JP6195082B2 - Method for removing moisture from high-pressure gas container - Google Patents

Description

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

  In a high-pressure gas container into which product gas is newly added or a high-pressure gas container that has been pressure-resistant tested by water pressure (hereinafter sometimes simply referred to as “gas container”), the container valve is connected to the container body in the atmosphere. Installation work is performed. For this reason, the water | moisture content in air | atmosphere will mix in the inside of a gas container. If the product gas is filled with moisture mixed in the gas container, the purity standard required for the product gas cannot be satisfied.

  In particular, regarding the moisture, it was difficult to remove due to its adsorptivity even though the product purity standard was 0.5 ppm or less, and thus the inside of the gas container had to be sufficiently dried.

  Incidentally, Patent Document 1 is known as a method for drying the inside of a gas container. This Patent Document 1 discloses a method of introducing a heated gas such as water vapor or heated air to heat and dry the inside of the gas container, expelling the water vapor or the like with compressed air, and then cooling and sealing the gas container. Yes.

  However, in the method disclosed in Patent Document 1, the inside of the gas container is heated and dried before the container valve is attached. Therefore, when the container valve is attached, air is mixed in the gas container and is included in the air. There was a problem that a quantity of moisture remained attached to or adsorbed on the inner wall surface of the gas container.

  For this reason, when a high-purity product gas is filled in the gas container, the purity of the product gas cannot be maintained due to the moisture remaining in the gas container, and the container is again used after the heating and drying process or before filling the product gas. It was necessary to repeat the process of removing the moisture inside. Moreover, even if the process of removing the water in the container is repeated, it is actually difficult to satisfy the product standard for the purity of the product gas.

Japanese Patent No. 3995372

  On the other hand, a container valve used for a high-pressure gas container is required to have a function of reliably blocking high-pressure gas, and the opening degree when the container valve is fully opened is limited. For this reason, there has been a problem that the efficiency of evacuation deteriorates if the gas container is evacuated through the container valve after the container valve is attached to the gas container.

  Particularly in the process of evacuating the gas container, a high vacuum region is preferable in order to reduce residual impurities. However, in the pressure region lower than the medium vacuum region, the exhaust rate of water vapor in the gas container is also slowed down. An evacuation of time was required. Furthermore, there is a problem that a lot of energy such as equipment including heating of the cylinder, electric power, and manpower is required.

  This invention is made | formed in view of the said situation, and makes it a subject to provide the water | moisture-content removal method in a high pressure gas container which can implement | achieve sufficient dry state efficiently in a short time.

In order to solve this problem, the present invention has the following configuration.
That is, the invention according to claim 1 is a method for removing moisture in a high-pressure gas container to which a container valve is attached, through the container valve until the pressure in the high-pressure gas container becomes 1 to 500 Pa. And a second step of filling the high-pressure gas container with the cleaning gas through the container valve until the pressure in the high-pressure gas container becomes 2 kPa or more and less than 100 kPa. And removing the water in the high-pressure gas container by repeating the first step and the second step in a state where the high-pressure gas container is heated.

  The invention according to claim 2 is the method of removing moisture in the high-pressure gas container according to claim 1, wherein heating is performed so that the temperature of the outer surface of the high-pressure gas container is in a range of 60 to 70 ° C.

  The invention according to claim 3 is the method of removing moisture in the high-pressure gas container according to claim 1 or 2, wherein the water content of the cleaning gas is less than 0.1 ppm.

  The invention according to claim 4 is the method of removing moisture in the high-pressure gas container according to any one of claims 1 to 3, wherein the first step and the second step are repeated three or more times.

  The method for removing moisture in a high-pressure gas container according to the present invention comprises a high-pressure gas container through a container valve until the pressure in the high-pressure gas container becomes 1 to 500 Pa in a state where the high-pressure gas container to which the container valve is attached is heated. By repeatedly performing the first step of exhausting the inside and the second step of filling the high-pressure gas container with the cleaning gas through the container valve until the pressure in the high-pressure gas container becomes 2 kPa or more and less than 100 kPa, The inside of the high-pressure gas container can be sufficiently dried efficiently and in a short time.

It is a systematic diagram which shows the structure of the water | moisture-content removal apparatus in the high pressure gas container applicable to the moisture removal method in the high pressure gas container which is one Embodiment to which this invention is applied. It is a flowchart which shows the moisture removal method in the high pressure gas container which is one Embodiment to which this invention is applied.

  Hereinafter, a water removal method in a high-pressure gas container, which is an embodiment to which the present invention is applied, will be described in detail with reference to the drawings together with a water removal device in a high-pressure gas container using the same. In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent.

FIG. 1 shows a water removal apparatus (hereinafter referred to as a water removal device) in a high pressure gas container that can be applied to a water removal method in a high pressure gas container (hereinafter sometimes simply referred to as “moisture removal method”) that is an embodiment to which the present invention is applied. FIG. 2 is a system diagram showing the configuration of the “water removal device”.
As shown in FIG. 1, the moisture removing device 1 is for processing a gas container (high pressure gas container) 2 to which a container valve 2A is attached, and a heating device (heating means) for heating the gas container 2 3), a thermometer (temperature measuring means) 4 (4A, 4B, 4C) for measuring the surface temperature of the gas container 2, a main path L1 connected to the container valve 2A and communicating with the inside of the gas container 2, and a gas A pressure gauge (pressure measuring means) 5 for measuring the pressure inside the container 2, a vacuum pump (decompression means) 6 for evacuating the inside of the gas container 2 and the main path L1, and the inside of the gas container 2 and the main path A cleaning gas supply path L2 for supplying a cleaning gas into L1, a cleaning gas discharge path L3 for discharging the cleaning gas filled in the gas container 2 and the main path L1, and a gas container 2 connected to the main path L1 Of the cleaning gas filled in the main path L1 A sampling path L4 to obtain the part, provided with a moisture meter provided in the sampling path L4 (the moisture measuring means) 7, a, is schematically configured.

  The gas container 2 is a container for filling and storing a high-pressure gas, and a high-pressure gas container before a new product gas is introduced or a high-pressure gas container that has been subjected to a pressure test by water pressure is a processing target. .

  Although it does not specifically limit as a material of the gas container 2, Specifically, stainless steel, manganese steel, aluminum etc. are mentioned, for example.

  Although it does not specifically limit as a size of the gas container 2, Specifically, the thing of 10-48L is mentioned, for example.

  The container valve 2A is not particularly limited, but the material, the outer diameter of the cap portion, the screw direction, and the like can be appropriately selected according to the component of the product gas filled in the gas container 2.

  The heating device 3 is not particularly limited as long as at least the entire gas container 2 can be heated. Specific examples of the heating device 3 include a heating furnace that can accommodate the entire gas container 2 and heat the internal space, and a heater that directly wraps around the surface of the gas container 2. .

  The thermometer 4 is not particularly limited as long as it can measure the surface temperature of the gas container 2. Moreover, it is preferable to provide a plurality of thermometers 4 in order to simultaneously measure a plurality of locations on the surface of the gas container 2. Specifically, for example, as shown in FIG. 1, among the outer surfaces of the gas container 2, a thermometer 4A that measures the shoulder, a thermometer 4B that measures the trunk, and a thermometer 4C that measures the bottom. Are preferably provided. Thereby, the gas container 2 can be heated more appropriately according to the temperature distribution in the gas container 2.

The main path L1 is a main path for drying the inside of the gas container 2. The main path L1 has one end connected to the container valve 2A and the other end connected to the vacuum pump 6. As a result, the main path L1 and the gas container 2 communicate with each other, and the vacuum pump 6 can evacuate the gas container 2 and the main path L1. Further, the main path L1 is off valve V ₁ on one end side, on-off valve V ₅ are respectively provided on the other end.

  The material of the main path L1 is not particularly limited as long as it has heat resistance, pressure resistance, and corrosion resistance. Specific examples of such a material include stainless steel piping. Further, as the diameter of the main path L1, it is preferable to use a diameter of 1/2 inch or more in consideration of exhaust efficiency.

Pressure gauge 5, in order to measure the pressure inside of the gas container 2, and is connected to the main path L1 via an on-off valve V _3. The installation place of the pressure gauge 5 is not particularly limited as long as the pressure inside the gas container 2 can be measured. For example, as shown in FIG. 1, the pressure in the gas container 2 may be monitored by monitoring the pressure in the main path L1 by measuring the pressure in the main path L1, or connected to the container valve 2A. The pressure in the gas container 2 may be directly measured.

  The vacuum pump 6 is not particularly limited as long as the vacuum pump 6 can evacuate the inside of the gas container 2 and the inside of the main path L1 to the middle vacuum region (specifically, 1 Pa or less). Specific examples of such a vacuum pump 6 include a dry pump type.

The cleaning gas supply path L2 is a piping path for supplying the cleaning gas into the gas container 2 and the main path L1. The cleaning gas supply path L2 has one end connected to a cleaning gas supply source (not shown) and the other end connected to the main path L1 (or branched from the main path L1). Furthermore, the cleaning gas supply path L2 is off valve V ₂ is provided.

  The cleaning gas is not particularly limited as long as it contains a small amount of moisture and can remove moisture in the gas container 2. Specific examples include high-purity nitrogen and high-purity helium having a water content of less than 0.1 ppm.

The cleaning gas discharge path L3 is a piping path for discharging the cleaning gas filled in the gas container 2 and the main path L1. The cleaning gas discharge path L3 has one end connected to the main path L1 (or branched from the main path L1) and the other end open to the atmosphere. Furthermore, the cleaning gas vent path L3 is off valve V ₄ is provided. According to this cleaning gas discharge path L3, by the pressure in the gas container 2 and the main path L1 is opened to close valve V ₄ is higher than the atmospheric pressure, the gas container 2 and the main-path L1 The cleaning gas filled in can be discharged out of the system.

The sampling path L4 is a piping path for acquiring a part of the cleaning gas filled in the gas container 2 and the main path L1. The sampling path L4 has one end connected to the main path L1 (or branched from the main path L1) and the other end open to the atmosphere. Further, the sampling path L4, on-off valve V ₆ is provided.

Moisture meter 7, the sampling path L4, is provided on the secondary side of the opening and closing valve V _6. The moisture meter 7 is not particularly limited as long as it can measure the moisture concentration in the cleaning gas filled in the gas container 2 and the main path L1. Specific examples of the moisture meter 7 include a crystal oscillation type and a cavity ring down type.

Further, the moisture removing device 1 includes a control device (control means) (not shown). This control device is configured to open and close the on-off valves V _{1 to} V ₆ according to the indicated values of the thermometer 4 (4A, 4B, 4C) and the pressure gauge 5, respectively.

  Next, the water removal method of this embodiment using the water removal apparatus 1 described above will be described in detail. FIG. 2 is a flowchart showing a preparation process for filling a product gas into a high-pressure gas container, including the water removal method of the present embodiment.

  In the method of filling the high-pressure gas container with the product gas, first, as shown in step S1 in FIG. 2, the inside of the gas container 2 is visually observed as a first step. Specifically, first, in a state where the container valve 2A is not yet attached to the gas container 2, rust and dirt on the inner surface of the container are visually confirmed using an endoscope as necessary. If the degree of rust or dirt can be confirmed by visual observation, it will be disposed of. On the other hand, when it is determined that it can be reused, acid cleaning or the like is separately performed, and it is visually observed again. In the first step, the gas container 2 is not attached with the container valve 2A, so the inside of the gas container 2 is in the same state as the atmospheric atmosphere.

  Next, as shown in step S2 in FIG. 2, the container valve 2A is attached to the gas container 2 as a second step. Specifically, the valve is tightened until the specified torque is reached, and the container valve 2 </ b> A is attached to the gas container 2. Thereby, the inside and the outside of the gas container 2 are partitioned (blocked) by the container valve 2A.

  Next, as shown in step S <b> 3 in FIG. 2, drying in the gas container 2 (that is, the water removal method of the present embodiment) is performed as a third step.

Drying in the gas container 2 is performed by the first to fifth sub-steps as shown in FIG.
First, the first sub-process shown in step S3-1 in FIG. 2 is a process of performing replacement with the cleaning gas in the gas container 2 and the main path L1. Specifically, first, the container valve 2A of the gas container 2 is in the closed state, the opening and closing valve _{V 1} open state, the on-off valve _{V 2, V 3, V 4} , V 5, V 6 is closed. Then, the container valve 2A in order to release the residual gas in the gas container 2 opened, the on-off valve V ₄ open. Next, confirm that there is no more gas flow to the on-off valve V ₄ and the container valve 2A in the closed state.

Next, in order to reduce the moisture mixed in the piping system and adsorbed on the surface of the piping when the container valve 2A is attached to the gas container 2, the content of moisture is less than 0.1 ppm as a cleaning gas. Perform replacement work. Specifically, first, on-off valve V ₂ in the open state, after introducing a pressure which is previously set high-purity nitrogen in the gas container 2 and inside the main path L1 (e.g., 2 to 3 MPa), on-off valve the V ₂ in the closed state. Next, in order to release high-purity nitrogen to the gas container 2 and inside the main path L1 becomes the atmospheric pressure, on-off valve V ₄ opened, after the release is completed, the on-off valve V ₄ and the closed state To do. Thus, by opening and closing operations of the on-off valve V ₂ and the on-off valve V _4, by performing a plurality of times substituted work by high purity nitrogen (e.g. 10 times), water was mixed into the gas container 2 and the main-path L1 Reduce the amount.

  Next, the 2nd sub process shown to step S3-2 in FIG. 2 is a process of heating the gas container 2. FIG. Specifically, heating is started by operating the heating device 3. Here, the heating temperature of the high-pressure gas container by the heating device 3 is preferably 60 ° C. or higher and lower than 100 ° C. Next, the respective temperatures of the shoulder portion, the trunk portion, and the bottom portion of the outer surface of the gas container 2 are measured by the thermometers 4A to 4C, and when each temperature falls within the range of 60 to 70 ° C., a control device (not shown) The output (heating temperature) of the heating device 3 is controlled so as to maintain this temperature range. In this way, by heating the gas container 2 with the heating device 3, the moisture adsorbed on the surface in the gas container 2 can be desorbed.

Next, the third sub-process shown in step S3-3 in FIG. 2 is a process (first step) for evacuating the inside of the gas container 2 (and the main path L1). Specifically, first activates the vacuum pump 6, and the opening and closing valve V ₁ and closing valve V ₅ to the open state and starts the evacuation of the gas container 2 and the main-path L1. Next, the opening and closing valve V ₃ after evacuation has been initiated by the open state, to start the measurement of the degree of vacuum in the gas container 2 and the main-path L1 by the pressure gauge 5. Here, evacuation is performed until the pressure in the gas container 2 and the main path L1 reaches an arbitrary set value (for example, 1 Pa) in the medium vacuum region (1 to 500 Pa). Thus, by evacuating the inside of the gas container 2, the moisture desorbed by heating can be discharged from the high-pressure gas container 2 and the main path L1.

  If the pressure in the gas container 2 is made to reach a high vacuum region of less than 1 Pa with the container valve 2A attached (that is, via the container valve 2A), the exhaust time becomes very long. Each energy is wasted. For this reason, it is sufficient to evacuate to the middle vacuum region in the third sub-step in the moisture removal method of the present embodiment. Thereby, exhaust time can be shortened.

Next, the fourth sub-process shown in step S3-4 in FIG. 2 is a vacuum region batch replacement process in which the inside of the gas container 2 and the main path L1 are repeatedly filled with the cleaning gas and evacuated. . Specifically, first, stopping the evacuation of the gas container 2 off valve V ₅ in the closed state. Then the on-off valve V ₂ to the open state, high purity nitrogen is introduced into the inner gas container 2 (and the main-path L1), any set of less than the pressure in the gas container 2 is more than 2 kPa 100 kPa as the cleaning gas Fill until a value (for example, 10 kPa) is reached (second step). Then, the pressure gauge 5 indicated value, confirm that the pressure in the gas container 2 has reached the arbitrary set value, the on-off valve V ₂ are closed, high-purity nitrogen gas (cleaning into the gas container 2 Stop filling gas.

Next, the opening and closing valve _{V 5} to the open state, any set value of the pressure in the gas container 2 and the main-path L1 is 1 to 500 Pa (e.g., 100 Pa) by performing evacuation until, in the gas container 2 Then, the cleaning gas in the main path L1 is discharged (first step). Then, confirm that the indicated value of the pressure gauge 5 reaches the arbitrary set value, stop the evacuation of the gas container 2 off valve V ₅ as closed. By repeating such an operation three or more times (for example, five times), the moisture in the gas container 2 can be sufficiently reduced even when the heating temperature of the gas container 2 is in the range of 60 ° C. to 70 ° C. it can.

  By the way, when the set value (100 Pa in the above example) of the vacuum side (low pressure side) pressure in the vacuum region batch replacement step is performed in a lower pressure region, the ability to remove moisture is increased, but the time required for evacuation Becomes longer. For this reason, the total energy required for operation and heating of the vacuum pump increases, and the total process time also becomes longer.

  Moreover, when the set value (10 kPa in the above example) of the pressure side (high pressure side) pressure in the vacuum region batch replacement process is performed in a higher pressure region, the water dilution ratio increases, but the moisture gas container 2 reaches the inner wall. This is not efficient because re-adsorption occurs at the same time and the time required for evacuation of the next process becomes longer. Therefore, in the vacuum region batch replacement step, it is possible to increase the efficiency by repeating a plurality of operations rather than widening the difference between the low pressure side pressure and the high pressure side pressure.

Next, the 5th sub process shown to step S3-4 in FIG. 2 is a process of cooling the gas container 2. FIG. More specifically, first, after the fourth sub-step (vacuum region batch replacement step) is complete, continue to the opening and closing valve V ₅ to the open state to continue the evacuation of the gas container 2. Next, when it is confirmed that the indicated value of the pressure gauge 5 has reached 1 Pa, for example, heating of the gas container 2 by the heating device 3 is stopped and cooling is started. When each of the thermometers 4A~4C becomes less than 50 ° C., the on-off valve V ₅ are closed, then the on-off valve V ₃ is closed state, terminates the vacuum evacuation.

  Next, the gas container 2 is taken out from the heating device 3 to dissipate heat. For example, in the conventional method for removing moisture from a gas container, the gas container is heated at 100 ° C. or higher. However, in the moisture removing method of the present embodiment, heating is performed at 60 to 70 ° C. Shorter. Thereby, production efficiency can be raised.

  Next, as shown in step S <b> 4 in FIG. 2, as a fourth step, the high-pressure gas container 2 from which moisture removal has been completed is filled with a desired product gas. Through the above steps, the water content becomes 0.5 ppm or less, and the purity standard required for the product gas can be satisfied.

  As described above, according to the water removal method of the present embodiment, the container valve 2A is heated until the pressure in the gas container 2 becomes 1 to 500 Pa in a state where the gas container 2 to which the container valve 2A is attached is heated. The process of evacuating the gas container 2 through the container and the process of filling the gas container 2 with the cleaning gas through the container valve 2A are repeated until the pressure in the gas container 2 becomes 2 kPa or more and less than 100 kPa. Thereby, the inside of the gas container 2 can be maintained in a sufficiently dry state. Therefore, the working time can be shortened and the heating energy can be reduced, so that productivity can be improved.

  The effects of the present invention will be described below using examples and comparative examples.

Example 1
While using the water removal apparatus 1 shown in FIG. 1, the water removal method shown in FIG. 2 was performed.
In the first sub-process shown in step S3-1 in FIG. 2, high-purity nitrogen having a water content of less than 0.1 ppm was used as the cleaning gas, and the replacement operation with high-purity nitrogen was performed 10 times.
Next, in the second sub-process shown in step S3-2 in FIG. 2, the respective temperatures of the shoulder, trunk, and bottom of the outer surface of the gas container 2 are measured by the thermometers 4A to 4C. The heating temperature was controlled so as to be in the range of 60 to 70 ° C.
Next, in the third sub-process shown in Step S3-3 in FIG. 2, vacuum evacuation was performed until the pressure in the gas container 2 and the main path L1 became 1 Pa.
Next, in the fourth sub-process (vacuum area batch replacement process) shown in step S3-4 in FIG. 2, the vacuum side (low-pressure side) pressure is set to 100 Pa, the vacuum is evacuated, and the pressure side (high-pressure side) ) The pressure was set to 10 kPa and the cleaning gas was filled. Note that high purity nitrogen having a water content of less than 0.1 ppm was used as the cleaning gas. In addition, the number of repetitions of the vacuum region batch replacement step was five.
Next, in the 4th sub process shown to step S3-5 in FIG. 2, when the pressure in the gas container 2 became 1 Pa, heating was stopped and cooling was started. Next, when the temperature of the gas container 2 became less than 50 ° C., the evacuation was finished.

After completion of cooling, the on-off valve V ₂ is opened condition, a high purity nitrogen gas was charged with 0.5MPa to gas container 2. Next, the open state of the opening and closing valve V _6, the amount of water contained in the high purity nitrogen gas filled was measured by moisture meter 7, the water content was less than 90 ppb. The total process time from the start of heating to the end of cooling was 2 hours 30 minutes.
The results are shown in Table 1 below.

(Comparative Example 1)
In the said Example 1, it processed using the same conditions except having changed the lower limit of the pressure area | region which implements a vacuum area | region batch substitution process to 10 Pa, and an upper limit to 100 kPa.
After completion of cooling, high-purity nitrogen gas was charged at 0.5 MPa in the same manner as in Example 1. As a result, a moisture content of 0.7 ppm was detected by the moisture meter 7. The total process time from the start of heating to the end of cooling was 2 hours 30 minutes.
The results are shown in Table 1 below.

(Comparative Example 2)
As a conventional method for removing moisture in a gas container, in the example described in Patent Document 1 described above, the moisture concentration when filling up to 0.5 MPa was −74.0 ° C. (1.4 ppm). The total process time from the start of heating to the end of cooling was 26 hours or more.
The results are shown in Table 1 below.

  As shown in Table 1, in the pressure range as in Comparative Example 1, it was confirmed that the moisture in the gas container could not be sufficiently removed, and the dew point of the product was greatly increased.

  On the other hand, in Example 1, compared with Comparative Example 1 and Comparative Example 2, it has an extraordinary water removal capability, and the time required from heating to cooling including vacuum evacuation is greatly reduced. It was confirmed that

DESCRIPTION OF SYMBOLS 1 ... Water | moisture-content removal apparatus, 2 ... Gas container (high pressure gas container), 2A ... Container valve, 3 ... Heating device (heating means), 4, 4A, 4B, 4C ... Thermometer (temperature measurement means), 5 ... Pressure gauge (Pressure measuring means), 6 ... vacuum pump (pressure reducing means), 7 ... moisture meter (moisture measuring means), L1 ... main path, L2 ... cleaning gas supply path, L3 ... cleaning gas discharge path, L4 ... sampling path, V _{1 to} V ₆ ... Open / close valve

Claims (4)

A method for removing moisture in a high-pressure gas container to which a container valve is attached,
A first step of evacuating the high-pressure gas container through the container valve until the pressure in the high-pressure gas container becomes 1 to 500 Pa;
Filling the high-pressure gas container with a cleaning gas through the container valve until the pressure in the high-pressure gas container is 2 kPa or more and less than 100 kPa, and
A method for removing moisture in a high-pressure gas container, wherein the first step and the second step are repeated while the high-pressure gas container is heated.   The method for removing moisture in a high-pressure gas container according to claim 1, wherein heating is performed so that the temperature of the outer surface of the high-pressure gas container is in a range of 60 to 70 ° C.   The method for removing moisture in a high-pressure gas container according to claim 1 or 2, wherein the cleaning gas has a water content of less than 0.1 ppm.   The method for removing moisture in a high-pressure gas container according to any one of claims 1 to 3, wherein the first step and the second step are repeated three or more times.

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