JP2016109171A - High-pressure gas container cleaning method and high-pressure gas container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning method suitable for removing a water content in a high-pressure gas container.SOLUTION: A high-pressure gas container cleaning method includes: a pressure rise step of introducing a gas having hydrophilic property into the high-pressure gas container to raise the pressure; and a gas discharging step of discharging the gas in the high-pressure gas container, where the steps are conducted repeatedly.SELECTED DRAWING: None

Description

  The present invention relates to a cleaning method for removing moisture in a high-pressure gas container.

  Many high-pressure gas containers are used to carry standard gas for calibration of medical equipment and analytical equipment and high-purity gas for semiconductors. In order to maintain the quality of these standard gas and high-purity gas for a long period of time, a cleaning process in an appropriate container is performed before filling the gas. In particular, in a gas container having a strong affinity with water such as hydrogen chloride, chlorine, sulfur dioxide, and ammonia, it is necessary to sufficiently remove the water in the container before filling.

  As a method for removing moisture in a metal high-pressure gas container containing iron, chromium, molybdenum, manganese, and alloys thereof, generally, (1) cleaning with repeated pressurization and depressurization using an inert gas such as nitrogen (2) Warm vacuum cleaning in which the container is heated and the pressure is increased and reduced using an inert gas such as nitrogen. However, in these methods, after moisture removal with an inert gas, moisture cannot be removed sufficiently, and if a hydrophilic gas (gas having an affinity for moisture) is filled, There is a problem that the quality of stable standard gas and high-purity gas cannot be obtained, for example, the moisture and gas remaining in a minute amount are compatible with each other and the gas purity is lower than the concentration at the time of preparation. Further, depending on the type of gas, the inner surface of the high-pressure gas container may rust and corrode.

  For example, Patent Documents 1 and 2 listed below relate to cleaning for removing moisture in a container or the like. In Patent Document 1, liquefied hydrogen chloride is filled in a container and heated at 30 to 50 ° C. to remove moisture and oxides that cause moisture in the high-pressure gas container. However, since it is filled with liquefied hydrogen chloride and then discharged, a large amount of product (liquefied hydrogen chloride) is used, which is not an economical method.

  In Patent Document 2, high purity hydrogen chloride, high purity hydrogen bromide, and high purity ammonia are used to remove moisture on the substrate. However, since only gas is sprayed on the substrate, the water removal efficiency is poor, and a large amount of cleaning gas is required. In addition, since a general high-pressure gas container has a single gas inlet, the gas flow is uneven, and only a part of the container can be sprayed with high-purity gas, and moisture is removed to every corner of the container. It is difficult.

Japanese Patent No. 3920544 JP-A-9-106974

  The present invention has been conceived under such circumstances, and it is an object of the present invention to provide a cleaning method suitable for removing moisture in a high-pressure gas container.

  The method for cleaning a high-pressure gas container provided by the first aspect of the present invention includes a pressure-increasing step for introducing a hydrophilic gas into the high-pressure gas container and increasing the pressure, and an exhausting step for exhausting the gas in the high-pressure gas container. And repeating the above.

  Preferably, the maximum pressure inside the high-pressure gas container in the pressurizing step is 0.1 MPaG or more.

  Preferably, the minimum pressure inside the high-pressure gas container in the exhaust process is not more than atmospheric pressure.

  Preferably, the high-pressure gas container has a fusible plug that melts at a predetermined operating temperature or higher, and the temperature of the high-pressure gas container is 30 ° C. or higher and lower than the operating temperature in the pressurizing step and the exhausting step. Maintained.

  Preferably, the purity of the gas having hydrophilicity introduced into the high-pressure gas container is 99.99 vol. % Or more.

  Preferably, the gas having hydrophilicity is any one gas selected from the group consisting of hydrogen chloride, hydrogen bromide, chlorine, sulfur dioxide, and ammonia.

  The high-pressure gas container provided by the second aspect of the present invention is characterized by performing a cleaning process by the high-pressure gas container cleaning method according to the first aspect of the present invention.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

The schematic structure of the washing | cleaning apparatus which can be used for performing the washing | cleaning method of the high pressure gas container which concerns on this invention is represented.

  Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.

  FIG. 1 shows a schematic configuration of a cleaning apparatus X that can be used to execute the cleaning method for a high-pressure gas container according to the present invention. The cleaning device X of the present embodiment includes a high-pressure gas container 1, a hydrogen chloride gas supply source 2, a liquefied hydrogen chloride supply source 3, a pipe 4 connecting them, and an on-off valve 51 provided at an appropriate position of the pipe 4. 52, 53, and 54, and is configured so that the inside of the container can be cleaned by introducing hydrogen chloride as a hydrophilic gas into the high-pressure gas container 1.

  The high-pressure gas container 1 is used for, for example, filling high purity liquefied gas as a product. The high-pressure gas container 1 includes a container main body 11 and a container valve 12 connected to the container main body 11.

  The container body 11 is a pressure-resistant container having a predetermined capacity, and is made of metal including, for example, iron and an iron alloy. The container valve 12 includes a handle 121, a connection part 122, and a fusible plug 123. The handle 121 switches the opening and closing of the flow path between the container main body 11 and the connection portion 122 by operating the handle 121. The connection part 122 is a joint part that bears connection with the pipe 4. In a state where the container valve 12 is closed, the high-pressure gas container 1 can be attached to and detached from the pipe 4 (a partial pipe 41 described later) while maintaining a sealed state. Prior to filling the high-pressure gas container 1 with the product, the inside of the high-pressure gas container 1 is cleaned with a cleaning gas. A heating means (not shown) for keeping the high-pressure gas container 1 at a predetermined temperature at the time of cleaning is provided on the outer peripheral portion of the high-pressure gas container 1.

  In the present embodiment, the case where hydrogen chloride and its liquefied gas are used as the cleaning gas for the high-pressure gas container 1 and the product filled in the high-pressure gas container 1 will be described as an example. It is not limited to. As the cleaning gas and the product (liquefied gas), a hydrophilic gas (a gas having a strong affinity with water) is used. Examples of such hydrophilic gas include hydrogen bromide, chlorine, sulfur dioxide, and ammonia.

  The fusible plug 123 is configured to be capable of releasing the gas inside the container body 11 to the outside by melting and opening when the temperature becomes equal to or higher than a predetermined operating temperature. For example, the fusible plug 123 includes a fusible metal that melts at an operating temperature or higher, and functions as a safety valve that prevents the inside of the high-pressure gas container 1 from becoming an excessively high pressure state. The operating temperature of the fusible plug 123 varies depending on the type of liquefied gas filled in the high-pressure gas container 1. For example, the operating temperature of the fusible plug 123 is 70 ° C. when the liquefied gas to be filled is liquefied hydrogen chloride or liquefied hydrogen bromide, 61 ° C. when it is liquefied chlorine, and 58 ° C. when it is liquefied sulfur dioxide. In the case of liquefied ammonia, the temperature is 57 ° C.

  The hydrogen chloride gas supply source 2 stores high-purity hydrogen chloride gas as a cleaning gas. The purity of the hydrogen chloride gas (cleaning gas) is, for example, 99.99 vol. % Or more, preferably 99.999 vol. % Or more.

  The liquefied hydrogen chloride supply source 3 stores liquefied hydrogen chloride as a product.

  The pipe 4 has partial pipe lines 41 to 46. The partial pipeline 41 is connected to the high-pressure gas container 1, and the partial pipeline 42 is connected to the hydrogen chloride gas supply source 2. The partial conduit 42 is provided with a flow rate regulator 61 and an on-off valve 51. The flow rate regulator 61 controls the cleaning gas supplied from the liquefied hydrogen gas supply source 2 to a predetermined flow rate.

  The partial pipeline 44 connects the partial pipeline 41 and the partial pipeline 42, and the partial pipelines 42, 44, 41 form a flow path from the hydrogen chloride gas supply source 2 to the high-pressure gas container 1. A pressure gauge 62 is connected to the partial conduit 44.

  The partial pipe 43 is connected to the liquefied hydrogen chloride supply source 3 and extends in a branched manner with respect to the partial pipe 42 (44). An open / close valve 52 is provided in the partial pipeline 43. The partial pipes 43, 44, 41 form a flow path from the liquefied hydrogen chloride supply source 3 to the high pressure gas container 1.

  The partial pipeline 45 extends in a branched manner with respect to the partial pipeline 41 (44). The partial pipe 45 is provided with an on-off valve 53 and a pressure reducing valve 63. The analyzer 7 is connected to the end of the partial conduit 45. The partial pipeline 46 extends in a branched manner with respect to the partial pipeline 44. The partial conduit 46 is provided with an on-off valve 54 and a pump 64.

  When cleaning the high-pressure gas container 1 using the cleaning device X having the above-described configuration, hydrogen chloride gas is introduced into the high-pressure gas container 1 to increase the pressure (pressure-increasing step), and the gas in the high-pressure gas container 1 is subsequently exhausted. (Exhaust process), and the pressure increasing process and the exhaust process are repeated.

  In the boosting step, the on-off valve 51 is opened and the on-off valves 52, 53, 54 are closed, and the gas derived from the hydrogen chloride gas supply source 2 is supplied to the partial pipe 42, the flow rate regulator 61, the on-off valve. 51 and partial pipes 44 and 41 are introduced into the high-pressure gas container 1. The maximum pressure inside the high-pressure gas container 1 in the pressurization process may be, for example, 0.0 MPaG (gauge pressure) or more when the minimum pressure in the subsequent exhaust process is less than atmospheric pressure, and the minimum pressure in the exhaust process is In the case of about atmospheric pressure, for example, the pressure is set to 0.1 MPaG (gauge pressure) or more, preferably 0.3 MPaG or more.

  In the exhaust process, the on-off valve 54 is opened and the on-off valves 51, 52, 53 are closed, and the gas in the high-pressure gas container 1 is discharged. The gas discharged from the high-pressure gas container 1 is discharged out of the system through the partial pipelines 41, 44, 46, the on-off valve 54, and the pump 64. The minimum pressure inside the high-pressure gas container 1 in the exhaust process is, for example, not more than atmospheric pressure, and is preferably not more than -0.05 MPaG (gauge pressure). When the internal pressure of the high-pressure gas container 1 in the exhaust process is set to about atmospheric pressure, the pump 64 is not necessary.

  When cleaning the high-pressure gas container 1 (that is, when repeating the pressurization process and the exhaust process), the high-pressure gas container 1 is heated to a predetermined temperature. The temperature of the high-pressure gas container 1 at the time of cleaning is maintained at, for example, 30 ° C. or higher and lower than the operating temperature of the fusible plug 123.

  The number of times of repeating the pressurization process and the exhaust process when cleaning the high-pressure gas container 1 is not particularly limited, but is, for example, 10 times or more. Further, in the pressurization process, hydrogen chloride gas (cleaning gas) may be exhausted immediately after being introduced into the high-pressure gas container 1 or may be exhausted after being allowed to stand for a predetermined time in the pressurization state after the introduction of the gas. Good. When it is allowed to stand in a pressure-increasing state, the standing time is preferably set to 1 hour or longer, for example.

  The gas discharged from the high-pressure gas container 1 is appropriately sent to the analyzer 7, and the moisture concentration in the gas is measured.

  When the cleaning of the high pressure gas container 1 is completed, the high pressure gas container 1 is filled with a product (liquefied hydrogen chloride). The product may be filled by using a compression pump, or by using the differential pressure due to the vapor pressure by keeping the temperature of the high-pressure gas container 1 lower than the temperature of the liquefied hydrogen chloride supply source 3. Also good. At the time of filling, the on-off valve 52 is opened and the on-off valves 51, 53, 54 are closed, and liquefied hydrogen chloride is led out from the liquefied hydrogen chloride supply source 3. The liquefied hydrogen chloride derived from the liquefied hydrogen chloride supply source 3 is introduced into the high-pressure gas container 1 through the partial pipe 43, the on-off valve 52, and the partial pipes 44 and 41.

  According to the method for cleaning the high-pressure gas container 1 of the present embodiment, the introduction of the hydrogen chloride gas (cleaning gas) to the high-pressure gas container 1 (pressure increase process) and the discharge (exhaust process) are repeated. Cleaning can be performed. The water concentration of the gas discharged from the high-pressure gas container 1 after cleaning is 10 vol. It has fallen to about ppm or less. By increasing the number of repetitions of pressurization and exhaust, the water content in the exhaust gas after cleaning is 1 vol. It can be reduced to ppm or less. Thus, according to this cleaning method, the water in the high-pressure gas container 1 is sufficiently removed.

  As described above, the reason why the cleaning efficiency is increased by repeatedly introducing and exhausting the cleaning gas into the high-pressure gas container 1 has not yet been elucidated, but the surface within the container (rough surface having fine irregularities) It is presumed that the moisture adsorbed on () appears on the surface due to the change in pressure and becomes more compatible with the newly introduced corrosive gas (hydrophilic gas). It is also presumed that water-affinity gas reaches every corner of the container by repeating the introduction and exhaust of the cleaning gas, thereby improving the cleaning efficiency.

  In the present embodiment, the product (liquefied gas) filled in the high-pressure gas container 1 after cleaning and the cleaning gas used for the cleaning process are the same gas type. For this reason, compared with the case of cleaning with an inert gas such as nitrogen, there is no need for a post-cleaning treatment such as replacing the gas in the container with the product gas immediately before the product is finally filled, The trouble of the post-cleaning process can be saved.

  According to the configuration including the liquefied hydrogen chloride supply source 3 as in the present embodiment, it is possible to continuously fill the product (liquefied hydrogen chloride) after the high-pressure gas container 1 is cleaned. However, the liquefied hydrogen chloride supply source 3 is not necessarily provided. When the liquefied hydrogen chloride supply source 3 is not provided, the high pressure gas container 1 may be removed from the pipe 4 after being cleaned with the cleaning gas, and the high pressure gas container 1 may be separately filled with liquefied hydrogen chloride.

  While specific embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention. The specific configuration of the high pressure gas container cleaning method and the cleaning apparatus for executing the cleaning method according to the present invention may be different from the above embodiment.

  When operating the high-pressure gas container cleaning method according to the present invention in equipment for producing high-purity product gas, instead of discarding the gas discharged from the high-pressure gas container after cleaning, for example, it is vented to a buffer tank, etc. It can be reused through dehydrating agents and filters.

  Next, the usefulness of the present invention will be described with reference to comparative examples and examples. The cleaning treatments in the following comparative examples and examples were all performed using a metal high-pressure gas container (internal capacity 47 L) equipped with a container valve (soluble plug operating temperature 70 ° C.).

[Comparative Example 1]
Maintaining the high-pressure gas container at 65 ° C., as a pretreatment, nitrogen (purity 99.999 vol.%) Was introduced, the pressure was increased to 0.1 MPaG, and vacuum nitrogen replacement was performed to evacuate to 0.1 kPa (absolute pressure). 4 times. Then, after introducing high-purity hydrogen chloride gas (purity 99.999 vol.%) To 0.4 MPaG and bringing it to room temperature (25 ° C.), the water concentration in the hydrogen chloride gas taken out from the container was measured to be 30 vol. ppm. Further, after the pretreatment, vacuum nitrogen replacement under the same pressure and pressure reduction conditions as in the pretreatment was performed 30 times, and then high purity hydrogen chloride gas (purity 99.999 vol.%) Was introduced to 0.4 MPaG to room temperature. (25 ° C.) After measuring the water concentration in the hydrogen chloride gas taken out from the container, 29 vol. ppm. From this result, it can be said that the water in the high-pressure gas container cannot be sufficiently removed by heating and decompression replacement with nitrogen.

[Example 1]
After performing the same pretreatment as in Comparative Example 1 (vacuum nitrogen replacement four times), the high-pressure gas container was kept at 50 ° C., and high-purity hydrogen chloride gas (purity 99.999 vol.%) Was introduced. Hydrogen chloride gas vacuum replacement was performed 30 times by increasing the pressure to 15 MPaG and evacuating the pressure to 10 kPa. Thereafter, when high purity hydrogen chloride gas was introduced to 0.4 MPaG and the water concentration in the hydrogen chloride gas taken out from the container was measured at room temperature (25 ° C.), 1.0 vol. It was below ppm. In addition, the water concentration in hydrogen chloride at the time of hydrogen chloride gas vacuum substitution 5th time is 20 vol. ppm. Similarly, the water concentration in hydrogen chloride at the 15th time was 4 vol. ppm. The high-purity hydrogen chloride used for washing was about 3600 L (standard condition conversion). As a reference, the amount of liquefied hydrogen chloride that can be safely filled when cleaning with a 47 L container filled with liquefied hydrogen chloride is approximately 25 kg (approximately 15500 L in terms of gas in the standard state). It can be seen that the use of cleaning gas requires far less amount of cleaning gas.

[Example 2]
After performing the same pretreatment as in Comparative Example 1 (vacuum nitrogen replacement four times), the high-pressure gas container was kept at 50 ° C., and high-purity hydrogen chloride gas (purity 99.999 vol.%) Was introduced. The pressure was increased to 15 MPaG, and hydrogen chloride gas vacuum substitution was performed 10 times to evacuate the pressure to 10 kPa (absolute pressure). Thereafter, high purity hydrogen chloride gas was introduced, the pressure was increased to 0.3 MPaG, and the mixture was allowed to stand for 65 hours. Then, after evacuating to 10 kPa (absolute pressure), high-purity hydrogen chloride gas was introduced, the pressure was increased to 0.15 MPaG, and hydrogen chloride gas vacuum substitution was performed 15 times to evacuate at a reduced pressure of 10 kPa (absolute pressure). . Thereafter, when high purity hydrogen chloride gas was introduced to 0.4 MPaG and the water concentration in the hydrogen chloride gas taken out from the container was measured at room temperature (25 ° C.), 1.0 vol. It was below ppm. In the analysis immediately after standing for 65 hours, the water concentration was 20 vol. The water concentration was higher than that of the fifteenth hydrogen chloride vacuum replacement in Example 1, and a cleaning effect was observed by leaving it in a pressurized state. The high-purity hydrogen chloride used for washing was about 3000 L (converted to the standard state).

Example 3
After performing the same pretreatment as in Comparative Example 1 (vacuum nitrogen replacement four times), the high-pressure gas container was kept at 50 ° C., and high-purity hydrogen chloride gas (purity 99.999 vol.%) Was introduced. Replacement was performed 50 times by increasing the pressure to 50 MPaG and exhausting to 0.05 MPaG (about atmospheric pressure). Thereafter, when high purity hydrogen chloride gas was introduced to 0.5 MPaG and the water concentration in the hydrogen chloride gas taken out from the container was measured at room temperature (25 ° C.), 5 vol. ppm. The high-purity hydrogen chloride used for washing was about 12000 L (converted to standard conditions).

Example 4
After performing the same pretreatment as in Comparative Example 1 (vacuum nitrogen replacement four times), the high-pressure gas container was kept at 50 ° C., and high-purity hydrogen chloride gas (purity 99.999 vol.%) Was introduced. Hydrogen chloride gas vacuum replacement was performed once by increasing the pressure to 0 MPaG and evacuating the pressure to 10 kPa (absolute pressure). Thereafter, high-purity hydrogen chloride gas was introduced, the pressure was increased to 0.4 MPaG, and the mixture was allowed to stand for 24 hours. Then, after evacuating to 10 kPa (absolute pressure), high-purity hydrogen chloride gas was introduced, the pressure was increased to 0.4 MPaG, and hydrogen chloride gas vacuum substitution was performed once to evacuate at a reduced pressure of 10 kPa (absolute pressure). . Thereafter, when high purity hydrogen chloride gas was introduced to 0.4 MPaG and the water concentration in the hydrogen chloride gas taken out from the container was measured at room temperature (25 ° C.), 2.0 vol. ppm. In the analysis immediately after standing for 24 hours, the water concentration was 40 vol. ppm. From this, it is thought that the water | moisture content in a container was able to fully spring out by heating and leaving still for 24 hours. High-purity hydrogen chloride used for washing was about 600 L (converted to standard conditions).

Example 5
After the same pretreatment as in Comparative Example 1 (vacuum nitrogen replacement four times), the high-pressure gas container was kept at 45 ° C., and high-purity ammonia gas (purity 99.999 vol.%) Was introduced, and 0.10 MPaG The pressure was increased to 1, and the ammonia gas vacuum substitution was performed 20 times to evacuate the pressure to 0.1 kPa (absolute pressure). Then, after introducing high-purity ammonia gas to 0.4 MPaG and bringing it to room temperature (25 ° C.), when the water concentration in the ammonia gas taken out from the container is measured at room temperature, 1.0 vol. It was below ppm. The high-purity ammonia used for washing was about 2000 L (converted to the standard state).

Example 6
After performing the same pretreatment as in Comparative Example 1 (vacuum nitrogen replacement four times), the high-pressure gas container was kept at 50 ° C., and high-purity hydrogen chloride gas (purity 99.999 vol.%) Was introduced. Hydrogen chloride gas vacuum replacement was performed 30 times by increasing the pressure to 15 MPaG and evacuating the pressure to 10 kPa. Thereafter, when high purity hydrogen chloride gas was introduced to 0.4 MPaG and the water concentration in the hydrogen chloride gas taken out from the container was measured at room temperature (25 ° C.), 1.0 vol. It was below ppm. Thereafter, high-purity hydrogen chloride gas was introduced, the pressure was increased to 0.3 MPaG, the mixture was allowed to stand for 65 hours, and then the water concentration in the hydrogen chloride gas taken out from the container was measured at room temperature (25 ° C.). It was below ppm. There was no change in the water concentration in the hydrogen chloride gas taken out from the container before being allowed to stand in a pressurized state (after 30 times of hydrogen chloride gas vacuum substitution) and after being left to stand in a pressurized state. Thus, it can be seen that the water in the container was sufficiently removed after the hydrogen chloride gas vacuum replacement was performed 30 times.

X Cleaning device 1 High pressure gas container 11 Container body 12 Container valve 121 Handle 122 Connection part 123 Soluble plug 2 Hydrogen chloride gas supply source 3 Liquefied hydrogen chloride supply source 4 Pipes 41 to 46 Partial pipes 51 to 54 On-off valve 61 Flow rate adjustment 62 Pressure gauge 63 Pressure reducing valve 64 Pump 7 Analyzer

Claims (7)

  A method for cleaning a high-pressure gas container, comprising repeatedly performing a pressure-increasing step for introducing a hydrophilic gas into the high-pressure gas container and increasing the pressure, and an exhausting step for exhausting the gas in the high-pressure gas container.   The method for cleaning a high-pressure gas container according to claim 1, wherein a maximum pressure inside the high-pressure gas container in the pressurizing step is 0.1 MPaG or more.   The method for cleaning a high-pressure gas container according to claim 1 or 2, wherein a minimum pressure inside the high-pressure gas container in the exhausting step is equal to or lower than an atmospheric pressure. The high-pressure gas container has a fusible stopper that melts at a predetermined operating temperature or higher,
The method for cleaning a high-pressure gas container according to any one of claims 1 to 3, wherein the temperature of the high-pressure gas container is maintained at 30 ° C or higher and lower than the operating temperature in the pressurization step and the exhaust step.   The purity of the hydrophilic gas introduced into the high-pressure gas container is 99.99 vol. The method for cleaning a high-pressure gas container according to any one of claims 1 to 4, wherein the cleaning method is at least%.   The high-pressure gas according to any one of claims 1 to 5, wherein the gas having hydrophilicity is any one gas selected from the group consisting of hydrogen chloride, hydrogen bromide, chlorine, sulfur dioxide, and ammonia. Gas container cleaning method.   A high-pressure gas container that has been subjected to a cleaning treatment by the method for cleaning a high-pressure gas container according to claim 1.

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