JP4394134B2 - Cleaning method inside gas container - Google Patents

Description

  The present invention relates to a method for cleaning the inside of a gas container that removes moisture, particles, and other contaminants from a pressure-resistant gas container filled with a high-purity product gas.

  Generally, industrially used gases such as natural gas and oxygen are shipped in a pressure-resistant gas container. Such gas containers are collected and reused after the use of the gas, but when the collected empty gas container is filled with the product gas, it is appropriately subjected to a cleaning treatment, whereby the purity of the product gas, Ensures cleanliness.

  Conventionally, a heating vacuum method has been frequently used for such cleaning treatment. Specifically, while heating the gas container with an electric heater, etc., the inside of the gas container is evacuated using a vacuum pump, and moisture, particles, and other contaminants contained in the gas container are placed on the exhaust flow and discharged to the outside. The method of doing was taken.

  However, the method of continuing evacuation requires a vacuum pump with a large exhaust capacity, and it is difficult to increase the exhaust flow rate, and the gas flow in the gas container becomes a molecular flow at the end of the process. The effect of washing away the contaminants adhering to the inner wall is low.

  Therefore, in recent years, a predetermined valve (actual valve) is mounted on the valve mounting port of the gas container, and vacuum exhaust and pressure return to atmospheric pressure by nitrogen gas injection are performed a plurality of times through the actual valve (for example, Patent Document 1).

JP 2001-108588 A (paragraph 0024, FIGS. 1 and 2)

  However, according to the vacuum cleaning method disclosed in Patent Document 1, the supply and exhaust of the cleaning gas (nitrogen gas) to the gas container are alternately performed through a single real valve. A continuous high-speed air flow does not occur in the entire area, and there is a portion where the air flow is hardly generated in the gas container. Therefore, there is a problem that contaminants cannot be discharged well from the gas container.

  Moreover, in cleaning with an actual valve, the gas container cannot be heated at a high temperature in order to prevent heat deterioration of the actual valve and dissolution of the soluble metal forming the safety valve, and heating up to about 100 ° C is the limit. Therefore, it takes time to remove moisture from the gas container.

  In Patent Document 1, as a pre-process of vacuum cleaning, a tubular supply nozzle is inserted into the gas container from the valve mounting port (opening) in order to dry the gas container after the water injection pressure resistance test, Although a method of supplying dry gas into the gas container through the supply nozzle is disclosed, since the dry gas naturally flows out to the outside through the gap between the valve mounting port and the supply nozzle, it is necessary to dry the gas container. In addition to spending a lot of time and dry gas, supply of dry gas is performed with the inside of the gas container open to the atmosphere, so that the contaminants attached to the inner wall of the gas container must be desorbed by the dry gas. It is difficult.

  The present invention has been made in view of the circumstances as described above, and an object of the present invention is to provide a method that can clean the inside of a gas container well in a short time with as little cleaning gas as possible. is there.

In order to achieve the above-mentioned object, the present invention supplies and discharges a cleaning gas composed of nitrogen gas or inert gas to and from the inside of a gas container having a valve mounting port to which an actual valve is mounted at one end in the lengthwise direction. A method of cleaning the inside of the container,
In place of the actual valve, a base having an air supply port and an exhaust port is attached to the valve mounting port, and the bubble communicates with either the air supply port or the exhaust port in advance. While connecting a nozzle tube having a length reaching from the mounting port to the vicinity of the inner bottom of the gas container,
While connecting the supply source of the cleaning gas to the air supply port of the base, connecting an intake device to the exhaust port of the base,
Wherein in a state where the externally heated by a gas container with a heating device, keeping the intake system by the said gas container I forcibly evacuated by successive rows from the gas container through the exhaust port of the mouthpiece in a vacuum reduced pressure while, after intermittently supplying the cleaning gas from the supply source to the gas container through the air inlet of the mouthpiece,
The intake device is stopped and only the supply of the cleaning gas into the gas container is performed to bring the inside of the gas container to atmospheric pressure or higher, and then the base is removed and the actual valve is mounted to the valve mounting port. Features.

In addition, the inside of the gas container is cleaned by supplying and discharging a cleaning gas composed of nitrogen gas or inert gas to the inside of the gas container having a valve mounting port to which the actual valve is mounted at one end in the length direction. Yes,
In place of the actual valve, a base having an air supply port and an exhaust port is attached to the valve mounting port, and the bubble communicates with either the air supply port or the exhaust port in advance. While connecting a nozzle tube having a length reaching from the mounting port to the vicinity of the inner bottom of the gas container,
While connecting the supply source of the cleaning gas to the air supply port of the base, connecting an intake device to the exhaust port of the base,
While the gas container is heated from the outside by a heating device, forced exhaust from the gas container is continuously performed by the intake device through the exhaust port of the base, while the supply is delayed from the forced exhaust by the intake device. A cleaning gas is continuously supplied from the source into the gas container through the supply port of the base, and the supply flow rate and the exhaust flow rate by the intake device are balanced to maintain the inside of the gas container in a vacuum reduced pressure state. After continuously supplying and discharging the cleaning gas,
The intake device is stopped and only the supply of the cleaning gas into the gas container is performed to bring the inside of the gas container to atmospheric pressure or higher, and then the base is removed and the actual valve is mounted to the valve mounting port. Features.

  Further, in the gas supply / discharge process of supplying the cleaning gas from the supply source to the inside of the gas container and forcibly exhausting the gas container from the inside of the gas container, the ultrasonic wave emitted from the ultrasonic generator is emitted from the ultrasonic container. It is characterized by exciting from the outside.

  According to the present invention, a base having a supply port and an exhaust port is mounted on the valve mounting port of the gas container, and the cleaning gas is supplied and discharged through the supply port and the exhaust port. The inside of the gas container can be cleaned under vacuum and reduced pressure, so it is easy to remove moisture and other contaminants adhering to the inner wall of the gas container, and the air flow continues into the gas container through the air supply and exhaust ports. Therefore, moisture and other contaminants can be discharged well from the gas container.

  In addition, a nozzle tube having a length reaching from the valve mounting port to the vicinity of the inner bottom of the gas container is connected to either the air supply port or the exhaust port of the base mounted on the gas container. A continuous high-speed air flow is formed in the entire area of the container, and moisture and other pollutants can be discharged from the gas container in a short time, which in turn can greatly reduce the amount of cleaning gas used. it can.

  In addition, since the base instead of the actual valve is attached to the valve mounting port of the gas container for cleaning, the gas container is heated to a high temperature without worrying about the adverse effect on the actual valve due to the heating of the gas container, thereby evaporating moisture. Can be promoted and eliminated efficiently.

  In particular, while the gas container is maintained in a vacuum decompression state by forced exhaust by the intake device, the supply of the cleaning gas to the gas container is intermittently performed, or the cleaning gas is delayed in the gas container after the forced exhaust by the intake device. Is continuously supplied, and the supply flow rate and the exhaust flow rate by the intake device are balanced to maintain the inside of the gas container in a vacuum pressure-reduced state, so that the deposits are desorbed from the inner wall of the gas container. The effect can be improved.

  In addition, in the process of supplying and discharging the cleaning gas to and from the gas container, the gas container is heated from the outside by a heating device, and further, the gas container is excited from the outside by the ultrasonic waves emitted from the ultrasonic generator. Therefore, the effect of detaching the deposits from the inner wall of the gas container can be further increased.

  Hereinafter, application examples of the present invention will be described in detail with reference to the drawings. In FIG. 1, reference numeral 1 denotes a pressure-resistant gas container that is not filled with a product gas. One end in the length direction is reduced in diameter as a neck portion 1a, and the end portion is a valve mounting port 1b in which a female screw is formed on the inner periphery. As open. In addition, in order to prevent leakage of the product gas, an actual valve for sealing is mounted on the valve mounting port 1b as will be described later. However, in the present invention, the gas container 1 should be cleaned before filling with the product gas. Instead of the actual valve, a predetermined base 2 is mounted on the valve mounting port 1b.

  The base 2 is a hollow metal fitting formed with a male screw that is coupled to the female screw of the valve mounting port 1b on the outer periphery of one end, and an air supply port 2a and an exhaust port 2b are formed in that portion. In particular, one end of a nozzle tube 3 is connected to the air supply port 2a through the inside of the base 2, and the nozzle tube 3 communicates with the air supply port 2a.

  The nozzle tube 3 is a straight hard tube having corrosion resistance such as stainless steel, and its length is set to be substantially the same as the entire length of the gas container 1, and the base 2 is mounted on the valve mounting port 1 b of the gas container 1. At this time, the nozzle tube 3 passes through the center of the gas container 1 from the valve mounting port 1b to reach the vicinity of the inner bottom thereof.

  On the other hand, on the outer periphery of the base 2, manual valves 4 and 5 (for example, stop valves) are respectively attached to the air supply port 2 a and the exhaust port 2 b, and supply of cleaning gas to the air supply port 2 a via the valve 4. A source 6 is piped. The cleaning gas supply source 6 is a cylinder or a cold evaporator filled with a high-purity cleaning gas that does not substantially contain water, and the inside thereof is filled with, for example, clean nitrogen gas or liquefied nitrogen at a high pressure as the cleaning gas. ing.

  In FIG. 1, reference numeral 7 denotes an air supply line connecting the cleaning gas supply source 6 and the air supply port 2 a of the base 2, and the flow rate of the cleaning gas supplied into the gas container 1 is set in the pipe line 7. A control unit 8 for adjustment is incorporated. The control unit 8 includes a control valve 8a attached to the pipeline 7, a pressure sensor 8b, a flow rate sensor 8c, and a control unit 8d that operates the control valve 8a based on output signals of the pressure sensor 8b and the flow rate sensor 8c. Is done. The control unit 8 has two control modes (first mode and second mode). In the “first mode”, the control valve 8a is controlled to open and close based on the output signal of the pressure sensor 8b. In the “second mode”, the opening degree of the control valve 8a is adjusted so that the supply flow rate of the cleaning gas to the gas container 1 is balanced with the exhaust flow rate by the intake device 9 described later, based on the output signal of the flow rate sensor 8c. ing.

  The above-described intake device 9 is connected to the exhaust port 2b through a valve 5. In this example, the intake device 9 is a rotary vacuum pump, and its exhaust capacity is 450 L / min. In FIG. 1, reference numeral 10 denotes an exhaust pipe connecting the intake device 9 and the exhaust port 2 b of the base 2.

  Here, a specific method of cleaning the inside of the gas container 1 before filling with the product gas using the above-described base 2 will be described.

  First, the base 2 is mounted on the valve mounting port 1 b of the gas container 1, and the nozzle tube 3 communicating with the air supply port 2 a is inserted into the gas container 1. When the base 2 is mounted, the pipes 7 and 10 are disconnected from the valves 4 and 5 attached to the air supply port 2a and the exhaust port 2b, respectively, and the base 2 is firmly tightened to the valve mounting port 1b with a predetermined torque using a torque wrench or the like. Tighten to. After the cap 2 is mounted, the air supply line 7 is connected to the air supply port 2a via the valve 4, while the exhaust line 10 is connected to the exhaust port 2b via the valve 5. Thus, a gas supply / discharge process is started to clean the inside of the gas container 1.

  In the gas supply / exhaust process, first, both valves 4 and 5 are opened, and then the intake device 9 is driven to continuously forcibly exhaust gas from the inside of the gas container 1. The cleaning gas (clean nitrogen gas) is supplied from 6 through the air supply port 2 a of the base 2. According to this, the cleaning gas that has reached the air supply port 2a is discharged through the nozzle tube 3 to the bottom of the gas container 1, and is discharged from the upper part of the gas container 1 through the exhaust port 2b. A high-speed air flow from the bottom to the top is formed in the entire area. As a result, moisture and other contaminants are desorbed from the inner wall of the gas container 1 and are discharged to the outside through the exhaust port 2b in a state of being diffused into the cleaning gas.

  In particular, in the gas supply / discharge process, a method of intermittently supplying the cleaning gas and a method of continuously performing the cleaning gas are applied.

  In the method of intermittently supplying the cleaning gas, the control unit 8 is set to the “first mode”, and the intake side control is performed while continuously forcibly evacuating the gas container 1 from the gas container 1 at a constant flow rate. The cleaning gas is intermittently supplied into the gas container 1 by opening and closing the valve 8a. The control valve 8a opens when the pressure in the gas container 1 detected by the pressure sensor 8b reaches a predetermined lower limit pressure (for example, 30 hPa). It is controlled to close when it reaches a predetermined upper limit pressure (for example, 300 hPa). For this reason, the inside of the gas container 1 can be maintained in a vacuum pressure-reduced state while a high-speed air flow is formed in the entire region. .

  On the other hand, in the system in which the supply of the cleaning gas is continued, the control unit 8 is set to the “second mode”, and the intake device 9 is continuously forcedly exhausted from the gas container 1 at a constant flow rate by the intake device 9. The cleaning gas is continuously supplied into the gas container 1 behind the forced exhaust due to the above, and the supply flow rate and the exhaust flow rate by the intake device 9 are balanced to maintain the inside of the gas container 1 in a vacuum decompression state. That is, in this method, at the stage where the inside of the gas container 1 is reduced to a predetermined pressure by the forced exhaust performed in advance, the supply of the cleaning gas to the inside of the gas container 1 is started at the same flow rate as the exhaust flow rate. The supply and discharge of the cleaning gas is performed while maintaining the pressure in 1 at the pressure at the start of the supply of the cleaning gas.

  Here, in any of the above methods, since the cleaning gas is supplied and discharged while maintaining the inside of the gas container 1 in a vacuum pressure-reduced state, the vaporization of moisture adhering to the inner wall of the gas container 1 is promoted, and this is performed in the cleaning gas. Can be efficiently discharged from the gas container 1.

  In the gas supply / exhaust process as described above, the gas container 1 is accommodated in a heating device 11 (electric heater provided with a resistance heating element in a cylindrical outer body) as shown in FIG. It is preferable to heat the gas container 1 from the outside. According to this, the vaporization of moisture in the heating container 1 under low pressure is further promoted, and this is contained in the cleaning gas and efficiently discharged from the gas container 1. can do. In particular, since the actual valve is not attached to the gas container 1, the heating temperature by the heating device 11 can be increased to about 200 ° C.

  Further, in the gas supply / discharge process as described above, it is preferable that the gas container 1 is excited from the outside by the ultrasonic wave radiated from the ultrasonic generator 12. The effect of desorbing can be increased. In particular, when the gas container 1 is excited by ultrasonic waves, it is preferable to suspend the gas container 1 as shown in FIG. 1, and according to this, ultrasonic energy can be propagated satisfactorily throughout the gas container 1.

  In addition, although it is preferable to use the heating apparatus 11 and the ultrasonic generator 12 together and to heat and excite the gas container 1 at the same time, only one of them may be performed.

  Here, when the above-described cleaning process is performed for the required time, the intake device 9 is stopped and only the cleaning gas is supplied into the gas container 1 so that the inside of the gas container 1 is at atmospheric pressure (about 0.1 MPa) or more. After that, the valves 4 and 5 are closed, the pipe lines 7 and 10 are disconnected, and then the gas container 1 is taken out from the heating device 11 and is laid sideways as shown in FIG. Then, after loosening the base 2 and confirming the leakage of the cleaning gas from the gas container 1 in the process, the base 2 is removed from the valve mounting port 1b, and preferably the pipe line 7 is reconnected to the air supply port 2a at this stage. Then, the nozzle tube 3 is gradually pulled out from the gas container 1 while supplying the cleaning gas into the gas container 1 through the nozzle tube 3 inserted in the gas container 1.

  When the nozzle tube 3 is completely pulled out, the actual valve 13 is mounted on the valve mounting port 1b of the gas container 1 as shown in FIG.

  The gas container 1 to which the actual valve 13 is attached is then filled with a predetermined product gas, but the dew point in the gas container 1 is measured in order to check the cleanliness in the cleaned gas container 1. As a result, in the conventional heating vacuum method, the dew point was −79.1 ° C. at a processing time of 90 minutes, whereas in the method according to the present invention, the dew point was −90.2 ° C. at a processing time of 40 minutes. Good results have been obtained. However, in the internal cleaning of the gas container 1 used for the measurement, excitation by ultrasonic waves is not performed, the heating temperature of the gas container 1 is set to 100 ° C., which is the same as the conventional heating vacuum method, and the cleaning gas is intermittently supplied in the gas supply / discharge process. The supply method was adopted.

  Although the present invention has been described above, the cleaning gas is not limited to nitrogen gas, and argon gas or other inert gas can be used. In the above example, the nozzle tube 3 is communicated with the air supply port 2a. However, the nozzle tube 3 may be communicated with the exhaust port 2b. In this case, the gas container 1 is maintained in a vacuum-reduced state. The inside of the gas container 1 can be satisfactorily cleaned by forming a continuous high-speed air flow over the entire area.

Explanatory drawing which shows the embodiment of the washing | cleaning method which concerns on this invention Explanatory drawing which shows the state which removes a nozzle from the gas container after washing Explanatory drawing which shows the state which attached the actual valve to the gas container which cleaned

DESCRIPTION OF SYMBOLS 1 Gas container 1b Valve installation port 2 Base 2a Air supply port 2b Exhaust port 3 Nozzle pipe 6 Cleaning gas supply source 9 Intake device 11 Heating device 12 Ultrasonic generator 13 Actual valve

Claims (3)

It is a method of cleaning the inside of the gas container by supplying and discharging a cleaning gas composed of nitrogen gas or inert gas to the inside of the gas container having a valve mounting port to which the actual valve is mounted at one end in the length direction.
In place of the actual valve, a base having an air supply port and an exhaust port is attached to the valve mounting port, and the bubble communicates with either the air supply port or the exhaust port in advance. While connecting a nozzle tube having a length reaching from the mounting port to the vicinity of the inner bottom of the gas container,
While connecting the supply source of the cleaning gas to the air supply port of the base, connecting an intake device to the exhaust port of the base,
Wherein in a state where the externally heated by a gas container with a heating device, keeping the intake system by the said gas container I forcibly evacuated by successive rows from the gas container through the exhaust port of the mouthpiece in a vacuum reduced pressure while, after intermittently supplying the cleaning gas from the supply source to the gas container through the air inlet of the mouthpiece,
The intake device is stopped and only the supply of the cleaning gas into the gas container is performed to bring the inside of the gas container to atmospheric pressure or higher, and then the base is removed and the actual valve is mounted to the valve mounting port. A method for cleaning the inside of a gas container. It is a method of cleaning the inside of the gas container by supplying and discharging a cleaning gas composed of nitrogen gas or inert gas to the inside of the gas container having a valve mounting port to which the actual valve is mounted at one end in the length direction.
In place of the actual valve, a base having an air supply port and an exhaust port is attached to the valve mounting port, and the bubble communicates with either the air supply port or the exhaust port in advance. While connecting a nozzle tube having a length reaching from the mounting port to the vicinity of the inner bottom of the gas container,
While connecting the supply source of the cleaning gas to the air supply port of the base, connecting an intake device to the exhaust port of the base,
While the gas container is heated from the outside by a heating device , forced exhaust from the gas container is continuously performed by the intake device through the exhaust port of the base, while the supply is delayed from the forced exhaust by the intake device. A cleaning gas is continuously supplied from the source into the gas container through the supply port of the base, and the supply flow rate and the exhaust flow rate by the intake device are balanced to maintain the inside of the gas container in a vacuum reduced pressure state. After continuously supplying and discharging the cleaning gas,
The intake device is stopped and only the supply of the cleaning gas into the gas container is performed to bring the inside of the gas container to atmospheric pressure or higher, and then the base is removed and the actual valve is mounted to the valve mounting port. features and to Ruga scan the vessel interior cleaning method. In the gas supply / discharge process of supplying the cleaning gas from the supply source to the inside of the gas container and forcibly exhausting the gas container from the inside of the gas container, the gas container is externally exposed by ultrasonic waves emitted from an ultrasonic generator. The method for cleaning the inside of a gas container according to claim 1 or 2, wherein the gas container is excited from the outside.

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