JP2020142214A - Gaseous starting material supply method and gaseous starting material supply apparatus - Google Patents

Abstract

To provide a gaseous starting material supply method and a gaseous starting material supply apparatus allowing for prevention of blockage of piping due to gelatinization of a gaseous starting material and thereby allowing for stable supply of the gaseous starting material.SOLUTION: There is provided the gaseous starting material supply method for supplying gaseous starting material into a supply destination 16, the method comprises the steps of: measuring a weight of a liquefaction raw material charged into a raw material vessel 12; gasifying the liquefied raw material by heating thereby generating a gaseous starting material; supplying the generated gaseous starting material into a supply destination 16 through raw material supply piping 18; heating the raw material supply piping 18 by a heater 38 thereby maintaining a gasified state of the gaseous starting material: measuring a flow rate of the gaseous starting material in the raw material supply piping 18; and controlling a temperature of the heater 38 so that a difference between a reduction of the weight of the liquefied raw material and a weight of the gaseous starting material obtained by conversion from an integrated value of the measured flow rate falls within a prescribed range.SELECTED DRAWING: Figure 1

Description

The present invention relates to a raw material gas supply method and a raw material gas supply device.

Conventionally, in order to stably synthesize an optical fiber preform, even if the vaporized raw material (raw material gas) fluctuates slightly, the flow rate of combustion gas is changed in conjunction with the fluctuation of the raw material, and the surface temperature at which the suit is deposited is constant. It is common to control so that Further, it is known that the lower limit temperature of the pipe is specified so that the vaporized raw material does not agglomerate or reliquefy, and the upper limit temperature is specified so as not to overheat (excessive heat is applied) and kept constant within that range.

By the way, as the equipment becomes larger, the length of the pipe after vaporization becomes longer, and if it is used for a long period of time, the heater may deteriorate or the heat insulating material may deteriorate, causing local heating shortage, where coagulation and reliquefaction may occur. May occur. In that case, the flow rate of the raw material changes, but the production can be continued as it is by controlling the surface temperature, for example (see, for example, Patent Document 1). The raw material reliquefied in the pipe moves to the downstream side due to the vaporized raw material flowing in the pipe, and if it stays there for a long time, it may gel due to overheating (see, for example, Patent Document 2).

Tokusho 4-13299 Gazette Japanese Unexamined Patent Publication No. 2014-224007

The gelled raw material generally has a high boiling point, which makes it difficult to vaporize and eventually causes clogging of the pipe. In that case, the conditions cannot be controlled to be constant by controlling the combustion gas or the like, and naturally the production cannot be continued. In addition, once blocked, the equipment cannot be operated for a long time, and the cost of reconstructing the piping is required. Therefore, if there is a function of detecting liquefaction, which is the primary cause, the risk of secondary damage due to gelation or the like can be avoided, but liquefaction cannot be detected by the technique of Patent Document 2.

The present invention has been made in view of the above, and provides a raw material gas supply method and a raw material gas supply device capable of preventing blockage of a pipe due to gelation of the raw material gas and stably supplying the raw material gas. The purpose is to provide.

In order to solve the above-mentioned problems and achieve the object, the raw material gas supply method according to the present invention is a method of supplying the raw material gas to the supply destination, and is a step of measuring the weight of the liquefied raw material contained in the raw material container. The process of generating vaporized raw material gas by heating the liquefied raw material, the process of supplying the generated raw material gas to the supply destination through the raw material supply pipe, and the vaporization state of the raw material gas by heating the raw material supply pipe with a heater. Difference between the process of maintaining the above, the process of measuring the flow rate of the raw material gas in the raw material supply pipe, the reduced amount of the measured weight of the liquefied raw material, and the weight of the raw material gas obtained by converting from the integrated value of the measured flow rate. It is characterized by having a step of controlling the temperature of the heater so that the temperature falls within a predetermined range.

Further, another raw material gas supply method according to the present invention is characterized in that, in the above-described invention, it has a step of vaporizing the liquefied raw material to generate a raw material gas by heating the raw material container.

Further, in the other raw material gas supply method according to the present invention, in the above-mentioned invention, the inside of the raw material container is pressurized to supply the liquefied raw material to the raw material supply pipe, and the raw material supply pipe is heated by a heater to care for the liquefied raw material. It is characterized by having a step of forming a raw material gas.

Further, the raw material gas supply device according to the present invention is a device that supplies the raw material gas to the supply destination, and has a weight measuring mechanism for measuring the weight of the liquefied raw material in the raw material container and vaporization by heating the liquefied raw material. A heating mechanism that generates the raw material gas, a raw material supply pipe that supplies the generated raw material gas to the supply destination, a heater that heats the raw material supply pipe to maintain the vaporization state of the raw material gas, and a raw material gas in the raw material supply pipe. The heater so that the difference between the flow rate measuring mechanism that measures the flow rate and the weight reduction of the measured liquefied raw material and the weight of the raw material gas obtained by converting from the integrated value of the measured flow rate is within a predetermined range. It is characterized by having a control mechanism for controlling the temperature.

Further, in the other raw material gas supply device according to the present invention, in the above-described invention, the heating mechanism is characterized in that the raw material gas is generated by heating the raw material container.

Further, in the other raw material gas supply device according to the present invention, in the above-described invention, the heating mechanism includes a pressurizing mechanism for pressurizing the raw material container and a heater for heating the liquefied raw material supplied to the raw material supply pipe. It is characterized by being.

Further, in the above-described invention, another raw material gas supply device according to the present invention has a gas avoidance pipe branched from the raw material supply pipe and connected via an on-off valve in the vicinity of the raw material container, and this gas avoidance pipe is provided. Is characterized by being connected to a gas treatment facility.

Further, in the other raw material gas supply device according to the present invention, in the above-described invention, the difference between the measured reduction in the weight of the liquefied raw material and the weight of the raw material gas obtained by converting from the integrated value of the measured flow rate is It is characterized by having at least one of an alarm mechanism for notifying when a predetermined value is exceeded and an avoidance mechanism for opening an on-off valve to avoid the raw material gas in the gas avoidance pipe.

According to the present invention, the temperature of the heater is controlled so that the difference between the measured reduction in the weight of the liquefied raw material and the weight of the raw material gas obtained by converting from the integrated value of the measured flow rate is within a predetermined range. Therefore, it is possible to prevent agglomeration of the raw material gas, an extreme change in the flow rate due to reliquefaction, and blockage of the raw material supply pipe due to gelation. Therefore, the raw material gas can be stably supplied.

FIG. 1 is a schematic configuration diagram showing Example 1 of the raw material gas supply device according to the present invention. FIG. 2 is a diagram showing a modified example of the first embodiment. FIG. 3 is a diagram showing a change in weight of the raw material used in Example 1. FIG. 4 is a diagram showing a change in Wc of Example 1. FIG. 5 is a schematic configuration diagram showing Example 2 of the raw material gas supply device according to the present invention. FIG. 6 is a diagram showing a change in Wc of Example 2. FIG. 7 is a diagram showing changes in Wc of the comparative example.

Hereinafter, the raw material gas supply method and the embodiment of the raw material gas supply device according to the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

As shown in FIG. 1, the raw material gas supply device 10 according to the present embodiment supplies a raw material extending from a constant temperature bath 14 containing the raw material container 12 and a burner (supply destination) 16 for generating glass fine particles from the raw material container 12. It includes a pipe 18, a flow rate measuring device 20 provided in the middle of the raw material supply pipe 18 and functioning as a mass flow controller, and a control mechanism 22.

A weight measuring mechanism 24 capable of measuring the weight of the raw material container 12 is installed at the bottom of the constant temperature bath 14, and a heating mechanism 26 having a heating control function is provided around the constant temperature bath 14. In the present embodiment, the weight measuring mechanism 24 is composed of a load cell, and the heating mechanism 26 is composed of a heater.

On the upstream side of the raw material supply pipe 18, a pipe 28 for sending nitrogen gas to the raw material supply pipe 18 and a gas avoidance pipe for discharging the raw material gas of the raw material supply pipe 18 to the exhaust gas treatment device 30 (gas treatment equipment). 32 are connected. The pipe 28 and the gas avoidance pipe 32 are provided with on-off valves 34 and 36 for adjusting the passing flow rate, respectively. Further, a heater 38 for heating these is provided around the raw material supply pipe 18 and the gas avoidance pipe 32. A thermocouple 40 for measuring the temperature of the raw material supply pipe 18 is provided in the vicinity of the raw material supply pipe 18.

The control mechanism 22 is connected to the weight measuring mechanism 24, the heating mechanism 26, the heater 38, the thermocouple 40, the flow rate measuring device 20, and the on-off valves 34 and 36, and each operation can be controlled by transmitting and receiving data.

The raw material gas can be generated by heating the raw material container 12 with the heating mechanism 26 and vaporizing the liquefied raw material in the raw material container 12. The heating mechanism of the present invention is not limited to this, and for example, as shown in FIG. 2, a pressurizing mechanism 42 that pressurizes the raw material container 12 and a heater that heats the liquefied raw material supplied to the raw material supply pipe 18. The heating mechanism may be configured with 38. The pressurizing mechanism 42 can be composed of a pipe 44 for feeding nitrogen gas or the like into the raw material container 12. In this way, the inside of the raw material container 12 is pressurized with nitrogen gas or the like, the liquefied raw material in the raw material container 12 is guided to the raw material supply pipe 18, and the liquefied raw material is vaporized by the heater 38 that heats the raw material supply pipe 18. It is possible to generate a raw material gas.

Next, examples of the present invention will be described.

(Example 1)
In Example 1, siloxane (octamethylcyclotetrasiloxane having a melting point of 17.5 ° C. and a boiling point of 175 ° C. (hereinafter referred to as OMCTS)) was used as a liquefying raw material. OMCTS was placed in a raw material container 12 having a known weight, and the weight of the initial OMCTS was measured by a load cell (weight measuring mechanism 24) and found to be 35.6 kg. This measured value is taken into the control mechanism 22 as data.

The OMCTS was vaporized by setting the initial temperature to 200 ° C., which is higher than the boiling point of the OMCTS, by using the constant temperature bath 14 and the heater 38 of the raw material supply pipe 18. The vaporized OMCTS flows through the mass flow controller (flow measuring device 20), and the OMCTS gas is ejected into the hydrogen acid flame generated by the separately supplied flammable gas and flammable gas, and the silicon oxide is oxidized by the thermal decomposition oxidation reaction. (SiO ₂ ) Synthesize particles.

While the raw material was being supplied, the weight loss Wa (reduced amount) was measured from the initial weight of the raw material measured in the load cell and the weight of the current OMCTS measured in the load cell. Further, in the OMCTS, the time and the flow rate flowing through the mass flow controller are taken into the control mechanism 22 and converted into the weight. This converted weight was defined as Wb. In the control mechanism 22, the temperature of the heater 38 of the raw material supply pipe 18 was adjusted so that Wc = Wa−Wb became constant.

FIG. 3 shows the time change of the raw material used as the time change of Wa and Wb. FIG. 4 shows the time change of Wc. As shown in these figures, Wc does not change with the passage of time except at the initial stage when the raw material supply pipe 18 is filled with the vaporized raw material. From this, it can be seen that the raw material is stably supplied in the raw material supply pipe 18 without liquefaction.

Therefore, according to the present embodiment, it is possible to prevent agglomeration of the raw material gas, an extreme change in the flow rate due to reliquefaction, blockage of the raw material supply pipe 18 due to gelation, and the like. Therefore, the raw material gas can be stably supplied.

(Example 2)
In the second embodiment, when Wc exceeds a predetermined value (specified value 1), the on-off valve 36 of the gas avoidance pipe 32 is opened to avoid the raw material gas of the raw material supply pipe 18 to the gas avoidance pipe 32. It is equipped with. The avoidance mechanism is realized by the operation of the control mechanism 22. In the second embodiment, as shown in FIG. 5, by controlling a part of the heater A of the raw material supply pipe 18 independently from the control mechanism 22, the temperature is set to 220 ° C., which is higher than the boiling point of OMCTS. The raw material gas was supplied in the same manner as in Example 1.

FIG. 6 shows the time change of Wc. As shown in this figure, the behavior was initially the same as that of the first embodiment, but it started to increase slightly in the middle and exceeded the specified value 1, so the avoidance mechanism was activated and connected to the raw material supply pipe 18. The on-off valve 36 of a gas avoidance pipe 32 was opened, and the raw material gas was avoided by the exhaust gas treatment device 30. The heating mechanism 26 of the constant temperature bath 14 in which the raw material container 12 is housed and the heater 38 of the raw material supply pipe 18 also stopped heating and were naturally cooled, and the liquefied raw material was collected in the raw material container 12. After the equipment was stopped, the raw material supply pipe 18 was investigated, but the gelled OMCTS could not be confirmed.

(Comparison example)
Next, a comparative example will be described.
FIG. 7 shows the time change of Wc by setting the specified value 2. As shown in this figure, the behavior was initially the same as that of the second embodiment, but when the use was continued as it was, the Wc value suddenly increased, so the heating was manually stopped and connected to the raw material supply pipe 18. The on-off valve 36 of the gas avoidance pipe 32 was opened to avoid the raw material gas to the exhaust gas treatment device 30. The heating mechanism 26 of the constant temperature bath 14 in which the raw material container 12 is housed and the heater 38 of the raw material supply pipe 18 were also naturally cooled, and the liquefied raw material was recovered in the raw material container 12. After the equipment was stopped, the raw material supply pipe 18 was investigated, and a gel-like OMCTS was confirmed.

As described above, according to the present embodiment, the difference between the measured reduction in the weight of the liquefied raw material and the weight of the raw material gas obtained by converting from the integrated value of the measured flow rate is within a predetermined range. Since the temperature of the heater 38 is controlled in this way, it is possible to prevent agglomeration of the raw material gas, an extreme change in the flow rate due to reliquefaction, blockage of the raw material supply pipe 18 due to gelation, and the like. Therefore, the raw material gas can be stably supplied.

In the second embodiment, the case where the on-off valve 36 is opened to avoid the raw material gas in the gas avoidance pipe 32 when the Wc exceeds a predetermined value is provided as an example. Is not limited to this, and may have an alarm mechanism for notifying when Wc exceeds a predetermined value, or may have both the alarm mechanism and the avoidance mechanism.

10 Raw material gas supply device 12 Raw material container 14 Constant temperature bath 16 Burner for producing glass fine particles (Supply destination)
18 Raw material supply piping 20 Flow measuring device 22 Control mechanism 24 Weight measuring mechanism 26 Heating mechanism 28,44 Piping 30 Exhaust gas treatment equipment (gas treatment equipment)
32 Gas avoidance piping 34, 36 On-off valve 38 Heater 40 Thermocouple 42 Pressurizing mechanism

Claims (8)

It is a method of supplying raw material gas to the supply destination.
The process of measuring the weight of the liquefied raw material in the raw material container, the process of generating the vaporized raw material gas by heating the liquefied raw material, the process of supplying the generated raw material gas to the supply destination through the raw material supply pipe, and the raw material. The process of heating the supply pipe with a heater to maintain the vaporized state of the raw material gas, the process of measuring the flow rate of the raw material gas in the raw material supply pipe, the amount of decrease in the weight of the measured liquefied raw material, and the integrated value of the measured flow rate. A method for supplying a raw material gas, which comprises a step of controlling the temperature of the heater so that the difference from the weight of the raw material gas obtained by converting from the above is within a predetermined range. The raw material gas supply method according to claim 1, further comprising a step of vaporizing the liquefied raw material to generate a raw material gas by heating the raw material container. The first aspect of claim 1 is characterized by having a step of pressurizing the inside of the raw material container to supply the liquefied raw material to the raw material supply pipe, and heating the raw material supply pipe with a heater to vaporize the liquefied raw material to generate a raw material gas. The raw material gas supply method described. A device that supplies raw material gas to the supply destination,
A weight measuring mechanism that measures the weight of the liquefied raw material in the raw material container, a heating mechanism that generates vaporized raw material gas by heating the liquefied raw material, and a raw material supply pipe that supplies the generated raw material gas to the supply destination. A heater that heats the raw material supply pipe to maintain the vaporized state of the raw material gas, a flow rate measuring mechanism that measures the flow rate of the raw material gas in the raw material supply pipe, a decrease in the weight of the measured liquefied raw material, and the measured flow rate. A raw material gas supply device characterized by having a control mechanism for controlling the temperature of a heater so that the difference from the weight of the raw material gas obtained by converting from the integrated value is within a predetermined range. The raw material gas supply device according to claim 4, wherein the heating mechanism generates a vaporized raw material gas by heating the raw material container. The raw material gas supply device according to claim 4, wherein the heating mechanism includes a pressurizing mechanism for pressurizing the raw material container and a heater for heating the liquefied raw material supplied to the raw material supply pipe. Claims 4 to 6 include a gas avoidance pipe branched from a raw material supply pipe and connected via an on-off valve in the vicinity of the raw material container, and the gas avoidance pipe is connected to a gas treatment facility. The raw material gas supply device according to any one of the above. An alarm mechanism and an on-off valve that notify when the difference between the measured weight reduction of the liquefied raw material and the weight of the raw material gas obtained by converting from the integrated value of the measured flow rate exceeds a predetermined value. The raw material gas supply device according to any one of claims 4 to 7, further comprising at least one of an avoidance mechanism for avoiding the raw material gas in the gas avoidance pipe.

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