JPH10316443A - Vitrification device of porous glass base material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vitrification device of a porous glass base material, capable of facilitating industrial recovering of helium gas at a temperature near room temperature. SOLUTION: This vitrification device of a porous glass base material has a helium gas-separation device 11 constituted of a compressor 25 for a discharged gas for pressurizing the discharged gas, plural pressure fluctuation-type helium gas absorbers 27a to 27d in parallel connection connected to an outlet of the discharged gas through inlet switch valves 26a to 26d, a common primary pressure control valve 29 connected through outlet switch valves 28a to 28d to the outlet of the pressure fluctuation-type helium gas absorbers 27a to 27d in series connection, a buffer tank 30 for helium gas connected to the outlet of the primary pressure control valve 29, a secondary pressure control valve 31 connected to the outlet of the buffer tank 30 for helium, and vent line 22 connected to the inlet switch valves 26a to 26d.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent glass preform obtained by subjecting a porous glass preform for communication or optics to a dehydration process and a transparent vitrification process in an atmosphere of a processing gas in a furnace tube. The present invention relates to a vitrification apparatus for a porous glass base material having a configuration in which helium gas is recovered from exhaust gas from a furnace tube and used repeatedly.

[0002]

2. Description of the Related Art There are a VAD method and an OVD method as means for producing a porous glass base material for an optical fiber, an image guide, a light guide, a rod lens, and the like. The base material is then dehydrated,
Through a transparent vitrification process, a transparent glass base material with almost no water content is obtained.

[0003] Such a dehydration treatment of the porous glass base material,
An apparatus for vitrifying a porous glass base material as shown in FIG.
153132).

[0004] This porous glass preform vitrification apparatus includes:
A furnace tube 1 for forming one or both of a dehydration treatment atmosphere and a transparent vitrification treatment atmosphere of the porous glass base material 2 by a treatment gas supplied from a gas inlet 1 a, and a furnace tube 1 provided on the outer periphery of the furnace tube 1. Furnace 4 provided with a heater 3 for setting a processing temperature, a gas inlet 1a and a gas outlet 1 of the furnace tube 1.
b and a circulating system 5 connected to the b.

The porous glass base material 2 is supported at the lower end of a support rod 6 and is lowered while being rotated as the support rod 6 rotates, and is subjected to a dehydration treatment and a transparent vitrification treatment separately, or to a dehydration treatment. The treatment and the transparent vitrification treatment are simultaneously performed.

The circulating system 5 includes a pretreatment device 7 for removing corrosive harmful gases such as chlorine gas from exhaust gas discharged from the gas outlet 1b, and a circulation drive of the exhaust gas treated by the pretreatment device 7. An exhaust gas buffer tank 9 for guiding and storing the exhaust gas through a source 8; a helium gas separating device 11 for guiding the exhaust gas supplied from the exhaust gas buffer tank 9 through a circulation drive source 10 to separate and recover helium gas; A helium gas buffer tank 12 for storing the recovered helium gas separated and recovered by the helium gas separator 11, a helium gas supply source 13 for supplying a new helium gas, and a recovered helium gas supplied from the helium gas buffer tank 12. For controlling the supply of new helium gas supplied from the helium gas supply source 13 to the gas inlet 1a of the furnace tube 1 A paper controller 14 is provided.

When such a circulation system 5 is used, an expensive helium gas can be recovered and reused.

[0008]

However, in such a conventional vitrification apparatus for a porous glass base material, the helium gas separation apparatus 11 has a function of separating and recovering helium gas by cooling. because there was,
There is a problem that the apparatus becomes very expensive and the running cost is high.

Further, the conventional helium gas separation apparatus 11 has a problem that it is not clear how to make the configuration industrially usable.

An object of the present invention is to provide an apparatus for vitrifying a porous glass base material, which can easily recover helium gas at around room temperature industrially.

It is another object of the present invention to provide an apparatus for vitrifying a porous glass base material capable of industrially efficiently recovering helium gas at around room temperature.

Another object of the present invention is to provide a vitrification apparatus for a porous glass base material capable of efficiently releasing an unnecessary adsorption gas in a pressure fluctuation type helium gas adsorber.

[0013]

SUMMARY OF THE INVENTION The present invention provides a furnace tube for forming either or both of an atmosphere for dehydrating a porous glass base material and an atmosphere for transparent vitrification by a gas supplied from a gas inlet. A furnace provided with a processing temperature setting heater provided on the outer periphery of the furnace tube; and a circulation system connected to a gas inlet and a gas outlet of the furnace tube, wherein the circulation system has a gas outlet of the furnace tube. The present invention is directed to an improvement of a vitrification apparatus for a porous glass base material having a helium gas separation apparatus for separating and recovering helium gas from exhaust gas discharged from a fuel cell.

[0014] One helium gas separation device used in the present invention is an exhaust gas compressor for pressurizing exhaust gas,
A plurality of pressure-variable helium gas adsorbers, which are connected in parallel to the outlet of the exhaust gas compressor via an inlet switching valve and adsorb unnecessary gas to separate and recover helium gas; And a common primary pressure control valve connected in series to the outlet of the pressure change type helium gas adsorber through an outlet switching valve to control the pressure of exhaust gas passing through each pressure-variable helium gas adsorber, and helium gas connected to the outlet of the primary pressure control valve Buffer tank, a secondary pressure control valve connected to the outlet of the helium gas buffer tank and controlling the supply pressure of the recovered helium gas supplied from the helium gas buffer tank, and an inlet switching valve. And a vent line that discharges unnecessary gas released when the pressure-variable helium gas adsorber that has absorbed unnecessary Eteiru.

Another helium gas separation apparatus used in the present invention is an exhaust gas compressor for pressurizing exhaust gas, and an exhaust gas compressor is connected in parallel to the outlet of the exhaust gas compressor via an inlet switching valve to adsorb unnecessary gas. Pressure-variable helium gas adsorbers for separating and recovering helium gas, and exhaust gas that is connected in series to the outlet of each pressure-variable helium gas adsorber through an outlet switching valve and passes through each pressure-variable helium gas adsorber A primary pressure control valve for controlling the pressure of the helium gas, a helium gas buffer tank connected to the outlet of the primary pressure control valve, and the helium gas buffer tank connected to the outlet of the helium gas buffer tank. Is connected to a secondary pressure control valve that controls the supply pressure of the recovered helium gas supplied from the pump and an outlet switching valve to absorb unnecessary gases And a vent line for discharging the unnecessary gas released to Mino pressure variable-helium gas adsorber upon the low pressure.

In these inventions, the helium gas is separated and recovered using the pressure-variable helium gas adsorber, so that the helium gas can be recovered industrially and efficiently at around room temperature. That is, when the exhaust gas is supplied at a high pressure, the pressure fluctuation type helium gas adsorber adsorbs unnecessary gas and collects it by passing helium gas. When the pressure in the vessel is lowered, the adsorbed unnecessary gas is released, and the apparatus can be reused. For this reason, by alternately using a plurality of pressure-variable helium gas adsorbers, one of the pressure-variable helium gas adsorbers can be used to adsorb unnecessary gas (when recovering helium gas) while the other pressure-variable helium gas adsorber is used. The helium gas adsorber can discharge the unnecessary gas, and the helium gas can be industrially and continuously recovered efficiently at around room temperature. Further, the cost and running cost of the apparatus can be reduced as compared with the conventional type of recovering helium gas by cooling.

Further, in these inventions, a common primary pressure control valve for controlling the pressure of the exhaust gas passing through each pressure fluctuation type helium gas adsorber is used, so that the exhaust gas passing through each pressure fluctuation type helium gas adsorber is used. Pressure control can be easily performed by the common primary pressure control valve.

In these inventions, since the helium gas buffer tank is connected to the outlet of the primary pressure control valve, the flow rate of the helium gas recovered by each pressure-variable helium gas adsorber is not constant. By storing the helium gas in the helium gas buffer tank, it is possible to continuously feed the recovered helium gas at a required flow rate.

In these inventions, since the secondary pressure control valve for controlling the supply pressure of the recovered helium gas supplied from the helium gas buffer tank is provided, the supply pressure of the recovered helium gas supplied to the core tube is provided. Can be easily controlled by the secondary pressure control valve.

Further, in these inventions, since the vent line is connected to the inlet switching valve or the outlet switching valve, the use of the vent line facilitates the release of the unnecessary gas adsorbed by the pressure fluctuation type helium gas adsorber. Can be done.

The vent line used in the present invention includes an unnecessary gas buffer tank for storing unnecessary gas flowing through the vent line, and an unnecessary gas compressor for pressurizing unnecessary gas supplied from the unnecessary gas buffer tank. A separation membrane separator for separating an impurity gas from a pressurized unnecessary gas supplied from the unnecessary gas compressor with a separation membrane, separating and recovering helium gas, and returning the helium gas to an inlet side of the exhaust gas compressor. .

When a vent line having such a structure is provided, the helium gas contained in the unnecessary gas discharged from the vent line is taken out by a separation membrane type separator, returned to the pressure fluctuation type helium gas adsorber, and collected again. can do. Therefore, the recovery rate of helium gas can be increased. In this case, the vent line is provided with an unnecessary gas buffer tank and an unnecessary gas compressor for pressurizing the unnecessary gas supplied from the unnecessary gas buffer tank. Helium gas can be stably taken out of the unnecessary gas by the separation membrane type separator.

The helium gas separation apparatus used in the present invention is composed of an exhaust gas compressor for pressurizing exhaust gas and a helium gas that is connected in parallel to the outlet of the exhaust gas compressor via an inlet switching valve to adsorb unnecessary gas. A plurality of pressure-variable helium gas adsorbers for separating and recovering gas;
A common primary pressure control valve that is connected in series to the outlet of each pressure fluctuation type helium gas adsorber via an outlet switching valve and controls the pressure of exhaust gas passing through each pressure fluctuation type helium gas adsorber, and the primary pressure control valve A helium gas buffer tank connected to the outlet of the helium gas buffer tank, and a secondary pressure control valve connected to the outlet of the helium gas buffer tank to control the supply pressure of the recovered helium gas supplied from the helium gas buffer tank. And a vent line connected to the outlet switching valve for discharging unnecessary gas released when the pressure-variable helium gas adsorber that has adsorbed the unnecessary gas is brought into a low pressure state. The vent line includes an unnecessary gas buffer tank for storing unnecessary gas flowing through the vent line, an unnecessary gas compressor for pressurizing unnecessary gas supplied from the unnecessary gas buffer tank, and a supply from the unnecessary gas compressor. A separation membrane separator is provided for separating the impurity gas from the unnecessary pressurized gas with a separation membrane, separating and recovering the helium gas, and returning the gas to the inlet side of the exhaust gas compressor.

At the outlet of the helium gas buffer tank, an inlet switching valve corresponding to the inlet of each pressure-variable helium gas adsorber is supplied with recovered helium gas supplied from the helium gas buffer tank via a check valve. A return line is connected via a return line as a purge gas.

The vitrification apparatus for a porous glass base material having such a configuration can obtain the following functions and effects in addition to the functions and effects obtained in each of the above-described inventions. That is, as in the present invention, the recovered helium gas supplied from the helium gas buffer tank is supplied to the outlet of the helium gas buffer tank through the check valve via the check valve, the inlet corresponding to the inlet of each pressure-variable helium gas adsorber. If a return line is provided as a purge gas via a switching valve, the recovered helium gas can be flowed as a purge gas into the pressure-fluxing helium gas adsorber, and the pressure-fluxing helium gas adsorber releases the unwanted gas adsorbed. The cleaning of the inside of the pressure-variable helium gas adsorber at this time can be easily performed by using the recovered helium gas that does not adversely affect the cleaning.

[0026]

FIG. 1 shows an example of a schematic configuration of an apparatus for vitrifying a porous glass base material according to the present invention. Portions corresponding to the conventional apparatus shown in FIG. The same reference numerals are given.

In this vitrification apparatus for a porous glass base material, a circulation system 5 connecting the gas outlet 1b and the gas inlet 1a of the furnace tube 1 has a cooler 15 for cooling the exhaust gas in order from the gas outlet 1b side. An exhaust gas buffer tank 9 for storing cooled exhaust gas, a pretreatment device 7 for removing corrosive harmful gases such as chlorine gas from exhaust gas supplied from the exhaust gas buffer tank 9, and a pretreatment device 7. Helium gas separator 11 for separating and recovering helium gas by guiding exhaust gas supplied from the furnace, and recovering helium gas recovered by the helium gas separator 11 and new helium gas, chlorine gas, and oxygen gas into the furnace tube 1. A gas supply controller 14 for controlling supply to the gas inlet 1a is connected, and the gas supply controller 14 supplies a helium gas to supply a newly supplied helium gas. The source 13 and the chlorine gas oxygen gas supply source for supplying a chlorine gas supply source 16 and an oxygen gas supplying 17
And are connected respectively. The gas supply controller 14
A mass flow meter 18 that measures the supply of the recovered helium gas collected by the helium gas separation device 11, a mass flow controller 19 that controls the flow rate of the newly supplied helium gas, and a flow rate of the chlorine gas that is newly supplied. The apparatus is provided with a mass flow controller 20 for performing control and a mass flow controller 21 for controlling the flow rate of newly supplied oxygen gas. The helium gas separator 11 is connected to a vent line 22 for discharging unnecessary gas. A differential pressure gauge 23 for detecting a difference between the internal pressures of the furnace tube 1 and the furnace 4 is connected thereto. A control valve 2 for controlling the pressure difference between the furnace tube 1 and the furnace 4 to be constant is provided at a gas outlet 1b.
4 are connected.

The inlet of the furnace tube 1 through which the support rod 6 passes is purged with N ₂ gas.

FIG. 2 shows the configuration of the helium gas separation device 11 used in the first example of the embodiment of the vitrification apparatus for a porous glass base material according to the present invention.

The helium gas separation device 11 comprises an exhaust gas compressor 25 for pressurizing the exhaust gas supplied from the exhaust gas storage tank 9 described above, and first to fourth four-way valves at the outlet of the exhaust gas compressor 25. First to fourth ports connected in parallel via inlet switching valves 26a to 26d to adsorb unnecessary gas and separate and recover helium gas
Pressure-variable helium gas adsorbers 27a to 27d, and the pressure-variable helium gas adsorbers 27a to 27d are connected in series via the first to fourth outlet switching valves 28a to 28d at the outlets thereof. Helium gas adsorber 2
A common primary pressure control valve 29 for controlling the pressure of the exhaust gas passing through 7a to 27d, a helium gas buffer tank 30 connected to the outlet of the primary pressure control valve 29, and an outlet of the helium gas buffer tank 30 A secondary pressure control valve 31 connected to control the supply pressure of the recovered helium gas supplied from the helium gas buffer tank 30;
A vent line 22 that is connected to the fourth inlet switching valves 26a to 26d and that discharges unnecessary gas that is released when the pressure-variable helium gas adsorbers 27a to 27d that have already adsorbed the unnecessary gas are brought into a low pressure state; It is provided with. First to fourth pressure fluctuation type helium gas adsorbers 27
Each of a to 27d is filled with an adsorbent such as zeolite which has a performance of adsorbing and separating impurities at a high pressure and releasing impurities adsorbed at a low pressure. The helium gas buffer tank 30 discharges the high-pressure gas in the first to fourth pressure-variable helium gas adsorbers 27a to 27d through the first to fourth outlet switching valves 28a to 28d. This is to perform pressure buffering.

In the vitrification apparatus for a porous glass base material provided with such a helium gas separation apparatus 11, for example, the first inlet switching valve 26a and the first outlet switching valve 28a are connected to the first pressure-variable type. Helium gas adsorber 27a
And the other second to fourth inlet switching valves 26b to 26d and the second to fourth outlet switching valves 28b to 28d are switched to the second to fourth pressure-variable helium gas adsorbers 27b. , So that the gas does not flow to the first pressure fluctuation type helium gas adsorber 27a.
Exhaust gas pressurized by the exhaust gas compressor 25 is supplied to the first pressure fluctuation type helium gas adsorber 27a so that the gas flows only in the helium gas adsorber 27a. When the pressurized exhaust gas is supplied to the first pressure-variable helium gas adsorber 27a, the unnecessary gas is adsorbed by the adsorbent, and the helium gas is passed and collected. At this time, the first pressure fluctuation type helium gas adsorber 2
The pressure of the exhaust gas passing through 7a is controlled to a required pressure by a primary pressure control valve 29. First pressure fluctuation type helium gas adsorber 2
The recovered helium gas recovered in 7a is supplied to the primary pressure control valve 29.
Through the helium gas buffer tank 30.

First pressure fluctuation type helium gas adsorber 27
a, the first inlet switching valve 26a and the first outlet switching valve 28a are switched so that gas does not flow to the first pressure-variable helium gas adsorber 27a, and the second inlet The switching valve 26b and the second outlet switching valve 28b are switched so that the gas flows to the second pressure-variable helium gas adsorber 27b, and the exhaust gas pressurized by the exhaust gas compressor 25 is subjected to the second pressure-variable helium gas. The helium gas is supplied to only the adsorber 27b, and the helium gas is recovered in the same manner.
Store to zero.

In this manner, the first to fourth pressure-variable helium gas adsorbers 27a to 27d are sequentially switched to collect helium gas and to store the helium gas in the helium gas buffer tank 3.
Store to zero.

In the first pressure-variable helium gas adsorber 27a in which the recovery of helium gas is stopped, the first inlet switching valve 26a is connected to the first pressure-variable helium gas adsorber 27a and the vent line 22. Switch to
In this state, the inside of the first pressure-variable helium gas adsorber 27a becomes a low pressure state, releases unnecessary gas adsorbed on the adsorbent, and returns to a reusable state. The released unnecessary gas is discharged through the vent line 22.

The second to the fourth where the recovery of the helium gas is stopped
Pressure fluctuation type helium gas adsorbers 27b to 27d,
In the same manner, unnecessary gas is sequentially released to return to a reusable state. The released unnecessary gases are respectively discharged through the vent lines 22.

When the helium gas is separated and recovered by using the first to fourth pressure-variable helium gas adsorbers 27a to 27d in this manner, the helium gas can be recovered industrially and efficiently at around room temperature. . That is, when the exhaust gas is supplied at a high pressure, each of the pressure fluctuation type helium gas adsorbers 27a to 27d adsorbs an unnecessary gas and collects the helium gas by passing it. When the pressure in the mold helium gas adsorbers 27a to 27d is reduced, the adsorbed unnecessary gas is released, and the helium gas adsorbers enter a reusable state. For this reason, by sequentially switching and using these pressure fluctuation type helium gas adsorbers 27a to 27d, one of the pressure fluctuation type helium gas adsorbers can be used when the unnecessary gas is adsorbed (when helium gas is recovered) while the other pressure fluctuation type helium gas adsorber is used. The pressure-fluctuation type helium gas adsorber can discharge unnecessary gas, and industrially continuously recover helium gas efficiently at around room temperature. Further, the cost and running cost of the apparatus can be reduced as compared with the conventional type of recovering helium gas by cooling.

The supply pressure of the recovered helium gas stored in the helium gas buffer tank 30 is controlled by the secondary pressure control valve 31 and supplied to the furnace tube 1 through the gas supply controller 14. At this time, if the helium gas buffer tank 30 exists before the secondary pressure control valve 31, even if the flow rate of the helium gas collected by each of the pressure-variable helium gas adsorbers 27a to 27d is not constant, the helium gas By storing the collected helium gas in the gas buffer tank 30, a required flow rate of the recovered helium gas can be continuously delivered.

FIG. 3 shows a configuration of a helium gas separation device 11 used in a second example of the embodiment of the porous glass preform vitrification device according to the present invention.
Parts corresponding to those in FIG. 2 are denoted by the same reference numerals.

In the helium gas separation device 11, an unnecessary gas buffer tank 32 for storing unnecessary gas discharged through the vent line 22 and an unnecessary gas supplied from the unnecessary gas buffer tank 32 are provided in the vent line 22. Gas compressor 33 for pressurizing the gas, and a helium gas separated and recovered by separating the impurity gas from the pressurized unnecessary gas supplied from the unnecessary gas compressor 33 by the separation membrane 34a, and the helium gas is supplied to the inlet side of the exhaust gas compressor 25. A separation membrane separator 34 for returning is provided. Other configurations are
It is the same as FIG.

The helium gas separation apparatus 1 having such a configuration
In FIG. 1, each of the pressure fluctuation type helium gas adsorbers 27a to 27
When the unnecessary gas adsorbed by the adsorbent is released through the vent line 22 by lowering the pressure in d, the unnecessary gas is temporarily stored in the unnecessary gas buffer tank 32, and the unnecessary gas buffer tank The unnecessary gas supplied from 32 is pressurized by the unnecessary gas compressor 33. The unnecessary pressurized gas supplied from the unnecessary gas compressor 33 is supplied to a separation membrane separator 34 to separate the impurity gas at the separation membrane 34a to separate and take out the helium gas. Return to the entrance side of 25.

In this way, the helium gas contained in the unnecessary gas discharged from the vent line 22 is taken out by the separation membrane type separator 34, returned to the pressure fluctuation type helium gas adsorbers 27a to 27b, and collected again. Can be. Therefore, the recovery rate of helium gas can be increased. In this case, since the vent line 22 includes the unnecessary gas buffer tank 32 and the unnecessary gas compressor 33 that pressurizes the unnecessary gas supplied from the unnecessary gas buffer tank 32, the unnecessary gas is stabilized. The helium gas can be supplied to the separation membrane separator 34 and the helium gas can be stably taken out of the unnecessary gas by the separation membrane separator 34.

Other operations, functions and effects are the same as those in FIG.

FIG. 4 shows a configuration of a helium gas separation device 11 used in a third embodiment of the vitrification apparatus for a porous glass base material according to the present invention.

The helium gas separator 11 includes an exhaust gas compressor 25 for pressurizing the exhaust gas supplied from the exhaust gas storage tank 9 described above, and first to fourth valves each having a two-way valve at the outlet of the exhaust gas compressor 25. First to fourth ports connected in parallel via inlet switching valves 26a to 26d to adsorb unnecessary gas and separate and recover helium gas
Pressure-variable helium gas adsorbers 27a to 27d, and first to fourth outlet switching valves 28 each having a two-way valve at the outlet of these pressure-variable helium gas adsorbers 27a to 27d.
a to a common primary pressure control valve 29 that is connected in series through the respective pressure variable helium gas adsorbers 27a to 27d to control the pressure of the exhaust gas passing through the respective pressure fluctuation type helium gas adsorbers 27a to 27d, and is connected to the outlet of the primary pressure control valve 29. Helium gas buffer tank 30
A secondary pressure control valve 31 connected to the outlet of the helium gas buffer tank 30 for controlling the supply pressure of the recovered helium gas supplied from the helium gas buffer tank 30; A pressure-variable helium gas adsorber 27a which is connected to the outlets of the variable helium gas adsorbers 27a to 27d via first to fourth outlet switching valves 35a to 35d each formed of a two-way valve and has already adsorbed an unnecessary gas. And a vent line 22 for discharging unnecessary gas that is released when the pressures of the valves 27 to 27d are reduced to a low pressure. First to fourth pressure fluctuation type helium gas adsorbers 27a
As described above, -27d is filled with an adsorbent such as zeolite which has the ability to adsorb and separate impurities at high pressure and release the adsorbed impurities at low pressure.

In the vent line 22, the vent line 2
An unnecessary gas buffer tank 32 for storing the unnecessary gas discharged through 2, an unnecessary gas compressor 33 for pressurizing the unnecessary gas supplied from the unnecessary gas buffer tank 32, and a supply from the unnecessary gas compressor 33. The impurity gas is separated from the unnecessary pressurized gas by the separation membrane 34a to separate and recover the helium gas, and the exhaust gas compressor 25
And a separation membrane separator 34 for returning to the inlet side of the filter.

The helium gas buffer tank 30
The recovered helium gas supplied from the helium gas buffer tank 30 is
6, a return line 39 for returning to the inlet of each of the pressure-variable helium gas adsorbers 27a to 27d is connected via a check valve 37 and first to fourth inlet switching valves 38a to 38d formed of two-way valves. Have been.

With this configuration, the following operation and effect can be obtained in addition to the operation and effect of the helium gas separation device 11 having the configuration shown in FIG. That is, in this example, the recovered helium gas supplied from the helium gas buffer tank 30 is supplied to the outlet of the helium gas buffer tank 30 via the check valve 37 at the inlet of each of the pressure-variable helium gas adsorbers 27a to 27d. Is provided as a purge gas through the inlet switching valves 38a to 38d corresponding to the pressure change type helium gas adsorbers 27a to 27c.
The helium gas adsorbers 27a to 27d can be flowed into the helium gas adsorbers 27a to 27d, and do not adversely affect the cleaning of the helium gas adsorbers 27a to 27d when the adsorbed unnecessary gas is released. It can be easily performed using the recovered helium gas.

FIG. 5 shows the valves 26a, 38a, 35a and 35a connected before and after the first pressure-variable helium gas adsorber 27a of the helium gas separator 11 shown in FIG.
FIG. 28 shows an operation timing chart of the operation 28a. In addition,
The valve 38a is opened after a DT time after the valve 35a is opened. That is, after the pressure in the pressure fluctuation type helium gas adsorber 27a decreases, the inside of the pressure fluctuation type helium gas adsorber 27a is purged using the recovered helium gas.

The valves provided before and after the pressure-variable helium gas adsorber in the other stages are also operated in the same manner when the stage is reached.

In the helium gas separation apparatus 11 of each of the above-described embodiments, the pressure-fluctuation type helium gas adsorber is provided in four stages, but the present invention is not limited to this. The adsorber can be provided by selecting an appropriate number of stages as long as it has two or more stages.

[0051]

According to the present invention, the helium gas is separated and recovered using the pressure-variable helium gas adsorber, so that the helium gas can be recovered industrially and efficiently at around room temperature. That is, when the exhaust gas is supplied at a high pressure, the pressure fluctuation type helium gas adsorber absorbs unnecessary gas and collects by passing helium gas, and when the adsorption capacity is reduced, the pressure fluctuation type helium gas adsorption device is used. When the pressure in the vessel is reduced, the adsorbed unnecessary gas can be released and returned to a reusable state. Therefore, by alternately switching and using a plurality of pressure-fluctuation type helium gas adsorbers, one of the pressure-fluctuation type helium gas adsorbers is used for adsorbing unnecessary gas (when recovering helium gas)
In addition, the other pressure-fluctuation type helium gas adsorber can release the unnecessary gas, and the helium gas can be industrially and continuously recovered efficiently at around room temperature. Further, the cost and running cost of the apparatus can be reduced as compared with the conventional type of recovering helium gas by cooling.

Also, in the present invention, since a common primary pressure control valve for controlling the pressure of the exhaust gas passing through each pressure-variable helium gas adsorber is used, the pressure of the exhaust gas passing through each pressure-variable helium gas adsorber is used. Control can be easily performed by the common primary pressure control valve.

Further, in the present invention, since the helium gas buffer tank is connected to the outlet of the primary pressure control valve, even if the flow rate of the helium gas recovered by each pressure-variable helium gas adsorber is not constant, By storing the collected helium gas in the helium gas buffer tank, a continuous flow of the recovered helium gas at a required flow rate can be performed.

Further, in the present invention, since the secondary pressure control valve for controlling the supply pressure of the recovered helium gas supplied from the helium gas buffer tank is provided, the supply pressure of the recovered helium gas supplied to the furnace tube is reduced. Control can be easily performed by the secondary pressure control valve.

Furthermore, in the present invention, since the vent line is connected to the inlet switching valve or the outlet switching valve, the unnecessary gas adsorbed by the pressure fluctuation type helium gas adsorber can be easily released by using this vent line. It can be carried out.

[Brief description of the drawings]

FIG. 1 is a partially longitudinal system diagram showing one example of a schematic configuration of a vitrification apparatus for a porous glass base material according to the present invention.

FIG. 2 is a system diagram showing a configuration of a helium gas separation device used in a first example of an embodiment of a vitrification device for a porous glass base material according to the present invention.

FIG. 3 is a system diagram showing a configuration of a helium gas separation device used in a second example of the embodiment of the porous glass preform vitrification device according to the present invention.

FIG. 4 is a system diagram showing a configuration of a helium gas separation apparatus used in a third example of the embodiment of the vitrification apparatus for a porous glass base material according to the present invention.

5 is an operation timing chart of each valve connected before and after a first pressure fluctuation type helium gas adsorber of the helium gas separation device shown in FIG.

FIG. 6 is a system diagram showing the configuration of a conventional porous glass preform vitrification apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Furnace tube 1a Gas inlet 1b Gas outlet 2 Porous glass base material 3 Heater 4 Furnace 5 Circulation system 6 Support rod 7 Pretreatment device 8 Circulation drive source 9 Exhaust gas storage tank 10 Circulation drive source 11 Helium gas separation device 12 Helium gas storage Tank 13 Helium gas supply source 14 Gas supply controller 15 Cooler 16 Chlorine gas supply source 17 Oxygen gas supply source 18 Mass flow meter 19-21 Mass flow controller 22 Vent line 23 Differential pressure gauge 24 Control valve 25 Exhaust gas compressor 26a-26d First -Fourth inlet switching valve 27a-27d First-fourth variable pressure helium gas adsorber 28a-28d First-fourth outlet switching valve 29 Primary pressure control valve 30 Helium gas buffer tank 31 Secondary pressure Control valve 32 Unnecessary gas buffer tank 33 Unnecessary gas Compressor 34 separation membrane type separators 34a separating membrane 35a~35d first to fourth outlet switching valve 36 mass flow controller 37 check valve 38a~38d first to fourth inlet switching valve 39 return line

Claims (4)

[Claims] 1. A furnace tube for forming one or both of an atmosphere for dehydrating a porous glass base material and an atmosphere for transparent vitrification by a gas supplied from a gas inlet, and a furnace tube provided on the outer periphery of the furnace tube. A furnace equipped with a heater for setting a processing temperature, and a circulation system connected to a gas inlet and a gas outlet of the furnace core tube, wherein the circulation system is provided with helium gas from exhaust gas discharged from the gas outlet. In a vitrification apparatus for a porous glass base material provided with a helium gas separation device for separating and recovering, the helium gas separation device includes an exhaust gas compressor for pressurizing the exhaust gas, and an inlet switching valve at an outlet of the exhaust gas compressor. A plurality of pressure-variable helium gas adsorbers that are connected in parallel through each other and adsorb unnecessary gas to separate and recover helium gas; A common primary pressure control valve that is connected in series to the outlet of the gaseous gas adsorber via an outlet switching valve and controls the pressure of the exhaust gas passing through each of the pressure-variable helium gas adsorbers; and an outlet of the primary pressure control valve. A helium gas buffer tank connected thereto; a secondary pressure control valve connected to an outlet of the helium gas buffer tank to control a supply pressure of the recovered helium gas supplied from the helium gas buffer tank; A vent line connected to a switching valve for discharging the unnecessary gas released when the pressure-variable helium gas adsorber that has adsorbed the unnecessary gas is set to a low pressure state. For vitreous glass base material. 2. A furnace tube for forming one or both of an atmosphere for dehydrating a porous glass base material and an atmosphere for transparent vitrification by a gas supplied from a gas inlet, and a furnace tube provided on the outer periphery of the furnace tube. A furnace equipped with a heater for setting a processing temperature, and a circulation system connected to a gas inlet and a gas outlet of the furnace core tube, wherein the circulation system is provided with helium gas from exhaust gas discharged from the gas outlet. In a vitrification apparatus for a porous glass base material provided with a helium gas separation device for separating and recovering, the helium gas separation device includes an exhaust gas compressor for pressurizing the exhaust gas, and an inlet switching valve at an outlet of the exhaust gas compressor. A plurality of pressure-variable helium gas adsorbers that are connected in parallel through each other and adsorb unnecessary gas to separate and recover helium gas; A common primary pressure control valve that is connected in series to the outlet of the gaseous gas adsorber via an outlet switching valve and controls the pressure of the exhaust gas passing through each of the pressure-variable helium gas adsorbers; and an outlet of the primary pressure control valve. A helium gas buffer tank connected thereto; a secondary pressure control valve connected to an outlet of the helium gas buffer tank to control a supply pressure of the recovered helium gas supplied from the helium gas buffer tank; A vent line connected to a switching valve for discharging the unnecessary gas released when the pressure-variable helium gas adsorber that has adsorbed the unnecessary gas is set to a low pressure state. For vitreous glass base material. 3. An unnecessary gas buffer tank for storing the unnecessary gas flowing through the vent line, an unnecessary gas compressor for pressurizing the unnecessary gas supplied from the unnecessary gas buffer tank, A separation membrane separator for separating an impurity gas from a pressurized unnecessary gas supplied from the unnecessary gas compressor with a separation membrane to separate and recover helium gas and returning the gas to the inlet side of the exhaust gas compressor; The vitrification apparatus for a porous glass base material according to claim 1 or 2, wherein: 4. A furnace tube for forming one or both of a dehydration treatment atmosphere and a transparent vitrification treatment atmosphere of a porous glass base material by a gas supplied from a gas inlet, and a furnace tube provided on an outer periphery of the furnace tube. A furnace equipped with a heater for setting a processing temperature, and a circulation system connected to a gas inlet and a gas outlet of the furnace core tube, wherein the circulation system is provided with helium gas from exhaust gas discharged from the gas outlet. In a vitrification apparatus for a porous glass base material provided with a helium gas separation device for separating and recovering, the helium gas separation device includes an exhaust gas compressor for pressurizing the exhaust gas, and an inlet switching valve at an outlet of the exhaust gas compressor. A plurality of pressure-variable helium gas adsorbers that are connected in parallel through each other and adsorb unnecessary gas to separate and recover helium gas; A common primary pressure control valve that is connected in series to the outlet of the gaseous gas adsorber via an outlet switching valve and controls the pressure of the exhaust gas passing through each of the pressure-variable helium gas adsorbers; and an outlet of the primary pressure control valve. A helium gas buffer tank connected thereto; a secondary pressure control valve connected to an outlet of the helium gas buffer tank to control a supply pressure of the recovered helium gas supplied from the helium gas buffer tank; A vent line connected to a switching valve for discharging the unnecessary gas released when the pressure-variable helium gas adsorber that has adsorbed the unnecessary gas is put into a low pressure state, and the vent line is provided with the vent An unnecessary gas buffer tank for storing the unnecessary gas flowing through the line, and an unnecessary gas supplied from the unnecessary gas buffer tank. A compressor for unnecessary gas to be pressurized, and a separation membrane type separation for separating an impurity gas from a pressurized unnecessary gas supplied from the unnecessary gas compressor by a separation membrane to separate and recover helium gas and returning the gas to the inlet side of the exhaust gas compressor. A helium gas buffer tank is provided at an outlet thereof. The helium gas buffer tank is provided with a recovered helium gas supplied from the helium gas buffer tank via a check valve corresponding to an inlet of each of the pressure fluctuation type helium gas adsorbers. An apparatus for vitrifying a porous glass base material, wherein a return line for returning as a purge gas is connected via an inlet switching valve.