5Pa, and the inactive gas supply stage of the pressure accumulating purification process is to supply the high-pressure gas container with an inactive gas having a water concentration of less than 0.1 ppm until the internal pressure becomes above 0.1 MPa.

[0019] [4] The pressure accumulator purification process is repeated more than twice according to the cleaning method of the high-pressure gas container according to any one of [1] to [3].

[0020] [5] The cleaning method for the high-pressure gas container according to any one of [1] to [4], wherein the hydrogen halide is at least one of hydrogen fluoride, hydrogen chloride, hydrogen bromide and hydrogen iodide.

[0021] [6] The cleaning method for a high-pressure gas container according to any one of [1] to [5], wherein the hydrogen halide supply stage is a process of supplying hydrogen halide to the high-pressure gas container until the hydrogen halide is liquefied in the high-pressure gas container.

[0022] [7] The cleaning method for the high-pressure gas container according to any one of [1] to [6], wherein the metal oxide removal stage is a process of letting the high-pressure gas container, after being supplied with hydrogen halide through the hydrogen halide supply stage, stand at a temperature below 30°C for more than one day.

[0023] [8] The cleaning method for a high-pressure gas container according to any one of [1] to [7], wherein the volume of the high-pressure gas container is 10L or more and 50L or less, the discharge stage is a process of discharging the water and the hydrogen halide from the high-pressure gas container by inverting the high-pressure gas container upside down.

[0024] [9] The cleaning method for a high-pressure gas container according to any one of [1] to [7], wherein the volume of the high-pressure gas container is more than 50L and less than 1000L, the discharge stage is a process of inserting an inner tube into the interior of the high-pressure gas container and using the inner tube to discharge the liquid phase of the water and the hydrogen halide from the high-pressure gas container.

[0025]

[10] The cleaning method for a high-pressure gas container according to any one of [1] to [7], in the case where the volume of the high-pressure gas container is more than 1000L and less than 1500L, and two or more of the high-pressure gas containers are connected in parallel by a manifold to form a module, the discharge stage is a process of inserting an inner tube into the interior of the two or more high-pressure gas containers respectively, and using the inner tube to discharge the liquid phase water and the hydrogen halide from the two or more high-pressure gas containers respectively through the manifold.

[0026]

[11] According to the cleaning method of the high-pressure gas container described in

[10] , the manifold is connected only to one side of the two or more high-pressure gas containers, or to both sides respectively.

[0027]

[12] The cleaning method for the high-pressure gas container according to any one of [1] to

[11] shall be performed more than twice after the pressure accumulating and purification process.

[0028]

[13] The cleaning method for the high-pressure gas container according to any one of [1] to

[12] , wherein the metal oxide is at least one of iron oxide, chromium oxide, molybdenum oxide and manganese oxide.

[0029] If the interior of a high-pressure gas container is cleaned using the cleaning method disclosed herein, the generation of water inside the high-pressure gas container can be suppressed. Attached Figure Description

[0030] Figure 1 This is a schematic diagram illustrating an example of an apparatus for performing a hydrogen halide supply stage and a discharge stage in a high-pressure gas container cleaning method according to an embodiment of the present disclosure.

[0031] Figure 2 This is a schematic diagram illustrating an example of an apparatus for performing a pressure-accumulating purification step in a high-pressure gas container cleaning method according to an embodiment of the present disclosure.

[0032] Figure 3 This is a cross-sectional view showing an example of a high-pressure gas container that can be used in the cleaning method for a high-pressure gas container according to an embodiment of the present disclosure.

[0033] Figure 4 This is a cross-sectional view showing an example of a high-pressure gas container that can be used in the cleaning method for a high-pressure gas container according to an embodiment of the present disclosure.

[0034] Figure 5 These are plan and front views of a module body showing an example of a high-pressure gas container that can be used in a cleaning method for a high-pressure gas container according to an embodiment of the present disclosure. Detailed Implementation

[0035] The following describes one embodiment of this disclosure. Furthermore, this embodiment illustrates one example of this disclosure, and this disclosure is not limited to this embodiment. In addition, various modifications or improvements can be made to this embodiment, and such modifications or improvements are also included in this disclosure.

[0036] The high-pressure gas container cleaning method of this embodiment includes: a pressure-accumulating purification step for purifying the interior of the high-pressure gas container, and a cleaning step for cleaning the interior of the high-pressure gas container after the pressure-accumulating purification step. The pressure-accumulating purification step includes: a decompression stage for bringing the interior of the high-pressure gas container to a decompression state, and an inactive gas supply stage for supplying an inactive gas to the high-pressure gas container. The cleaning step includes a hydrogen halide supply stage, a metal oxide removal stage, and a discharge stage. The hydrogen halide supply stage is a step of supplying hydrogen halide to the high-pressure gas container after the pressure-accumulating purification step. The metal oxide removal stage is a step of reacting the metal oxides present on the inner surface of the high-pressure gas container with the hydrogen halide supplied through the hydrogen halide supply stage to generate water inside the high-pressure gas container after the hydrogen halide supply stage. The discharge stage is a step of discharging the water generated in the metal oxide removal stage and the hydrogen halide supplied through the hydrogen halide supply stage from the high-pressure gas container.

[0037] The cleaning method for a high-pressure gas container according to this embodiment includes: a pressure-accumulating purification process for purifying the interior of the high-pressure gas container, and a cleaning process for cleaning the interior of the high-pressure gas container after the pressure-accumulating purification process.

[0038] The pressure accumulator purification process includes a depressurization stage and a non-reactive gas supply stage. The depressurization stage is the process of bringing the interior of the high-pressure gas container to a reduced pressure state. The non-reactive gas supply stage is the process of supplying non-reactive gas to the high-pressure gas container.

[0039] The cleaning process comprises a hydrogen halide supply stage, a metal oxide removal stage, and a discharge stage. The hydrogen halide supply stage involves supplying hydrogen halide into the high-pressure gas container after the pressurization and purification process. The metal oxide removal stage occurs inside the high-pressure gas container after the hydrogen halide supply stage, where the metal oxides present on the inner surface of the container react with the hydrogen halide supplied in the hydrogen halide supply stage to generate water. The discharge stage involves discharging the water generated in the metal oxide removal stage and the hydrogen halide supplied in the hydrogen halide supply stage from the high-pressure gas container.

[0040] The high-pressure gas container cleaning method of this embodiment includes the above-described pressure accumulator purification step and the above-described cleaning step. Therefore, if the high-pressure gas container is cleaned using the high-pressure gas container cleaning method of this embodiment, the metal oxides that are the source of water generation are removed, and the generation of water inside the high-pressure gas container can be suppressed.

[0041] This high-pressure gas container cleaning method of the present embodiment is suitable for cleaning high-pressure gas containers used for filling and storing hydrogen halides in semiconductor manufacturing processes. Since water is less likely to form inside the high-pressure gas container cleaned by the method of the present embodiment, the moisture concentration of the filled hydrogen halides can be maintained at a low concentration (e.g., below 1.0 ppm by volume). In other words, using a high-pressure gas container cleaned by the method of the present embodiment yields high-quality hydrogen halides.

[0042] Furthermore, there are limitations on the concentration of hydrogen molecules (H2) in hydrogen halides used in semiconductor manufacturing processes, for example, requiring it to be reduced to below 10 ppm by volume. However, it is known that ferrous chloride and hydrogen molecules are generated by reacting hydrogen halides with a zero-valent metal (e.g., iron) present on the inner surface of a high-pressure gas container. The hydrogen molecule generation reaction is endothermic and therefore proceeds readily as the reaction temperature increases. Therefore, there is a concern that the method described in, for example, Patent Document 1, which involves heating the high-pressure gas container supplied with hydrogen halides, might promote the generation of hydrogen molecules.

[0043] The high-pressure gas container cleaning method of this embodiment does not require heating the high-pressure gas container supplied with hydrogen halide, thus suppressing the generation of hydrogen molecules. Therefore, it can suppress the deterioration of the hydrogen molecule concentration in hydrogen halide and maintain it below 10 ppm by volume.

[0044] As high-pressure gas containers become larger, heat treatment of these containers becomes difficult to implement. However, the cleaning method for high-pressure gas containers in this embodiment does not require heat treatment and can remove metal oxides from the interior of the high-pressure gas container under mild conditions.

[0045] Furthermore, the high-pressure gas container cleaned by the high-pressure gas container cleaning method of this embodiment can be filled and stored with various gases, not limited to hydrogen halides.

[0046] The cleaning method for the high-pressure gas container of this embodiment will be described in more detail below.

[0047] [High-pressure gas container]

[0048] The high-pressure gas container used in the high-pressure gas container cleaning method of this embodiment is a container that releases and fills gas through a gas flow path. The type of high-pressure gas container used in the high-pressure gas container cleaning method of this embodiment is not particularly limited; for example, its size and shape are not particularly limited. The material of the high-pressure gas container is also not particularly limited; examples include metallic materials containing at least one of iron (Fe), chromium (Cr), molybdenum (Mo), and manganese (Mn).

[0049] Furthermore, the high-pressure gas container used in the cleaning method of the high-pressure gas container in this embodiment can be a new (unused) high-pressure gas container or a used high-pressure gas container. Moreover, it can be a high-pressure gas container open to the atmosphere or a high-pressure gas container not open to the atmosphere.

[0050] There are no particular restrictions on the condition of the inner surface of the high-pressure gas container. The inner surface of the high-pressure gas container may be coated with a coating material or may not be coated. Examples of coating materials that can be applied to the inner surface of a high-pressure gas container include nickel (Ni) plating, nickel-phosphorus alloy (Ni-P) plating, zinc (Zn) plating, gold (Au) plating, and silver (Ag) plating.

[0051] Furthermore, the roughness of the inner surface of the high-pressure gas container is not particularly limited, but the maximum height Rz of the inner surface of the main body of the high-pressure gas container is preferably 5 μm or less. It is also possible to omit the coating material from the inner surface of the high-pressure gas container, and the maximum height Rz of the inner surface of the main body of the high-pressure gas container is 5 μm or less. If the roughness (smoothness) of the inner surface of the high-pressure gas container is small, the quality of the hydrogen halide filled after cleaning can be maintained at a high quality even with a simplified cleaning method. In addition, compared with conventional cleaning methods for high-pressure gas containers, the quality of the hydrogen halide can be improved.

[0052] More preferably, the maximum height Rz of the inner surface of the main body of the high-pressure gas container is 1 μm or more and 5 μm or less, and the maximum height Rz of the inner surface of the portion other than the main body of the high-pressure gas container is 15 μm or more and 20 μm or less. More preferably, the maximum height Rz of the inner surface of the main body of the high-pressure gas container is 1 μm or less, and the maximum height Rz of the inner surface of the portion other than the main body of the high-pressure gas container is 15 μm or more and 20 μm or less. Particularly preferably, the maximum height Rz of the inner surface of the main body of the high-pressure gas container is 1 μm or less, and the maximum height Rz of the inner surface of the portion other than the main body of the high-pressure gas container is 1 μm or less.

[0053] Furthermore, the "main body" of the high-pressure gas container in this disclosure refers to the central portion along the long axis of the high-pressure gas container, excluding the two ends along the long axis. Moreover, the ends are portions having a volume of 5% of the volume of the high-pressure gas container.

[0054] For example, when the high-pressure gas container is cylindrical or square, the main body refers to the central portion of the cylinder or square, excluding the two ends in the height direction (length direction). Conversely, when the high-pressure gas container is spherical, the main body refers to the central portion excluding the two ends in the radial direction of the sphere.

[0055] There is no particular limitation on the method for reducing the maximum height Rz of the inner surface of the main body of the high-pressure gas container; methods such as grinding the inner surface of the main body of the high-pressure gas container can be cited. Examples of methods for grinding the inner surface of the main body of the high-pressure gas container include sandblasting, tumbling, and electrolytic grinding.

[0056] There are no particular limitations on the method for measuring the maximum height Rz of the inner surface of the main body of the high-pressure gas container. For example, the method described in Japanese Industrial Standard JIS B0601-2013 can be used.

[0057] There are no particular limitations on the measuring machine used to measure the maximum height Rz of the inner surface of the main body of a high-pressure gas container. For example, a stylus-type surface roughness measuring machine such as the SURFTEST SJ-210 series small surface roughness measuring machine manufactured by Mitutoyo Corporation can be used.

[0058] Furthermore, the cleaning method for high-pressure gas containers of this embodiment can be applied to the cleaning of various high-pressure gas containers, but it is particularly suitable for cleaning high-pressure gas containers where no coating material is applied to the inner surface and the maximum height Rz of the inner surface of the main body is less than 5 μm.

[0059] Next, refer to Figures 1-4 This illustrates an example of the cleaning method for the high-pressure gas container according to this embodiment.

[0060] [Pressure accumulator purification process]

[0061] High-pressure gas containers used in the cleaning process require a pressure purification process to remove internal water beforehand.

[0062] The pressure accumulator purification process includes a decompression stage to bring the interior of the high-pressure gas container to a reduced pressure state, and an inactive gas supply stage to supply inactive gas to the high-pressure gas container. However, the order of the decompression stage and the inactive gas supply stage is not particularly limited. That is, the inactive gas supply stage can be performed after the decompression stage, or the decompression stage can be performed after the inactive gas supply stage, within the high-pressure gas container where the inactive gas supply stage has already been performed. In other words, the pressure accumulator purification process is a process where one of the decompression stage and the inactive gas supply stage is performed before the other.

[0063] If the inactive gas supply stage is performed after the decompression stage, the amount of inactive gas used in the inactive gas supply stage can be reduced. Furthermore, if the pressure-accumulating purification process is repeated more than twice, performing the inactive gas supply stage after the decompression stage allows atmospheric components to be removed from the high-pressure gas container beforehand. Simultaneously, the inactive gas supplied to the high-pressure gas container during the inactive gas supply stage after the decompression stage diffuses more evenly within the high-pressure gas container, making it easier to remove impurities from the high-pressure gas container during the subsequent decompression stage.

[0064] On the other hand, if the decompression stage is performed after the inactive gas supply stage, the time required for the decompression stage can be reduced. That is, when there is a lot of water in the high-pressure gas container, the water is adsorbed on the inner surface of the high-pressure gas container, thus increasing the time required to reach the target vacuum level during the decompression stage. If the decompression stage is performed after the inactive gas supply stage, the water can be discharged from the high-pressure gas container along with the inactive gas, thereby reducing the time required for the decompression stage.

[0065] Furthermore, the "pressure accumulator purification" in this disclosure refers to the following operation: First, an inert gas is supplied to a high-pressure gas container until the pressure inside the container reaches a predetermined pressure. For example, after a certain period of time, the inert gas is discharged from the high-pressure gas container using a vacuum pump, thereby reducing the pressure inside the container to below atmospheric pressure. A specific example of such an operation is the following: Inert gas is supplied to and filled into a high-pressure gas container; when the pressure inside the container reaches a predetermined pressure, the inert gas is discharged from the container, reducing the pressure inside the container to below atmospheric pressure.

[0066] Alternatively, "pressure purification" refers to the following operation: First, for example, a vacuum pump is used to purge the gas from the high-pressure gas container, so that the pressure inside the high-pressure gas container is below atmospheric pressure, and then an inactive gas is supplied into the high-pressure gas container until the pressure inside the high-pressure gas container reaches a predetermined pressure.

[0067] The predetermined pressure mentioned above is not particularly limited; it can be atmospheric pressure (0.1013 MPa), pressure below atmospheric pressure, or pressure above atmospheric pressure.

[0068] Reference Figure 2 The pressure accumulator purification process is explained. Figure 2 This diagram illustrates an example of an apparatus for performing a pressure-accumulating purification process. The following description will illustrate an example of a pressure-accumulating purification process where an inactive gas supply stage follows a depressurization stage.

[0069] First, a depressurization stage is performed to bring the interior of, for example, a 47L high-pressure gas container 19 into a depressurized state. That is, a vacuum pump 17 is used to purge water and other gases from the interior of the high-pressure gas container 19. The depressurization stage is preferably performed while maintaining the high-pressure gas container 19 at a temperature below 50°C. The pressure inside the high-pressure gas container 19 after the depressurization stage is preferably below 5 Pa, more preferably below 1 Pa, and even more preferably below 0.01 Pa. The vacuum pump 17 is preferably a dry vacuum pump.

[0070] Next, an inactive gas supply stage is implemented, in which an inactive gas is supplied to the high-pressure gas container 19 after the decompression stage until the internal pressure reaches a predetermined pressure. The type of inactive gas is not particularly limited, and examples include nitrogen (N2), helium (He), argon (Ar), and xenon (Xe). Figure 2 This is an example of using nitrogen as an inert gas. Furthermore, prior to the implementation of the inert gas supply phase, it is preferable to drain the water in the piping by allowing nitrogen to flow from the nitrogen supply source 13 into the piping.

[0071] The moisture concentration of inactive gases such as nitrogen used in the inactive gas supply stage is preferably 0.5 ppm by volume or less, more preferably 0.1 ppm by volume or less, and even more preferably 0.05 ppm by volume or less.

[0072] Furthermore, the filling pressure when supplying inactive gases such as nitrogen to the high-pressure gas container 19 is preferably 0.1 MPa or more, more preferably 0.5 MPa or more, and even more preferably 1.5 MPa or more.

[0073] The pressure-accumulating purification process can be performed once, but it can also be performed more than twice. That is, the depressurization stage and the inactive gas supply stage can each be performed once, but they can also be performed alternately and repeatedly more than twice.

[0074] Alternatively, the moisture concentration of the nitrogen gas filled into the high-pressure gas container 19 can be measured after the inactive gas supply phase is completed. The moisture concentration of the nitrogen gas can be measured using a moisture meter. As a moisture meter, an analytical device using cavity ring-down spectroscopy (CRDS) can be used.

[0075] The decompression stage of the pressure accumulator purification process can be a process of venting the high-pressure gas container while maintaining it at a temperature below 50°C until the internal pressure becomes below 5Pa. The inactive gas supply stage of the pressure accumulator purification process can be a process of supplying an inactive gas with a moisture concentration of less than 0.1 ppm to the high-pressure gas container until the internal pressure reaches above 0.1 MPa.

[0076] [Cleaning Process]

[0077] After the pressure accumulator purification process is completed, a cleaning process is performed to clean the inside of the high-pressure gas container. Figure 1 This diagram illustrates an example of an apparatus used for the cleaning process. (Refer to...) Figure 1 The cleaning process is described.

[0078] First, after creating a vacuum inside the high-pressure gas container 19 following the pressure storage and purification process, from... Figure 2 Remove from the device shown and install it. Figure 1 On the device shown. Furthermore, in Figure 1 In this document, "high-pressure gas container 19" is referred to as "high-pressure gas container 7". Next, a hydrogen halide supply phase is implemented to supply hydrogen halide to the high-pressure gas container 7; however, before implementing the hydrogen halide supply phase, the following operation is preferably performed. That is, it is preferable to supply hydrogen halide to the high-pressure gas container 7. Figure 1 In the apparatus shown, hydrogen halide is supplied through a piping located upstream of the high-pressure gas container 7. After being pressurized to a pressure of 0.1 MPaG or higher, the pressure is repeatedly reduced to atmospheric pressure using the discharge unit 12 to remove hydrogen halide beforehand. Figure 1 The device shown contains air and water.

[0079] After performing the above operations, the hydrogen halide supply stage is implemented. Preferably, the hydrogen halide supply stage involves supplying hydrogen halide to the high-pressure gas container until it liquefies within the container. That is, hydrogen halide can also be supplied from the hydrogen halide supply source 5 to the high-pressure gas container 7, continuing the supply until the hydrogen halide exists as a two-phase mixture of gas and liquid within the container 7 (until a portion of the hydrogen halide liquefies). The mass of hydrogen halide supplied to the high-pressure gas container 7 can also be measured using a gravimeter. Furthermore, the mass of hydrogen halide supplied to the 47L high-pressure gas container 7 is preferably 5kg or more and 30kg or less.

[0080] There is no particular limitation on the type of hydrogen halide; it can be at least one of hydrogen fluoride (HF), hydrogen chloride (HCl), hydrogen bromide (HBr), and hydrogen iodide (HI). Figure 1 This is an example of using hydrogen chloride as a hydrogen halide.

[0081] Furthermore, the water concentration of the hydrogen halide supplied from the hydrogen halide supply source 5 to the high-pressure gas container 7 is preferably 0.2 ppm by volume or less, more preferably 0.1 ppm by volume or less, and even more preferably 0.05 ppm by volume or less.

[0082] Furthermore, the purity of the hydrogen halide supplied from the hydrogen halide supply source 5 to the high-pressure gas container 7 is preferably 3N or higher (99.9% by volume or higher), more preferably 4N or higher (99.99% by volume or higher), and even more preferably 5N or higher (99.999% by volume or higher).

[0083] Here, it is preferable to place the high-pressure gas container 7, after supplying hydrogen halide, from... Figure 1 Before removing the device shown, Figure 1 Hydrogen halide is removed from the apparatus shown. Specifically, it is preferable to remove it from the purification helium cylinder 1. Figure 1 The device shown is supplied with helium, which will Figure 1 After the device is pressurized to a pressure of 1.0 MPaG or higher, the pressure is repeatedly reduced to atmospheric pressure using the discharge unit 12 to remove pre-existing pressure. Figure 1 Hydrogen halide inside the device shown.

[0084] from Figure 1 The high-pressure gas container 7 is removed from the apparatus shown, and a metal oxide removal stage is performed. That is, inside the high-pressure gas container 7 after the hydrogen halide supply stage, the metal oxides present on the inner surface of the high-pressure gas container 7 react with the hydrogen halide supplied through the hydrogen halide supply stage to generate water.

[0085] There is no particular limitation on the types of metal oxides; at least one of iron oxide, chromium oxide, molybdenum oxide, and manganese oxide can be cited as examples.

[0086] The metal oxide removal stage can be performed by allowing the high-pressure gas container 7, after the hydrogen halide supply stage, to stand at a predetermined temperature for a predetermined time. The temperature during the metal oxide removal stage is preferably below 30°C. Furthermore, the time during the metal oxide removal stage is preferably 1 day or more, more preferably 10 days or more, and even more preferably 60 days or more. That is, the metal oxide removal stage can also be a process of allowing the high-pressure gas container, after being supplied with hydrogen halide in the hydrogen halide supply stage, to stand at a temperature below 30°C for 1 day or more.

[0087] There are no particular limitations on the method of setting the high-pressure gas container 7 to a temperature below 30°C; for example, using air conditioning equipment such as an air conditioner can be cited. Furthermore, during the metal oxide removal stage, it is believed that the room temperature and external air temperature of the environment in which the high-pressure gas container 7 is located will have some influence on the reaction rate of the metal oxides and hydrogen halides, but in the temperature range below 30°C, this influence is negligible. Therefore, in the temperature range below 30°C, the number of cleaning steps required to achieve the necessary cleaning effect will not increase with the temperature. Additionally, during the metal oxide removal stage, the interior of the high-pressure gas container 7 is a sealed space, and therefore is almost unaffected by the humidity and air pressure outside the high-pressure gas container 7.

[0088] Next, the water generated by the reaction of metal oxides and hydrogen halides in the metal oxide removal stage, together with the remaining hydrogen halides supplied by the hydrogen halides supply stage and not consumed in the metal oxide removal stage, is discharged from the high-pressure gas container 7 in the discharge stage. In this discharge stage, metal halides generated by the reaction of metal oxides and hydrogen halides in the metal oxide removal stage may also be discharged from the high-pressure gas container 7.

[0089] use Figure 1 The apparatus shown discharges water and hydrogen halide from the high-pressure gas container 7. However, considering the distribution coefficient of water relative to hydrogen halide, discharging water-containing hydrogen halide from the liquid phase side is more efficient in removing water from the outside of the high-pressure gas container 7 than discharging from the gas phase side.

[0090] Therefore, for example, when the volume of the high-pressure gas container is 10L or more but less than 50L, the preferred discharge stage is a process of discharging water and hydrogen halide from the high-pressure gas container by inverting it vertically. That is, in the case of a small high-pressure gas container with a volume of 10L or more but less than 50L, since it only has one container valve, in order to discharge hydrogen halide from the liquid phase side, it is preferable to install the high-pressure gas container with the container valve facing downwards in the vertical direction, so that the liquefied hydrogen halide can be discharged from the high-pressure gas container.

[0091] Furthermore, small high-pressure gas containers with a volume of 10L or more but less than 50L are preferably installed with the container valve facing downwards in the vertical direction. However, it is not necessary for them to be upright. As long as the container valve faces downwards in the vertical direction, even a tilted position is acceptable. There is no particular limitation on the tilt angle, but for example, it is preferably 45° or more but less than 90°.

[0092] On the other hand, for example, when the volume of the high-pressure gas container exceeds 50L but is less than 1000L, the preferred discharge stage is a process in which an inner tube is inserted inside the high-pressure gas container to discharge liquid water and hydrogen halide from the high-pressure gas container using the inner tube. Figure 3 The 440L high-pressure gas container 24 shown is Figure 4 The high-pressure gas container 32 with a volume of 900L shown has gas-phase side siphons 21 and 28 and liquid-phase side siphons 22 and 29 inserted inside it (the gas-phase side siphons 21 and 28 and the liquid-phase side siphons 22 and 29 are equivalent to internal insertion tubes that are constituent elements of this disclosure). Therefore, by using the downward-facing liquid-phase side siphons 22 and 29, liquefied hydrogen halide can be discharged from the liquid phase side to the outside of the high-pressure gas containers 24 and 32, thus efficiently discharging the water contained in the hydrogen halide to the outside of the high-pressure gas containers 24 and 32.

[0093] Even when two or more high-pressure gas containers are connected side-by-side with manifolds to form a modular body, the liquid phase water and hydrogen halide can be discharged from the high-pressure gas containers using internal insertion tubes in the same manner as described above. That is, when the volume of the high-pressure gas containers exceeds 1000L but is less than 1500L and two or more high-pressure gas containers are connected side-by-side with manifolds to form a modular body, the preferred discharge stage is to insert internal insertion tubes into the interior of each of the two or more high-pressure gas containers, and use the internal insertion tubes to discharge the liquid phase water and hydrogen halide from the two or more high-pressure gas containers separately through the manifolds.

[0094] Reference Figure 5 An example of a cleaning method for the high-pressure gas container forming the module body will be described. First, before filling the high-pressure gas container 34 with hydrogen halide from one of the two manifolds connected to the two ends of each high-pressure gas container 34, the pressure-accumulating purification of said manifold and the filling line (not shown) is performed using an inactive gas.

[0095] After the pressure accumulating purification of one manifold and the filler line (not shown) is completed, all container valves 35 of the high-pressure gas container 34 are set to the open state, and inert gas is used to perform pressure accumulating purification of the high-pressure gas container 34 and the other manifold. When the manifold is only connected to one end of the high-pressure gas container 34, only the container valves 35 separating the manifold and the high-pressure gas container 34 are all opened for pressure accumulating purification. This type of pressure accumulating purification of the module is implemented in the same way as described above, by repeatedly supplying inert gas, pressurizing it, and then depressurizing it to approximately atmospheric pressure.

[0096] Next, the high-pressure gas container 34 is cleaned using hydrogen halide. First, hydrogen halide is supplied to one of the manifolds and a filler line (not shown) until the hydrogen halide is present only in a gaseous phase, or in a state where both gaseous and liquid phases are present. The supply of hydrogen halide can be managed using a pressure gauge 38 mounted on the manifold, or by measuring the change in mass of the high-pressure gas container 34 using a weighted gauge. Then, the hydrogen halide supplied to the high-pressure gas container 34 is blown to a pressure higher than atmospheric pressure. This supply and blowing of hydrogen halide is alternated until a predetermined number of cycles are reached.

[0097] Next, hydrogen halide is supplied to each high-pressure gas container 34 via the manifold of one of the aforementioned entities. The supply of hydrogen halide is the same as described above, preferably continuing until the hydrogen halide is separated into a gaseous and liquid phase within the high-pressure gas container 34 (a portion of the hydrogen halide is liquefied).

[0098] When manifolds are connected to both ends of the high-pressure gas container 34, after supplying hydrogen halide to all the high-pressure gas containers 34 constituting the module body, the cleaning of the other manifold is performed simultaneously with the cleaning of all the high-pressure gas containers 34. That is, the container valve 35 (the container valve connected to the other manifold) of at least one of the high-pressure gas containers 34 to which hydrogen halide has been supplied is opened, hydrogen halide is supplied to the other manifold, and the cleaning of all the high-pressure gas containers 34 and the cleaning of the other manifold are performed simultaneously.

[0099] Furthermore, the cleaning of hydrogen halide in the manifold is arbitrary. Alternatively, only the high-pressure gas container 34 can be cleaned by filling it with hydrogen halide; for the manifold, purification is performed with an inactive gas after filling only the high-pressure gas container 34 with hydrogen halide.

[0100] After the supply of hydrogen halide to all high-pressure gas containers 34 and manifolds is completed, the metal oxide removal stage is performed in the same manner as described above. At this time, the module can be placed in a stationary state or transported while mounted on a base (cart).

[0101] After the metal oxide removal stage is completed, the hydrogen halide in the high-pressure gas container 34 and manifold, along with the generated water and metal halides, is discharged to the outside of the module body. As described above, discharging hydrogen halide from the liquid phase side is more effective in removing impurities such as water to the outside of the high-pressure gas container 34 than discharging hydrogen halide from the gas phase side; therefore, hydrogen halide is discharged via the manifold on the liquid phase side. Furthermore, it is preferable to discharge hydrogen halide separately for each high-pressure gas container 34 to prevent impurities from accumulating in the high-pressure gas container 34 located at the bottom of the module body.

[0102] This cleaning process can be performed once after the pressure-accumulating purification process, or it can be performed more than twice after the pressure-accumulating purification process.

[0103] After the cleaning process is completed, the moisture concentration and hydrogen molecule concentration of the hydrogen halides discharged during the discharge stage can be measured separately. The moisture concentration of the hydrogen halides can be measured using an analytical device employing cavity ring-down spectroscopy. Alternatively, the hydrogen molecule concentration of the hydrogen halides can be measured, for example, using gas chromatography (GC). A pulsed discharge photoionization detector can be used as the detector in the gas chromatography.

[0104] The high-pressure gas container cleaned as described above can be used as a high-pressure gas container for filling and storing hydrogen halides. That is, if hydrogen halides are filled into the high-pressure gas container cleaned as described above, the moisture concentration of the filled hydrogen halides can be maintained at a low concentration (e.g., below 1.0 ppm by volume). The type of hydrogen halides used for filling is not particularly limited and can be at least one of hydrogen fluoride, hydrogen chloride, hydrogen bromide, and hydrogen iodide.

[0105] Example

[0106] The following examples and comparative examples illustrate this disclosure in more detail.

[0107] [Example 1]

[0108] Prepare a 47L metal high-pressure gas container. Grind the inner surface of the high-pressure gas container, setting the maximum height Rz of the inner surface of the main body to 1μm and the maximum height Rz of the inner surface of the parts other than the main body to 20μm. No coating material is applied to the inner surface of the high-pressure gas container.

[0109] Install the high-pressure gas container Figure 2The apparatus shown incorporates a pressure-accumulating purification process. Specifically, it involves a decompression phase where the internal pressure of the high-pressure gas container is reduced to 3 Pa while maintaining a temperature between 15°C and 25°C. This is followed by a non-reactive gas supply phase where nitrogen gas with a moisture concentration below 0.05 ppm (volume) is added to the high-pressure gas container until the internal pressure reaches 0.3 MPa. The decompression and non-reactive gas supply phases are alternately repeated five times each. The moisture concentration of the nitrogen gas filling the high-pressure gas container is determined using a cavity ring-down spectroscopy (CRDS) analyzer, and the result is below 0.1 ppm (volume).

[0110] Next, the high-pressure gas container after the pressure storage and purification process is depressurized under the same conditions as the depressurization stage of the pressure storage and purification process, and then... Figure 2 Remove the high-pressure gas container from the device shown and install it. Figure 1 On the device shown. Then, set the container valve of the high-pressure gas container to the closed state, and... Figure 1 Hydrogen chloride is supplied into the device shown until the pressure reaches 1.80 MPaG, then depressurized until the residual pressure reaches 0.1 MPaG. This operation is repeated a total of 5 times.

[0111] Next, a cleaning process is performed on the high-pressure gas container. Specifically, with the container valve open, 25 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm (volume) is added to the high-pressure gas container (hydrogen halide supply stage). Then, the container is left to stand for 24 hours while maintaining a temperature between 15°C and 25°C (metal oxide removal stage). Afterward, the high-pressure gas container valve is closed, and the process continues... Figure 1 The device shown is removed. The high-pressure gas container is inverted (with the valve facing downwards in the vertical direction), and the valve is opened to discharge hydrogen chloride from the high-pressure gas container until the residual pressure reaches 0.11 MPa (discharge stage). The cleaning process described above is repeated a total of 4 times.

[0112] After the cleaning process, 25 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm (volume) was refilled into the high-pressure gas container. The moisture concentration of the hydrogen chloride in the high-pressure gas container was then determined using a cavity ring-down spectroscopy (CRDS) analyzer, while the hydrogen molecule concentration was determined using gas chromatography (GC). A pulsed discharge photoionization detector was used as the detector for GC. The results showed that the moisture concentration of the hydrogen chloride was 0.6 ppm (volume), and the hydrogen molecule concentration was less than 0.1 ppm (volume). The results are shown in Table 1.

[0113] [Example 2]

[0114] Prepare a 440L metal high-pressure gas container (refer to...) Figure 3 The inner surface of the high-pressure gas container was ground, with the maximum height Rz of the inner surface of the main body set to 1 μm, and the maximum height Rz of the inner surface of the parts other than the main body set to 20 μm. No coating material was applied to the inner surface of the high-pressure gas container.

[0115] The high-pressure gas container was changed from a 47L container to a 440L container as described above, and the pressure-accumulating purification process was performed in the same manner as in Example 1. The pressure-accumulating purification process was repeated twice; that is, the depressurization stage and the inactive gas supply stage were alternately repeated twice. The moisture concentration of the nitrogen gas filled in the high-pressure gas container was determined using a cavity ring-down spectroscopy (CRDS) analyzer, and the result was less than 0.1 ppm by volume.

[0116] Next, the high-pressure gas container after the pressure storage and purification process will be transferred from... Figure 2 Remove the device shown and install it from the container valve side to... Figure 1 On the device shown. Then, set the container valve of the high-pressure gas container to the closed state, and... Figure 1 Hydrogen chloride is supplied into the device shown until the pressure reaches 1.80 MPaG, then depressurized until the residual pressure reaches 0.1 MPaG. This operation is repeated a total of 5 times.

[0117] Next, a cleaning process is performed on the high-pressure gas container. Specifically, with the container valve open, 250 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm (volume) is added to the high-pressure gas container (hydrogen halide supply stage). Then, the container is left to stand for 24 hours while maintaining a temperature between 15°C and 25°C (metal oxide removal stage). Afterward, the container valve is closed, and the gas is then... Figure 1 Remove from the device shown, and discharge hydrogen chloride from the high-pressure gas container via a liquid-phase siphon until the residual pressure reaches 0.11 MPa (discharge stage). The cleaning process is performed once.

[0118] After the cleaning process, 250 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm by volume was refilled into the high-pressure gas container. Then, the moisture concentration and hydrogen molecule concentration of the hydrogen chloride filled into the high-pressure gas container were measured in the same manner as in Example 1. As a result, the moisture concentration of the hydrogen chloride was 0.5 ppm by volume, and the hydrogen molecule concentration of the hydrogen chloride was less than 0.1 ppm by volume. The results are shown in Table 1.

[0119] [Example 3]

[0120] Prepare a 900L metal high-pressure gas container (refer to...) Figure 4The inner surface of the high-pressure gas container was ground, with the maximum height Rz of the inner surface of the main body set to 1 μm, and the maximum height Rz of the inner surface of the parts other than the main body set to 20 μm. No coating material was applied to the inner surface of the high-pressure gas container.

[0121] The high-pressure gas container was changed from a 440L container to a 900L container as described above, and the pressure-accumulating purification process was performed in the same manner as in Example 2. The pressure-accumulating purification process was repeated three times; that is, the depressurization stage and the inactive gas supply stage were alternately repeated three times each. The moisture concentration of the nitrogen gas filled in the high-pressure gas container was determined using a cavity ring-down spectroscopy (CRDS) analyzer, and the result was less than 0.1 ppm by volume.

[0122] Next, the high-pressure gas container after the pressure storage and purification process will be transferred from... Figure 2 Remove the device shown and install it from the container valve side to... Figure 1 On the device shown. Then, set the container valve of the high-pressure gas container to the closed state, and... Figure 1 Hydrogen chloride is supplied into the device shown until the pressure reaches 1.80 MPaG, then depressurized until the residual pressure reaches 0.1 MPaG. This operation is repeated a total of 5 times.

[0123] Next, a cleaning process is performed on the high-pressure gas container. Specifically, with the container valve open, 500 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm (volume) is added to the high-pressure gas container (hydrogen halide supply stage). Then, the container is left to stand for 24 hours while maintaining a temperature between 15°C and 25°C (metal oxide removal stage). Afterward, the container valve is closed, and the gas is then... Figure 1 Remove from the device shown, and discharge hydrogen chloride from the high-pressure gas container via the liquid-phase siphon until the residual pressure becomes 0.11 MPa (discharge stage). Repeat the cleaning process described above a total of 3 times.

[0124] After the cleaning process, 500 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm by volume was refilled into the high-pressure gas container. Then, the moisture concentration and hydrogen molecule concentration of the hydrogen chloride filled into the high-pressure gas container were measured in the same manner as in Example 1. As a result, the moisture concentration of the hydrogen chloride was 0.8 ppm by volume, and the hydrogen molecule concentration of the hydrogen chloride was less than 0.1 ppm by volume. The results are shown in Table 1.

[0125] [Example 4]

[0126] The hydrogen halide used in the cleaning process was changed from hydrogen chloride with a moisture concentration of less than 0.2 ppm by volume to hydrogen bromide with a moisture concentration of less than 0.2 ppm by volume, and the amount of hydrogen bromide supplied during the hydrogen halide supply stage was 20 kg. Otherwise, the cleaning of the high-pressure gas container was carried out in the same manner as in Example 1.

[0127] After the cleaning process, 20 kg of hydrogen bromide with a moisture concentration of less than 0.2 ppm by volume was refilled into the high-pressure gas container. Then, the moisture concentration and hydrogen molecule concentration of the hydrogen bromide filled into the high-pressure gas container were measured in the same manner as in Example 1. The results showed that the moisture concentration of the hydrogen bromide was 0.9 ppm by volume and the hydrogen molecule concentration of the hydrogen bromide was less than 0.1 ppm by volume. The results are shown in Table 1.

[0128] [Example 5]

[0129] The cleaning process is performed once, and the temperature of the metal oxide removal stage is changed to above 35°C and below 40°C. Otherwise, the high-pressure gas container is cleaned in the same way as in Example 1.

[0130] After the cleaning process, 25 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm by volume was refilled into the high-pressure gas container. Then, the moisture concentration and hydrogen molecule concentration of the hydrogen chloride filled into the high-pressure gas container were measured in the same manner as in Example 1. The results showed that the moisture concentration of the hydrogen chloride was 0.3 ppm by volume and the hydrogen molecule concentration was 12 ppm by volume. The results are shown in Table 1.

[0131] [Example 6]

[0132] The maximum height Rz of the inner surface of the main body of the high-pressure gas container was set to 5 μm, and the high-pressure gas container was cleaned in the same manner as in Example 1.

[0133] After the cleaning process, 25 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm by volume was refilled into the high-pressure gas container. Then, the moisture concentration and hydrogen molecule concentration of the hydrogen chloride filled into the high-pressure gas container were measured in the same manner as in Example 1. As a result, the moisture concentration of the hydrogen chloride was 0.7 ppm by volume, and the hydrogen molecule concentration of the hydrogen chloride was less than 0.1 ppm by volume. The results are shown in Table 1.

[0134] [Example 7]

[0135] The temperature during the decompression stage was changed to above 45°C and below 50°C. Otherwise, the high-pressure gas container was cleaned in the same manner as in Example 1.

[0136] After the cleaning process, 25 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm by volume was refilled into the high-pressure gas container. Then, the moisture concentration and hydrogen molecule concentration of the hydrogen chloride filled into the high-pressure gas container were measured in the same manner as in Example 1. As a result, the moisture concentration of the hydrogen chloride was 0.3 ppm by volume, and the hydrogen molecule concentration of the hydrogen chloride was less than 0.1 ppm by volume. The results are shown in Table 1.

[0137] [Example 8]

[0138] During the decompression phase, the pressure is reduced until the internal pressure of the high-pressure gas container reaches 5 Pa. Otherwise, the high-pressure gas container is cleaned in the same manner as in Example 1.

[0139] After the cleaning process, 25 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm by volume was refilled into the high-pressure gas container. Then, the moisture concentration and hydrogen molecule concentration of the hydrogen chloride filled into the high-pressure gas container were measured in the same manner as in Example 1. The results showed that the moisture concentration of the hydrogen chloride was 0.8 ppm by volume and the hydrogen molecule concentration was less than 0.1 ppm by volume. The results are shown in Table 1.

[0140] [Example 9]

[0141] During the inactive gas supply phase, nitrogen is filled into the high-pressure gas container until the internal pressure becomes 0.1 MPa. Otherwise, the high-pressure gas container is cleaned in the same manner as in Example 1.

[0142] After the cleaning process, 25 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm by volume was refilled into the high-pressure gas container. Then, the moisture concentration and hydrogen molecule concentration of the hydrogen chloride filled into the high-pressure gas container were measured in the same manner as in Example 1. The results showed that the moisture concentration of the hydrogen chloride was 0.9 ppm by volume and the hydrogen molecule concentration was less than 0.1 ppm by volume. The results are shown in Table 1.

[0143] [Example 10]

[0144] The maximum height Rz of the inner surface of the main body of the high-pressure gas container was set to 20 μm, and the cleaning process was performed 5 times. Otherwise, the high-pressure gas container was cleaned in the same way as in Example 1.

[0145] After the cleaning process, 25 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm by volume was refilled into the high-pressure gas container. Then, the moisture concentration and hydrogen molecule concentration of the hydrogen chloride filled into the high-pressure gas container were measured in the same manner as in Example 1. The results showed that the moisture concentration of the hydrogen chloride was 1.2 ppm by volume and the hydrogen molecule concentration was less than 0.1 ppm by volume. The results are shown in Table 1.

[0146] [Example 11]

[0147] During the decompression phase, the pressure is reduced until the internal pressure of the high-pressure gas container reaches 10 Pa. Otherwise, the high-pressure gas container is cleaned in the same manner as in Example 1.

[0148] After the cleaning process, 25 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm by volume was refilled into the high-pressure gas container. Then, the moisture concentration and hydrogen molecule concentration of the hydrogen chloride filled into the high-pressure gas container were measured in the same manner as in Example 1. The results showed that the moisture concentration of the hydrogen chloride was 1.5 ppm by volume and the hydrogen molecule concentration was less than 0.1 ppm by volume. The results are shown in Table 1.

[0149] [Example 12]

[0150] During the inactive gas supply phase, nitrogen is filled into the high-pressure gas container until the internal pressure reaches 0.05 MPa. Otherwise, the high-pressure gas container is cleaned in the same manner as in Example 1.

[0151] After the cleaning process, 25 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm by volume was refilled into the high-pressure gas container. Then, the moisture concentration and hydrogen molecule concentration of the hydrogen chloride filled into the high-pressure gas container were measured in the same manner as in Example 1. The results showed that the moisture concentration of the hydrogen chloride was 1.1 ppm by volume and the hydrogen molecule concentration of the hydrogen chloride was less than 0.1 ppm by volume. The results are shown in Table 1.

[0152] [Example 13]

[0153] The pressure accumulator purification process is performed once, and the high-pressure gas container is cleaned in the same manner as in Example 1.

[0154] After the cleaning process, 25 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm by volume was refilled into the high-pressure gas container. Then, the moisture concentration and hydrogen molecule concentration of the hydrogen chloride filled into the high-pressure gas container were measured in the same manner as in Example 1. The results showed that the moisture concentration of the hydrogen chloride was 1.3 ppm by volume and the hydrogen molecule concentration was less than 0.1 ppm by volume. The results are shown in Table 1.

[0155] [Example 14]

[0156] The amount of hydrogen chloride supplied during the hydrogen halide supply stage was set to 2 kg, and the cleaning process was performed 20 times. Otherwise, the high-pressure gas container was cleaned in the same manner as in Example 1.

[0157] After the cleaning process, 25 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm by volume was refilled into the high-pressure gas container. Then, the moisture concentration and hydrogen molecule concentration of the hydrogen chloride filled into the high-pressure gas container were measured in the same manner as in Example 1. The results showed that the moisture concentration of the hydrogen chloride was 1.5 ppm by volume and the hydrogen molecule concentration was less than 0.1 ppm by volume. The results are shown in Table 1.

[0158] [Example 15]

[0159] Prepare a modular body consisting of 10 metal high-pressure gas containers with a volume of 1100L, connected in parallel by two sets of manifolds (see reference). Figure 5 The inner surface of the high-pressure gas container is ground, with a maximum height Rz of 1 μm on the inner surface of the main body and a maximum height Rz of 20 μm on the inner surface of the parts other than the main body. No coating material is applied to the inner surface of the high-pressure gas container.

[0160] Install the module body Figure 2 The apparatus shown incorporates a pressure-accumulating purification process. Specifically, it involves a decompression phase where the temperature is maintained between 15°C and 25°C until the internal pressure of the high-pressure gas container and manifold reaches 3 Pa. Following this, a non-reactive gas supply phase involves filling the high-pressure gas container and manifold with nitrogen gas containing less than 0.05 ppm by volume until the internal pressure reaches 0.3 MPa. The decompression and non-reactive gas supply phases are alternately repeated three times each. The moisture concentration of the nitrogen gas filling the high-pressure gas container is determined using an optical cavity ring-down spectroscopy analyzer, and the result is less than 0.1 ppm by volume.

[0161] Next, the module body after the pressure-accumulation purification process is depressurized under the same conditions as the depressurization stage of the pressure-accumulation purification process, and then... Figure 2 Remove the module from the device shown and install it. Figure 1 On the device shown. Then, set all the valves of the 10 high-pressure gas containers to the closed state, and... Figure 1 Hydrogen chloride is supplied to the manifold of the device and module shown until the pressure reaches 1.80 MPaG, then depressurized until the residual pressure reaches 0.1 MPaG. This operation is repeated a total of 15 times.

[0162] Next, a cleaning process is performed on the module body. Specifically, the valves of the high-pressure gas containers are opened, and 660 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm (by volume) is added to each high-pressure gas container via one of the manifolds (a total of 6600 kg of hydrogen chloride is added) (hydrogen halide supply stage). Subsequently, hydrogen chloride remains in both gaseous and liquid phases within one of the manifolds, and hydrogen chloride is also supplied from one high-pressure gas container to the other manifold until the concentration reaches 3 MPaG.

[0163] Subsequently, the module was left to stand for 24 hours while maintaining a temperature between 15°C and 25°C (metal oxide removal stage). Next, the valve of the high-pressure gas container was closed, and... Figure 1 The module body is removed from the device shown, and hydrogen chloride is discharged one by one from each high-pressure gas container through the liquid phase side siphon until the residual pressure becomes 0.11 MPa (discharge stage). The cleaning process described above is repeated a total of 2 times.

[0164] After each cleaning process, 660 kg of hydrogen chloride (totaling 6600 kg) was refilled into the high-pressure gas container with a moisture concentration of less than 0.2 ppm by volume. The moisture concentration of the hydrogen chloride in the high-pressure gas container was then determined using a cavity ring-down spectroscopy analyzer, and the hydrogen molecule concentration was determined by gas chromatography. A pulsed discharge photoionization detector was used as the detector in the gas chromatography. The results showed that the moisture concentration of the hydrogen chloride was 0.3 ppm by volume, and the hydrogen molecule concentration was less than 0.1 ppm by volume. The results are shown in Table 1.

[0165] [Example 16]

[0166] The two manifolds were left empty, and the module was filled with 660 kg of hydrogen chloride in each of the 10 high-pressure gas containers. The cleaning process was repeated a total of 3 times. Otherwise, the module was cleaned in the same way as in Example 15.

[0167] After each cleaning process, 660 kg of hydrogen chloride (totaling 6600 kg) was refilled into the high-pressure gas container with a moisture concentration of less than 0.2 ppm by volume. The moisture concentration of the hydrogen chloride in the high-pressure gas container was then determined using a cavity ring-down spectroscopy analyzer, and the hydrogen molecule concentration was determined by gas chromatography. A pulsed discharge photoionization detector was used as the detector in the gas chromatography. The results showed that the moisture concentration of the hydrogen chloride was 0.6 ppm by volume, and the hydrogen molecule concentration was less than 0.1 ppm by volume. The results are shown in Table 1.

[0168] [Comparative Example 1]

[0169] No pressure accumulator purification process was performed; otherwise, the high-pressure gas container was cleaned in the same manner as in Example 1.

[0170] After the cleaning process, 25 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm by volume was refilled into the high-pressure gas container. Then, the moisture concentration and hydrogen molecule concentration of the hydrogen chloride filled into the high-pressure gas container were measured in the same manner as in Example 1. The results showed that the moisture concentration of the hydrogen chloride was 2.0 ppm by volume and the hydrogen molecule concentration was less than 0.1 ppm by volume. The results are shown in Table 1.

[0171]

[0172] Explanation of reference numerals in the attached figures

[0173] 1. Purification helium cylinder

[0174] 2··· Pressure reducing valve

[0175] 3, 4, 6, 8, 11... valves

[0176] 5. Hydrogen halide supply source

[0177] 7···47L High-Pressure Gas Container

[0178] 9. Pressure gauge

[0179] 10. Check valve

[0180] 12··· Discharge Unit

[0181] 13. Nitrogen supply source

[0182] Valves 14, 15, 16...

[0183] 17. Vacuum Pump

[0184] 18. Vacuum gauge

[0185] 19···47L High-Pressure Gas Container

[0186] 20···Gas-side container valve

[0187] 21···Gas-phase side siphon

[0188] 22···Liquid-side siphon tube

[0189] 23···Liquid phase side container valve

[0190] 24···440L High-Pressure Gas Container

[0191] 25···Gas-side container valve

[0192] 26···Liquid phase side container valve

[0193] Safety bolts 27, 30...

[0194] 28···Gas-phase side siphon

[0195] 29···Liquid-side siphon tube

[0196] 31, 33... skirt

[0197] 32···900L High-Pressure Gas Container

[0198] 34···1100L High-Pressure Gas Container

[0199] 35···Container Valve

[0200] 36···Module body framework

[0201] 37··· Manifold piping

[0202] 38··· Pressure gauge

[0203] 39. Manifold terminal valve

Claims

1. A method for cleaning a high-pressure gas container, comprising: a pressure-accumulating purification step for purifying the interior of the high-pressure gas container, and a cleaning step for cleaning the interior of the high-pressure gas container after the pressure-accumulating purification step. The pressure-accumulation purification process includes: The decompression stage, which brings the interior of the high-pressure gas container into a decompression state, and The inactive gas supply stage involves supplying inactive gas to the high-pressure gas container. The cleaning process includes a hydrogen halide supply stage, a metal oxide removal stage, and a discharge stage. The hydrogen halide supply stage is the process of supplying hydrogen halide to the high-pressure gas container after the pressure storage and purification process. The metal oxide removal stage is a process performed inside the high-pressure gas container after the hydrogen halide supply stage, whereby the metal oxides present on the inner surface of the high-pressure gas container react with the hydrogen halide supplied during the hydrogen halide supply stage to generate water. The discharge stage is the process of discharging the water generated in the metal oxide removal stage and the hydrogen halide supplied through the hydrogen halide supply stage from the high-pressure gas container.

2. The cleaning method for a high-pressure gas container according to claim 1, wherein no coating material is applied to the inner surface of the high-pressure gas container, and the maximum height Rz of the inner surface of the main body of the high-pressure gas container is less than 5 μm.

3. The cleaning method for a high-pressure gas container according to claim 1 or 2, wherein the decompression stage of the pressure accumulating and purification process is a process of venting the high-pressure gas container while maintaining it at a temperature below 50°C until the internal pressure becomes below 5Pa, and the inactive gas supply stage of the pressure accumulating and purification process is a process of supplying the high-pressure gas container with an inactive gas having a moisture concentration of less than 0.1 ppm by volume until the internal pressure becomes above 0.1 MPa.

4. The cleaning method for the high-pressure gas container according to claim 1 or 2, wherein the pressure accumulating and purification process is repeated more than twice.

5. The cleaning method for a high-pressure gas container according to claim 1 or 2, wherein the hydrogen halide is at least one selected from hydrogen fluoride, hydrogen chloride, hydrogen bromide, and hydrogen iodide.

6. The cleaning method for a high-pressure gas container according to claim 1 or 2, wherein the hydrogen halide supply stage is a process of supplying hydrogen halide to the high-pressure gas container until the hydrogen halide is liquefied within the high-pressure gas container.

7. The cleaning method for a high-pressure gas container according to claim 1 or 2, wherein the metal oxide removal stage is a process of letting the high-pressure gas container, after being supplied with hydrogen halide through the hydrogen halide supply stage, stand at a temperature below 30°C for more than one day.

8. The cleaning method for a high-pressure gas container according to claim 1 or 2, wherein when the volume of the high-pressure gas container is 10L or more and 50L or less, the discharge stage is a process of discharging the water and the hydrogen halide from the high-pressure gas container by inverting the high-pressure gas container.

9. The cleaning method for a high-pressure gas container according to claim 1 or 2, wherein when the volume of the high-pressure gas container exceeds 50L and is less than 1000L, the discharge stage is a process of inserting an inner tube into the interior of the high-pressure gas container and using the inner tube to discharge the liquid phase water and the hydrogen halide from the high-pressure gas container.

10. The cleaning method for a high-pressure gas container according to claim 1 or 2, wherein the volume of the high-pressure gas container exceeds 1000L and is less than 1500L, and two or more of the high-pressure gas containers are connected in parallel by a manifold to form a module, the discharge stage is a process of inserting an inner tube into the interior of the two or more high-pressure gas containers respectively, and using the inner tube to discharge the liquid phase water and the hydrogen halide from the two or more high-pressure gas containers respectively through the manifold.

11. The cleaning method for high-pressure gas containers according to claim 10, wherein the manifold is connected only to one side of the two or more high-pressure gas containers, or is connected to both sides respectively.

12. The cleaning method for a high-pressure gas container according to claim 1 or 2, wherein the cleaning process is repeated more than twice after the pressure accumulating and purification process.

13. The cleaning method for a high-pressure gas container according to claim 1 or 2, wherein the metal oxide is at least one selected from iron oxide, chromium oxide, molybdenum oxide, and manganese oxide.

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