JP6943802B2 - Plumbing equipment - Google Patents

Description

The present invention relates to a piping device capable of preventing liquefaction and gelation of the raw material gas and supplying the raw material gas to the burner side even if the flow rate change and the mixing ratio of the raw material gas supplied from the vaporizer change.

In recent years, glass base materials for optical fibers have been increasing in size in order to improve productivity. The glass base material for an optical fiber is produced by a well-known method such as a VAD (Vapor Phase Axial Deposition) method, a MCVD (Modified Chemical Vapor Deposition) method, or an OVD (Outside Vapor Deposition) method.

For example, in Patent Document 1, a starting rod and a burner for generating fine glass particles are installed in a reaction vessel, a raw material gas is introduced into the burner via a supply pipe, and the raw material gas is thermally decomposed and oxidized in a flame formed by the burner. The reaction is carried out to generate glass fine particles, and the generated glass fine particles are deposited on a starting rod to prepare a glass fine particle deposit (glass base material for fiber). In the OVD method, for example, the raw material gas supplied to the burner is siloxane, and the burner is heated so that the temperature of the burner is in the range of -30 ° C or higher and + 30 ° C or lower with respect to the boiling point of the siloxane, and the temperature of the supply pipe is increased. The supply pipe is heated so that the temperature is above the boiling point of the siloxane and below the boiling point of + 30 ° C.

Japanese Unexamined Patent Publication No. 2014-224007

By the way, as described above, the mixed gas of the vaporized raw material such as siloxane and the carrier gas is liquefied unless it is kept at a temperature higher than the boiling point, while excessive heating causes gelation due to the polymerization reaction. The temperature control range is very narrow. Therefore, when the mixed gas leaves the vaporizer, it is heated to a temperature equal to or higher than the boiling point of the mixed gas, but in order to avoid gelation, it is controlled not to heat to a temperature higher than necessary. Then, the mixed gas exiting the vaporizer is guided by the burner and ejected as a gas from the burner.

However, it is difficult to directly connect the vaporizer to the burner due to physical restrictions, and it is necessary to connect with a pipe of a certain length. Therefore, it is necessary to heat the pipe over the entire length of the pipe.

Since it is necessary to control the temperature at the burner introduction port to a temperature at which the mixed gas is ejected from the tip of the burner without being liquefied, the lower limit temperature at the burner introduction port is determined. However, if the mixed gas is heated excessively, the polymerization reaction proceeds, so that the upper limit temperature is determined by adding + 30 ° C. to the boiling point, for example. In addition, it is necessary to control the entire area of the pipe at a temperature at which it does not liquefy and does not gel. Therefore, it is necessary to control the entire pipe in a narrow predetermined temperature range.

Here, when the flow rate of the mixed gas flowing through the pipe increases, if the temperature is controlled by the inlet temperature of the pipe, the raw material gas on the outlet side of the pipe is overheated and the risk of gelation increases, and the outlet of the pipe increases. If the temperature is controlled by the temperature, the temperature on the inlet side is lowered and the raw material gas is easily liquefied.

Further, since the liquefaction temperature of the raw material gas changes depending on the mixing ratio of the raw material gas and the carrier gas, it is necessary to surely keep the raw material gas above the boiling point.

In Patent Document 1, the supply pipe is heated so that the temperature of the supply pipe is in the range of the boiling point of siloxane or higher and the boiling point of + 30 ° C. or lower, but it is not easy to control the temperature in the narrow temperature range as described above. No.

The present invention has been made in view of the above, and even if the flow rate change and the mixing ratio of the raw material gas supplied from the vaporizer change, the raw material gas is prevented from being liquefied and gelled and supplied to the burner side. It is an object of the present invention to provide a piping device which can be used.

In order to solve the above-mentioned problems and achieve the object, the piping device according to the present invention is a piping device in which a mixed gas of a raw material gas and a carrier gas supplied from a vaporizer flows through a pipe and is supplied to a burner side. The area where the pipes are arranged is divided into a front stage region and a rear stage region, and the front stage heater that heats the pipes in the front stage region, the rear stage heater that heats the pipes in the rear stage region, and the pipes in the front stage region. Based on the detection results of the pre-stage temperature sensor that measures the inlet temperature, the post-stage temperature sensor that measures the outlet temperature of the pipe in the rear-stage region, and the pre-stage temperature sensor, the temperature at the inlet of the pipe is the boiling point temperature of the raw material gas. As described above, the temperature at the outlet of the pipe is set based on the detection results of the pre-stage temperature control unit that controls the temperature using the pre-stage heater and the post-stage temperature sensor so as to be equal to or lower than the upper limit temperature obtained by adding the margin temperature to the boiling point temperature. It is characterized by including a post-stage temperature control unit that controls the temperature by using the post-stage heater so that the temperature is equal to or higher than the boiling point temperature of the raw material gas and equal to or lower than the upper limit temperature obtained by adding the margin temperature to the boiling point temperature.

Further, the piping device according to the present invention is characterized in that, in the above invention, the maximum heating output of the front stage heater is larger than the maximum heating output of the rear stage heater.

Further, in the piping device according to the present invention, in the above invention, the front stage heater and the rear stage heater are ribbon heaters wound around the piping, and the front stage heater has a smaller winding pitch than the rear stage heater. It is characterized by.

Further, the piping device according to the present invention is characterized in that, in the above invention, the front stage heater and the rear stage heater are inclined so that the heat generation density becomes smaller toward the burner side.

Further, in the above invention, the piping device according to the present invention provides an intermediate region between the front region and the rear region, and heats the pipe in the intermediate region with the intermediate heater and the temperature of the pipe in the intermediate region. Based on the detection results of the intermediate temperature sensor and the intermediate temperature sensor, the intermediate heater is set so that the temperature of the pipe is equal to or higher than the boiling point temperature of the mixed gas and equal to or lower than the upper limit temperature obtained by adding the margin temperature to the boiling point temperature. It is characterized by further providing an intermediate temperature control unit for controlling the temperature using the above.

Further, the piping device according to the present invention is characterized in that, in the above invention, the upper limit temperature is an upper limit temperature at which gelation of the raw material gas does not occur.

Further, the piping device according to the present invention is characterized in that, in the above invention, the raw material gas is siloxane and the margin temperature is 30 ° C.

According to the present invention, even if the flow rate change and the mixing ratio of the raw material gas supplied from the vaporizer change, the raw material gas can be prevented from being liquefied and gelled and supplied to the burner side.

FIG. 1 is a schematic view showing a configuration of a piping device according to an embodiment of the present invention. FIG. 2 is a diagram showing a temperature change of the mixed gas in the pipe when the flow rate of the inflowing mixed gas changes. FIG. 3 is a diagram showing a conventional temperature change of the mixed gas in the pipe when the flow rate of the inflowing mixed gas changes. FIG. 4 is a schematic view showing the configuration of a piping device according to a modification 1 of the embodiment of the present invention. FIG. 5 is a schematic view showing the configuration of a piping device according to a modification 2 of the embodiment of the present invention.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a schematic view showing a configuration of a piping device 1 according to an embodiment of the present invention. As shown in FIG. 1, the piping device 1 has a piping 10 that connects between the vaporizing device 2 and the burner 3 and supplies the mixed gas from the vaporizing device 2 side to the burner 3 side. The mixed gas is a mixture of siloxane, which is a raw material gas vaporized by the vaporizer 2, specifically, octamethylcyclotetrasiloxane, and a carrier gas, which is an inert gas such as argon gas.

The pipe 10 is divided into a front stage region E1 in which the front stage heater 13 is arranged and a rear stage region E2 in which the rear stage heater 14 is arranged at the pipe intermediate point P3. The front stage heater 13 is a ribbon heater wound around the pipe 10 in the front stage region E1. The rear heater 14 is a ribbon heater wound around the pipe 10 in the rear region E2. The maximum heating output of the front heater 13 is larger than the maximum heating main force of the rear heater 14.

The pre-stage temperature sensor 11 is a thermocouple and is arranged in contact with the pipe inlet P1 of the pipe 10 to measure the inlet temperature of the pipe 10. The subsequent temperature sensor 12 is a thermocouple and is arranged in contact with the pipe outlet P2 of the pipe 10 to measure the outlet temperature of the pipe 10.

The temperature control unit 20 includes a front temperature control unit 21, a rear temperature control unit 22, a front heater power supply unit 23, and a rear heater power supply unit 24. The pre-stage temperature control unit 21 energizes and controls the pre-stage heater power supply unit 23 so that the temperature measured by the pre-stage temperature sensor 16 is within a predetermined temperature range, and controls the heating of the pre-stage heater 13. The predetermined temperature range is equal to or higher than the boiling point of siloxane and lower than the upper limit temperature obtained by adding the margin temperature (30 ° C.) to the boiling point. The rear-stage temperature control unit 22 controls the energization of the rear-stage heater power supply unit 24 so that the temperature measured by the rear-stage temperature sensor 17 is within a predetermined temperature range, and controls the heating of the rear-stage heater 14. That is, the temperature control for the front region E1 and the temperature control for the rear region E2 are performed independently.

FIG. 2 is a diagram showing a temperature change of the mixed gas in the pipe 10 when the flow rate of the inflowing mixed gas changes. In FIG. 2, the temperature change at the time of a small flow rate is shown by the curve L1, and the temperature change at the time of a large flow rate is shown by the curve L2. As shown in FIG. 2, even if the flow rate of the mixed gas is different, the temperature of the pipe inlet P1 in which the front temperature sensor 11 is arranged maintains the boiling point T1 or higher, and the temperature of the pipe outlet P2 in which the rear temperature sensor 12 is arranged is maintained. The temperature does not exceed the upper limit temperature T2, which is the boiling point T1 plus the margin temperature 30 ° C. As a result, the inflowing mixed gas can suppress gelation in the pipe 10.

Further, when the flow rate is large, the front stage heater 13 in the front stage region E1 has a larger heating maximum output than the rear stage heater 14, so that the raw material gas is surely maintained at the boiling point T1 or higher in the front stage region E1 to prevent liquefaction. Can be done. On the other hand, since the temperature of the mixed gas in the latter region E2 is controlled at the pipe outlet, the temperature can be easily controlled so as not to exceed the upper limit temperature.

Therefore, in the present embodiment, even if the flow rate change and the mixing ratio of the raw material gas supplied from the vaporizer change, the raw material gas can be prevented from being liquefied and gelled and supplied to the burner side.

As shown in FIG. 3, when the temperature of the mixed gas in the pipe is controlled by one heater and one temperature sensor, if the inflowing mixed gas has a small flow rate, the mixed gas is kept within a predetermined temperature range. Although it can be stored (see curve L101), when the inflowing mixed gas has a large flow rate and the temperature control point is the pipe inlet, the amount of heat is large and the heat is transferred to the pipe on the subsequent stage side. However, the outlet temperature exceeds the upper limit temperature, which promotes gelation of the raw material gas (see curve L103).

On the other hand, when the inflowing mixed gas has a large flow rate and the temperature control point is the pipe outlet, the heating amount on the pipe inlet side cannot be increased, and sufficient heating cannot be performed, so that the raw material Gas liquefaction may occur (see curve L102).

<Modification example 1>
FIG. 4 is a schematic view showing the configuration of the piping device 1a, which is a modification 1 of the embodiment of the present invention. As shown in FIG. 4, in the piping device 1a, the same ribbon heater is wound around the pipe 10 in the front stage region E1 and the rear stage region E2, but the pitch of the front stage heater 33 in the front stage region E1 is changed to the rear stage heater in the rear stage region E2. It is smaller than the pitch of 34. That is, in the first modification, the maximum heating output of the heater can be set depending on the difference in the winding pitch of the ribbon heater.

<Modification 2>
FIG. 5 is a schematic view showing the configuration of the piping device 1b, which is a modification 2 of the embodiment of the present invention. As shown in FIG. 5, the piping device 1b is divided into three stages in which an intermediate region E3 is provided between the front region E1 and the rear region E2, instead of the two stages of the front region E1 and the rear region E2. The temperature is controlled individually. Similar to the embodiment, the front stage region E1 and the rear stage region E2 are provided with the front stage temperature sensor 11 and the rear stage temperature sensor 12 at the pipe inlet P1 and the pipe outlet P2, respectively, and the intermediate region E3 is provided with the intermediate region E3. An intermediate temperature sensor 40 is provided at an arbitrary position on the inner pipe 10. The maximum heating output of the front heater 41, the intermediate heater 42, and the rear heater 43 provided in the front region E1, the intermediate region E3, and the rear region E2 is sequentially reduced.

In this modification 2, since the region is divided into three stages, finer temperature control becomes possible.

The heaters in each region, such as the front heater 13 and the rear heater 14, may be inclined so that the heat generation density becomes smaller toward the burner 3 side in the region. As a result, finer temperature control can be performed.

Further, in the above-described embodiments and modifications 1 and 2, siloxane is mentioned as an example of the raw material to be vaporized, but the present invention is not limited to this, and can be applied to _{, for example, silicon tetrachloride (SiCl 4).} ..

Although the embodiment to which the invention made by the present inventors has been applied has been described above, the present invention is not limited by the description and the drawings which form a part of the disclosure of the present invention according to the present embodiment. That is, other embodiments, examples, operational techniques, and the like made by those skilled in the art based on the present embodiment are all included in the scope of the present invention.

1,1a, 1b Piping device 2 Vaporizer 3 Burner 10 Piping 11 Front temperature sensor 12 Rear temperature sensor 13, 33, 41 Front heater 14, 34, 43 Rear heater 16 Front temperature sensor 17 Rear temperature sensor 20 Temperature control unit 21 Front stage Temperature control unit 22 Rear temperature control unit 23 Front heater power supply unit 24 Rear heater power supply 40 Intermediate temperature sensor 42 Intermediate heater E1 Front region E2 Rear region E3 Intermediate region L1, L2 Curve P1 Pipe inlet P2 Pipe outlet P3 Pipe intermediate point T boiling point T1 boiling point T2 upper limit temperature

Claims (6)

It is a piping device that flows a mixed gas of a raw material gas and a carrier gas supplied from a vaporizer through a pipe and supplies it to the burner side.
The area where the pipe is arranged is divided into a front-stage area and a rear-stage area.
A pre-stage heater that heats the piping in the pre-stage region,
A post-stage heater that heats the piping in the post-stage region,
A pre-stage temperature sensor that measures the inlet temperature of the pipe in the pre-stage region,
A post-stage temperature sensor that measures the outlet temperature of the piping in the post-stage region,
Based on the detection result of the pre-stage temperature sensor, the temperature is controlled by using the pre-stage heater so that the temperature at the inlet of the pipe is equal to or higher than the boiling point temperature of the raw material gas and equal to or lower than the upper limit temperature obtained by adding the margin temperature to the boiling point temperature. Pre-stage temperature control unit and
Based on the detection result of the latter stage temperature sensor, the temperature is controlled by using the latter stage heater so that the temperature at the outlet of the pipe is equal to or higher than the boiling point temperature of the mixed gas and equal to or lower than the upper limit temperature obtained by adding the margin temperature to the boiling point temperature. Post-stage temperature control unit and
Equipped with a,
The margin temperature is a temperature obtained by subtracting the boiling point temperature of the raw material gas from the temperature at which the mixed gas does not gel.
A piping device characterized in that the temperature rise gradient due to temperature control of the rear stage temperature control unit using the rear stage heater is smaller than the temperature rise gradient of temperature control by the front stage temperature control unit using the front stage heater. It is a piping device that flows a mixed gas of a raw material gas and a carrier gas supplied from a vaporizer through a pipe and supplies it to the burner side.
The area where the pipe is arranged is divided into a front-stage area and a rear-stage area.
A pre-stage heater that heats the piping in the pre-stage region,
A post-stage heater that heats the piping in the post-stage region,
A pre-stage temperature sensor that measures the inlet temperature of the pipe in the pre-stage region,
A post-stage temperature sensor that measures the outlet temperature of the piping in the post-stage region,
Based on the detection result of the pre-stage temperature sensor, the temperature is controlled by using the pre-stage heater so that the temperature at the inlet of the pipe is equal to or higher than the boiling point temperature of the raw material gas and equal to or lower than the upper limit temperature obtained by adding the margin temperature to the boiling point temperature. Pre-stage temperature control unit and
Based on the detection result of the latter stage temperature sensor, the temperature is controlled by using the latter stage heater so that the temperature at the outlet of the pipe is equal to or higher than the boiling point temperature of the mixed gas and equal to or lower than the upper limit temperature obtained by adding the margin temperature to the boiling point temperature. Post-stage temperature control unit and
With
The margin temperature is a temperature obtained by subtracting the boiling point temperature of the raw material gas from the temperature at which the mixed gas does not gel.
A piping device characterized in that the maximum heating output of the first-stage heater is larger than the maximum heating output of the second-stage heater. The front heater and the rear heater are ribbon heaters that are wound around the pipe.
The piping device according to claim 2, wherein the front-stage heater has a smaller winding pitch than the rear-stage heater. The piping device according to any one of claims 1 to 3, wherein the front-stage heater and the rear-stage heater are inclined so that the heat generation density becomes smaller toward the burner side. An intermediate region is provided between the front region and the rear region.
An intermediate heater that heats the piping in the intermediate region,
An intermediate temperature sensor that measures the temperature of the piping in the intermediate region,
An intermediate temperature whose temperature is controlled by using the intermediate heater so that the temperature of the pipe is equal to or higher than the boiling point temperature of the mixed gas and equal to or lower than the upper limit temperature obtained by adding the margin temperature to the boiling point temperature based on the detection result of the intermediate temperature sensor. Control unit and
The piping device according to any one of claims 1 to 4, further comprising. The raw material gas is siloxane and
The piping device according to any one of claims 1 to 5, wherein the margin temperature is 30 ° C.

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