JP5263214B2 - Gas gate valve for high temperature furnace - Google Patents

Description

  The present invention relates to a high-temperature furnace gas gate valve used in an apparatus related to an industry that handles various high-temperature gases such as a coke oven.

  In a coke oven for iron making, coal dry distillation gas (COG) generated during the dry distillation of coal is recovered by a collecting pipe and used as fuel. At this time, since the generated COG is a high temperature up to about 850 ° C., it is theoretically possible to recover the sensible heat of the gas to save energy. However, COG contains tar, which is a high-boiling point gas, and has the property that tar condenses when the temperature of COG falls below 700 ° C. Once condensed, the properties of the tar change after condensation and often change to a substance that does not evaporate easily even if overheated again. COG also has the property that carbon contained in the form of hydrocarbons such as methane is decomposed at a high temperature of 700 ° C. or higher and is precipitated as solid carbon (soot) (this phenomenon is called coking). The solid carbons once precipitated are also strongly bonded to each other, so that they are not easily hydrocarbonated even when the temperature is lowered again.

  In the prior art, if high-temperature COG is circulated, a large amount of such tar or solid carbon adheres to the COG contact surface of the pipeline equipment (pipe, valve, blower, etc.). The operation becomes difficult. For this reason, conventionally, when COG generated in a coke oven is discharged from the riser pipe of the coke oven, it is immediately cooled to water and brought to room temperature. At this time, since the tar is condensed and separated from the COG and mixed with the cooling water to be removed, only the low boiling point gas (referred to as dry COG) in the normal temperature COG has been recovered as fuel. Since dry COG has no particular operational problems, general industrial pipeline equipment can be applied, and the gas flow in the pipeline can be freely controlled.

  On the other hand, in the riser, COG must come into contact with a gas from which tar has not been removed (referred to as wet COG), and therefore coking on the inner surface of the riser is inevitable. In addition, COG may be lowered in temperature in a series of coal carbonization processes, and at this time, the condensate of tar in COG may adhere to the inner wall surface of the rising pipe and form a firm fixed layer. Since these deposits continue to increase as the operation continues, the riser pipe line is blocked, and therefore, the riser pipe line burns out carbon adhering to the inner face of the riser pipe every predetermined short period, for example, every day. Requires work. Such problems of tar adhesion and coking that occur in the riser pipe are not limited to the riser pipe, but are common problems in the pipeline system for circulating wet COG.

Further, in the wet COG, soot dust having a diameter of several μm to several mm derived from powdered coal is suspended at a high concentration of, for example, 1 g / m ³ or more. For this reason, even if a precise mechanical seal is applied to the wet COG, there is a problem that the dust easily bites into the seal portion and extremely deteriorates the sealing performance.

  For this reason, in the prior art, COG was quickly cooled with water with almost no sensible heat of COG being used due to problems of tar adhesion, coking, and dust in the gas. For example, in the method of installing a flow rate adjustment valve between the riser and the drain main shown in Patent Document 1, the COG flowing through the flow rate adjustment valve is already cooled by spray water spraying, and Since the flow rate control valve alone cannot block the gas flow, a separate water seal valve is required. Patent Document 2 discloses a shutoff valve for wet COG, but in this device, both the valve seat and the valve box continue to contact the wet COG, and intense coking and tar condensation and solidification on these surfaces can be avoided. There is no need for frequent cleaning work. Further, in Patent Document 3, an exhaust pipe is provided in an ascending pipe, and exhaust air is recovered by heating air circulating in the air pipe by a high-temperature COG flow in the ascending pipe. However, in this apparatus, if the cooling amount of COG is large, COG immediately condenses and solidifies on the air piping surface as tar and disturbs heat transfer and causes a problem of blocking the riser pipe. There is a problem that only a part can be collected.

  In this way, when using high-temperature wet COG sensible heat, rather than aiming to recover exhaust heat, the main focus is on promoting useful chemical reactions (gas reforming) of COG that can only be performed at high temperatures. Is considered advantageous.

  Since the ascending pipe also needs to be opened and closed, usually two valves, the ascending pipe top lid and the dry main lid, are provided. The riser top lid is for burning the residual gas in the coke oven while being released into the atmosphere after the end of dry distillation, and is sealed with water between the riser and the work. Alternatively, in order to prevent the top cover of the riser from sticking to the riser due to the deposit of deposits, it is also possible to use a structure that does not completely seal COG by providing a gap in advance between the riser and the lid. It has been. The dry main lid is a pipe lid connecting the ascending pipe and the dry main, which is also sealed with water when the pipe is closed. As described above, the valve that can contact the wet COG in the prior art has a structure that is maintained at a low temperature or is not completely sealed.

JP 2004-107466 A Japanese Utility Model Publication No. 62-39077 Japanese Utility Model Publication No. 58-7847

  In order to use the sensible heat of COG in the wet COG state, a valve that can open and close the conduit for controlling the flow of the wet COG in the high temperature state in the conduit system is indispensable. However, is it impossible to completely seal the wet COG with the valve (lid) of the prior art, or whether the dust contained in the wet COG bites into the valve seat and the valve box and hinders the opening / closing and sealing performance of the valve? There are only uncertain or difficult to realize such as low temperature of wet COG, or the need to remove tar and solid carbon that adheres to the inner surface of the valve after frequent operation (coal dry distillation) I did not.

  Therefore, in the present invention, contamination and corrosion of the valve seat and valve box due to gas components become a problem, and for gases that must be maintained at a high temperature, for example, wet COG from room temperature to about 900 ° C. An object of the present invention is to provide a high-temperature furnace gas gate valve that can control long-term flow in a pipeline.

As a result of the inventors' research, the following solutions have been invented.
The first invention comprises an upper lid for switching the system between a sealed state and an open state;
A sealing material introduction pipe for guiding the sealing material from outside the system into the valve box;
The inside of the valve box is placed in a heating furnace having a temperature ranging from room temperature to 900 ° C., connected to the gas pipe from the upstream and the gas pipe to the downstream, and the inside of the valve box is sealed using the sealing material introduced into the valve box. A valve box provided with a threshold plate for separating the upstream space and the downstream space;
A sealing material discharge pipe for discharging the sealing material in the valve box out of the system;
A lower lid for switching between a state in which the sealing material inside the valve is discharged out of the system and a state in which the sealing material does not flow out of the system;
Are high-temperature furnace gate valves that are connected in order from above to below,
The valve box and the squeezing plate are configured so that the radius of curvature of the streamline of the gas flowing into the valve box through the gas pipe from the upstream is ½ or less of the maximum width of the valve box ,
A high temperature furnace gate valve characterized in that the sealing material is a substance mainly composed of metallic gallium .

The sealing material may be a granule mainly composed of one or a combination of two or more of aluminum oxide, zirconium oxide, titanium oxide, silicon nitride, and silicon carbide .

The second invention comprises an upper lid for switching the system between a sealed state and an open state;
A sealing material introduction pipe for guiding the sealing material from outside the system into the valve box;
The inside of the valve box is placed in a heating furnace having a temperature ranging from room temperature to 900 ° C., connected to the gas pipe from the upstream and the gas pipe to the downstream, and the inside of the valve box is sealed using the sealing material introduced into the valve box. A valve box provided with a threshold plate for separating the upstream space and the downstream space;
A sealing material discharge pipe for discharging the sealing material in the valve box out of the system;
A lower lid for switching between a state in which the sealing material inside the valve is discharged out of the system and a state in which the sealing material does not flow out of the system;
Are high-temperature furnace gate valves that are connected in order from above to below,
The valve box and the squeezing plate are configured so that the radius of curvature of the streamline of the gas flowing into the valve box through the gas pipe from the upstream is ½ or less of the maximum width of the valve box,
The sealing material is aluminum oxide, zirconium oxide, titanium oxide, silicon nitride, among the silicon carbide, the high temperature furnace lest you characterized in that one or more combinations where at granules mainly It is a gate valve.

The features of the present invention will be described.
The first feature is that a valve in a wide range required for the present invention is used by using a granular material whose physical properties do not change greatly in a temperature range from room temperature to a high temperature of about 900 ° C. as a sealing material for a gate valve. This is the point of securing the sealing property. On the other hand, in the case of the sealing method of a prior art, for example, a water seal valve, since water cannot be maintained as a liquid phase at high temperature, this cannot be applied.

  The second feature is as follows. In the gate valve, it is common to use a combination of different materials for the gate valve parts depending on the required function. When such a gate valve is used in a wide temperature range, a difference in thermal expansion occurs between the parts. Therefore, in the contact between the parts, for example, in the contact between the valve seat and the valve box, it is said in machining. It is difficult to keep the fit in the same state over a wide temperature range. In addition, when the valve is used at a high temperature of 900 ° C., it is inevitable that the material will be deformed by creep in the long term. Therefore, even if the operating temperature is constant, the same fitting is performed over a long period of time. It is also difficult to maintain a match. Since the gate valve of the prior art has a structure in which the working fluid is sealed by tightening the valve box to the valve seat, if the fitting of the valve changes, a gap is generated between the valve box and the valve seat, and sealing is not performed. There is a problem that it becomes complete, or conversely, the contact force between the valve casing and the valve seat becomes excessive and the valve casing cannot be moved. On the other hand, in the present invention, since the movable part does not exist in the valve box and fluid or particles that can be freely deformed are used as the sealing material, the above-described problems can be avoided.

  The third feature is that, in the present invention, since a relatively large amount of granular sealing material is used, coking and tar condensing and solidification of the material, which cannot be avoided with the material in contact with the wet COG, and in the gas It is difficult to be adversely affected by the adhesion of the dust contained in the dust, and the dust flow contained in the wet COG is actively collected and fixed in the sealing material by devising the flow path structure in the valve box Therefore, the effect of cleaning the gas can be exhibited with respect to the device on the downstream side of the valve. Further, in the apparatus of the present invention, since the sealing material is exchanged every time the valve is opened and closed, the influence of deterioration of the sealing performance and workability due to the deterioration of the sealing material is small.

  The fourth feature is that, in the present invention, most of the structure of the valve is disposed in the heating furnace, so that the temperature difference between the parts of the valve can be reduced. In a valve that circulates high-temperature gas in the prior art, it is aimed to ensure the strength and workability of the valve by keeping the inside, which is the contact area with the high-temperature gas, at a high temperature and keeping the outside of the valve at a low temperature. I came. Under such a design premise, when the heating device is not provided in the valve, the hot gas passing through the valve is cooled by the valve, so that, for example, precipitation of tar on the inner surface of the valve is unavoidable when circulating wet COG. There is. A method of avoiding heat removal from the hot gas passing through the valve by providing a heating device inside the valve is also conceivable, but in this case, the temperature difference between the inside and outside of the valve is large. It is difficult to control the temperature uniformly. In addition, these prior art methods provide a large temperature difference between the valve components, so that when the valve is used at a high temperature of 900 ° C., a large thermal stress is generated and the life of the valve is significantly reduced. Problems also arise. In the present invention, the temperature of the entire valve can be kept uniform and constant by disposing the valve in a heating furnace maintained at substantially the same temperature as the hot gas passing through the valve. You can avoid problems with

  As a fifth feature, the apparatus of the present invention has a simple valve box structure and has a valve opening (upper cover and lower cover) provided outside the high-temperature furnace. Even in this case, the function of the valve can be easily restored by inserting a jig into the valve box through the opening. In the case of the prior art gate valve, when the valve box is blocked, it is necessary to remove the valve from the system and disassemble it.

  According to the present invention, various gas reforming techniques using sensible heat of wet COG can be applied.

It is a schematic diagram of the structure of the valve in embodiment of this invention. It is a mimetic diagram in the state where a valve was closed in an embodiment of the present invention. It is a schematic diagram of the state which opened the valve in embodiment of this invention. It is a schematic diagram of the streamline of gas and the locus | trajectory of particle | grains in embodiment of this invention.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

(Valve structure)
The structure of the gate valve according to the embodiment of the present invention will be described with reference to FIG. The valve box 1 is installed in the high-temperature furnace 8 and is maintained at a high temperature of, for example, 800 ° C. or higher, thereby preventing condensation of tar in wet COG passing through the valve box 1. An upper gas pipe 9 and a downstream gas pipe 10 for circulating the working gas are connected to the upper portion of the valve box 1. A threshold plate 6 that is a cylinder having an opening in the valve box 1 is connected to the inside of the valve box 1. A sealing material introduction pipe 2 is connected to the valve box 1 above the valve box 1, and the sealing material can be introduced into the valve box 1 from outside the system through the pipe 2. An upper lid 4 is connected to the upper end of the sealing material introduction pipe 2 and is opened when the sealing material is introduced into the valve box 1 or when the sealing material is blocked in the valve box 1. When the jig for performing the operation is inserted into the valve box, the upper lid 4 is opened, and otherwise the upper lid 4 is closed to ensure the airtightness inside the valve box 1. A sealing material outflow pipe 3 is connected to the valve box 1 below the valve box 1, and a part or all of the sealing material in the valve box 1 and the valve box 1 are collected through the pipe 3. The fine particles in the working gas are discharged out of the system. A lower lid 5 is connected to the lower end of the sealing material outflow pipe 3 so that the sealing material is blocked when the sealing material is discharged from the valve box 1 or within the valve box 1 or the sealing material outflow pipe 3. The lower lid 5 is opened when, for example, a jig for performing an opening operation is inserted into the valve box 1 when the valve has occurred, and the lower lid 5 is closed and the valve box 1 is closed otherwise. Ensure internal airtightness. As the structure of the upper lid 4 and the lower lid 5, a commercially available opening / closing lid can be used, and the opening / closing operation can be performed manually. In order to adjust the fluidity of the sealing material in a state where the furnace temperature is low, a heater 12 may be appropriately provided around the valve box 1. Supply of the sealing material to the valve box 1 may be performed manually using a scoop or the like, or a sealing material supply device 7 such as a commercially available hopper or feeder may be used.

  As a material constituting the valve, a heat-resistant stainless steel such as SUS310, a heat-resistant nickel alloy such as Hastelloy, or a heat-resistant ceramic can be applied to a material disposed in a high-temperature furnace. Moreover, regarding the components arranged outside the furnace, there is no particular limitation as long as the strength can be maintained. For example, ordinary steel can be used. Moreover, as a sealing material for an upper lid or a lower lid, a commercially available resin sealing material can be used on the assumption that this part is maintained at a temperature of about 200 ° C. or less.

  The dimensions of the valve box 1 are not particularly limited, but the curvature of the gas flow so as to efficiently separate the particles of several tens to several hundreds of μm, which mainly form the fine particles contained in the wet COG, from the working gas. From the viewpoint of adjusting the pressure, the maximum width of the valve box 1 is preferably in the range of 50 mm to 3000 mm.

  The upper end part or the lower end part of the sealing material introduction pipe 2 and the sealing material outflow pipe 3 can be arranged outside the high temperature furnace. By doing in this way, the temperature of the upper lid 4 and the lower lid 5 connected to the sealing material introduction pipe 2 and the sealing material outflow pipe 3 can be kept sufficiently lower than in the high temperature furnace, and the lid opening / closing operation In addition, the introduction / outflow operation of the sealing material can be easily performed.

(Valve open / close operation)
The valve closing operation will be described with reference to FIG. 2 showing the valve closed state. The upper lid 4 is opened with the lower lid 5 closed, and the sealing material 11 is supplied into the valve box 1 from here. The supply amount of the sealing material 11 is equal to or more than the amount in which the lower end of the threshold plate 6 is entirely buried in the sealing material 11 and the surface of the sealing material 11 does not reach the height of the downstream gas pipe 10. Set as follows. In setting the sealing material height, the height can be appropriately adjusted by visual observation through the sealing material introduction tube 2. In the state of FIG. 2, the space on the upstream gas pipe 9 side and the space on the downstream gas pipe 10 side are separated by the threshold plate 6 and the sealing material 11 in the valve box. Can be suppressed.

  Next, the valve opening operation will be described with reference to FIG. The lower lid 5 is opened with the upper lid 4 closed, and a predetermined amount of the sealing material 11 in the valve box 1 is discharged therefrom. The discharge amount of the sealing material 11 is not more than the height at which at least a part of the lower end of the threshold plate 6 is exposed from the sealing material 11 on the surface of the sealing material 11 in the valve box 1, and the sealing material flows out. In the pipe 3, it adjusts suitably so that it may be the height more than the site | part located in a high temperature furnace. In setting the sealing material height, the height can be appropriately adjusted by visual observation through the sealing material introduction tube 2. In the state of FIG. 3, since the space on the upstream gas pipe 9 side and the space on the downstream gas pipe 10 side are connected in the valve box 1, the working gas is circulated from the upstream gas pipe 9 to the downstream gas pipe 10. Can do. The reason why the sealing material remains in the sealing material outflow pipe 3 is to maintain the temperature inside the valve box 1 at a high temperature by causing the sealing material 11 to act as a heat insulating material.

(Flow in the valve box)
The flow of the working gas in the valve box 1 and the fine particles floating in the gas will be described with reference to FIG. In the open state of the valve, the typical flow line 13 of the working gas flowing in from the upstream gas pipe 9 first swirls along the inner wall of the valve box according to the flow path structure formed by the valve box 1 and the threshold plate 6. Then, after going around the lower end of the threshold plate 6, it rises and finally flows out from the downstream gas pipe 10. At this time, an arbitrary streamline of the working gas has a radius of curvature of the valve box 1 (this length is about the same as 1/2 of the maximum width of the valve box 1 and, of course, , Never greater than ½ of the maximum width). In this way, in the valve box 1, there is a portion having a small radius of curvature in any working gas stream line. Therefore, the fine particles contained in the working gas at this portion cannot follow the gas flow and slip. Further, some or all of the fine particles generated and slipped collide with the inner wall of the valve box 1 and decelerate, and finally are supplemented by the sealing material 11 existing below the valve box 1 to be working gas. It is removed from the inside (this state corresponds to the locus 14 of the fine particles). As a result, it is possible to reduce the influence of dust in the gas, which is a big problem when applying the gate valve of the prior art to wet COG.

(Encapsulant)
As the sealing material 11, a liquid metal mainly composed of metallic gallium can be used. Since the melting point of metallic gallium is 29 ° C. and the boiling point is 2000 ° C. or higher, the sealing gas temperature is maintained at the melting point or higher by using the heater 12 or the like, so that the working gas temperature is sealed within the range from room temperature to 900 ° C. The stopper can maintain a liquid phase. Since the vapor pressure of metallic gallium at 900 ° C. is as low as about 0.1 Pa or less, there are a number of problems that may occur due to evaporation of the sealing material, such as solidification of the sealing material 11 in the downstream equipment of the valve. Kimono generation can be avoided.

  Here, the “main body” refers to a liquid metal in which metal gallium occupies 50 mass% or more, and the properties of the above metal gallium, in particular, a melting point at a low temperature of about room temperature or less, and the operation of wet COG. Trace amounts of impurities or additives can be contained in the metal gallium without greatly impairing the advantage of having a boiling point that is sufficiently higher than the temperature. For example, the liquid metal containing 68.5% by mass of metal gallium, 21.5% by mass of indium and 10% by mass of tin occupies most of the components, and has a melting point of −19 ° C. and a boiling point of 1300 ° C. or higher. Therefore, it cannot be said that the properties of metallic gallium are significantly impaired. Therefore, it is included in the liquid metal mainly composed of metallic gallium as referred to in the present invention. In addition, a material such as recycled gallium, which can contain impurities in the order of about 1% by mass, also satisfies the condition that the melting point is a low temperature of about room temperature or lower and the boiling point is sufficiently higher than the operating temperature of wet COG. In the present invention, it is included in the liquid metal mainly composed of metal gallium.

  Further, as the sealing material 11, a granule mainly composed of one or a combination of two or more of aluminum oxide, zirconium oxide, titanium oxide, silicon nitride, and silicon carbide can be used. These materials are easily obtained industrially, are stable in the temperature range from room temperature to 900 ° C., have low reactivity with wet COG, and further have low sinterability in this temperature range. It is preferable because the fluidity is hardly impaired. In the case of other substances, for example, silica sand, transformation occurs in this temperature range, so that the particles are easily collapsed and are not suitable as the sealing material 11. Further, when soda glass particles are used, softening and sintering can occur in this temperature range, and the fluidity of the particles cannot be ensured and the valve box is blocked, which is not suitable as the sealing material 11.

  Here, the main body means that the above-mentioned particles occupy 50% by mass or more, and the properties of the above-mentioned particles, in particular, stable in the temperature range from room temperature to 900 ° C., and the reactivity with wet COG. In addition, a small amount of impurities or additives are contained in the above-mentioned granules as particles or as components of individual particles of the above-mentioned granules within a range that does not significantly impair the advantage of low sinterability at this temperature range. obtain. For example, boron nitride particles can be added to the particles in a range of, for example, about 5% by mass or less. Since boron nitride has high solid lubricity at high temperatures, an effect of improving the fluidity of the particles can be expected by adding a small amount to the above particles. However, since boron nitride grains have low mechanical strength and easily disintegrate, it is difficult to maintain the desirable grain range shown below for a long period of time, so there is a problem in adding a large amount. Moreover, it is not always necessary to use high-purity particles as the fluid particles, for example, particles containing silicon oxide and composed of particles having a mullite alumina-silica composition, Any silica content ratio range (for example, 30% by mass or less) that does not significantly impair the properties of the above-described granules can be applied.

  Moreover, when using a granule for the sealing material 11, the particle size of a granule can be 30 micrometers or more and 500 micrometers or less. When a particle larger than this range is used, the sealing performance of the valve by the sealing material 11 is significantly deteriorated, which is not preferable. When particles smaller than this range are used, the scattering of particles on the surface of the sealing material 11 remaining in the valve box 1 or the sealing material outflow pipe 3 due to the working gas flow when the valve is opened is remarkable. This is not preferable.

  As the sealing material 11, it is also possible to simultaneously apply the above-described liquid metal mainly composed of metallic gallium and the above-mentioned preferred particles. In addition, when using metal gallium and the said granule together, both are combined and it is 50 mass% or more. In this case, since the specific gravity of the granule is smaller, the granule floats on the liquid metal, suppresses the oxidation of the liquid metal on the surface of the liquid metal, and the granule functions as a heat insulating material. The effect of keeping the inside of the box 1 warm can be enhanced.

  The sealing material 11 discharged outside the system when the valve is opened is recovered, and the recovered soot is removed off-line by sieving or the like, and then the sealing material 11 can be reused.

  The sealing material is not limited to the types described above. For example, since high-purity tungsten oxide is a highly stable substance at high temperatures, if it can be produced in large quantities with a predetermined particle size, it can be applied to the sealing material of the present invention.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Valve box 2 ... Sealing material introduction pipe 3 ... Sealing material outflow pipe 4 ... Upper lid 5 ... Lower lid 6 ... Cutting plate 7 ... Sealing material supply apparatus 8 ... High-temperature furnace 9 ... Upstream gas pipe 10 ... Downstream gas pipe 11 ... Sealing material 12 ... Heater 13 ... Gas stream line 14 ... Particle trajectory 15 ...・ Gas streamline radius of curvature

Claims (3)

An upper lid for switching the system between a sealed state and an open state;
A sealing material introduction pipe for guiding the sealing material from outside the system into the valve box;
The inside of the valve box is placed in a heating furnace having a temperature ranging from room temperature to 900 ° C., connected to the gas pipe from the upstream and the gas pipe to the downstream, and the inside of the valve box is sealed using the sealing material introduced into the valve box. A valve box provided with a threshold plate for separating the upstream space and the downstream space;
A sealing material discharge pipe for discharging the sealing material in the valve box out of the system;
A lower lid for switching between a state in which the sealing material inside the valve is discharged out of the system and a state in which the sealing material does not flow out of the system;
Are high-temperature furnace gate valves that are connected in order from above to below,
The valve box and the threshold plate are configured so that the radius of curvature of the streamline of the gas flowing into the valve box through the gas pipe from the upstream is equal to or less than ½ of the maximum width of the valve box ,
A gate valve for a high temperature furnace, wherein the sealing material is a substance mainly composed of metallic gallium . The sealing material is aluminum oxide, zirconium oxide, titanium oxide, silicon nitride, among the silicon carbide, according to claim 1, characterized in that the granules consisting mainly of one or more of the combinations Gate valve for high temperature furnace. An upper lid for switching the system between a sealed state and an open state;
A sealing material introduction pipe for guiding the sealing material from outside the system into the valve box;
The inside of the valve box is placed in a heating furnace having a temperature ranging from room temperature to 900 ° C., connected to the gas pipe from the upstream and the gas pipe to the downstream, and the inside of the valve box is sealed using the sealing material introduced into the valve box. A valve box provided with a threshold plate for separating the upstream space and the downstream space;
A sealing material discharge pipe for discharging the sealing material in the valve box out of the system;
A lower lid for switching between a state in which the sealing material inside the valve is discharged out of the system and a state in which the sealing material does not flow out of the system;
Are high-temperature furnace gate valves that are connected in order from above to below,
The valve box and the threshold plate are configured so that the radius of curvature of the streamline of the gas flowing into the valve box through the gas pipe from the upstream is equal to or less than ½ of the maximum width of the valve box,
A gate valve for a high-temperature furnace, wherein the sealing material is a granule mainly composed of one or a combination of two or more of aluminum oxide, zirconium oxide, titanium oxide, silicon nitride, and silicon carbide. .