JP6722575B2 - melting furnace - Google Patents

Description

TECHNICAL FIELD The present invention relates to a melting furnace, and more particularly to improvement of a melting furnace for melting raw material powder in a crucible.

Some medical or optical glasses require certain qualities such as heat resistance and chemical stability. Such glass is obtained by melting powder as a raw material by heating and then quenching and crushing the melt. The raw material powder is heated and melted, for example, using a crucible type melting furnace.

This type of melting furnace includes a batch type and a continuous type, and in the case of a continuous type melting furnace, the quality of the glass product largely changes depending on the residence time of the melt in the crucible. For example, when the melt is retained, a desired composition can be formed by evaporating a part of the melt components. Therefore, the predetermined quality cannot be obtained even if the residence time of the melt is too long or too short.

In a continuous melting furnace, the residence time of the melt is determined by the amount of the raw material powder charged into the crucible per unit time, the crucible size and the height of the overflow pipe. The overflow pipe is a pipe for discharging the melt that extends vertically through the bottom plate of the crucible. By discharging the melt that remains in the crucible through the upper pipe mouth, the overflow pipe Limit the rise of. For example, the amount of raw material input is determined from the amount of production per day, and the height of the overflow pipe is determined from the size of the crucible and the residence time of the melt.

The appropriate residence time of the melt depends on the melt components and the melting furnace. For this reason, in the conventional melting furnace, a small test furnace is used to estimate the appropriate residence time by trial and error and determine the height of the overflow pipe. However, since the size of the crucible differs greatly between the test furnace and the actual production furnace, even if the overflow tube is installed as designed, the desired glass product is often not obtained, resulting in poor production efficiency. There was a problem.

Further, since the overflow pipe is installed on the bottom plate of the crucible, there is a problem that the residence time of the melt cannot be changed without changing the amount of raw material charged and the size of the crucible. For example, if the input amount of the raw material is reduced, the residence time can be lengthened, but the production amount of the glass product is reduced. On the other hand, if the input amount of the raw material is increased, the residence time can be shortened, but the energy consumption amount during heating and melting increases, and the production becomes excessive.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a melting furnace that can improve the production efficiency of glass products. In particular, it is an object to provide a melting furnace that can obtain a desired glass product without using a test furnace. Moreover, it aims at providing the melting furnace which can adjust the residence time of a melt, without interrupting a melting process.

The melting furnace according to the first aspect of the present invention comprises a crucible for melting powder of a raw material, a heating means for heating the powder charged in the crucible, and a bottom plate of the crucible penetrating through the crucible. And a liquid level adjusting pipe that restricts the rise of the liquid level beyond the opening by discharging the melt retained in the crucible through the opening provided in the pipe wall. The liquid level adjusting tube has a bellows-shaped portion that can expand and contract in the tube axis direction, and the bellows-shaped portion is arranged below the opening.

According to this structure, the upper limit of the liquid level height is changed by expanding and contracting the bellows-shaped portion of the liquid level adjusting tube in the tube axis direction, so that the residence time of the melt can be controlled. In particular, the upper limit of the liquid level can be easily changed depending on the melt component and the glass product. Therefore, the desired glass product can be obtained without using a test furnace. Further, the residence time of the melt can be adjusted without changing the amount of raw material charged and the size of the crucible.

In addition to the above configuration, the melting furnace according to the second aspect of the present invention further includes a heat insulating lid facing the upper opening of the crucible, and the liquid level adjusting pipe penetrates the heat insulating lid so as to be vertically movable. Is configured as follows.

With such a configuration, the bellows-shaped portion can be expanded and contracted by moving a portion of the liquid level adjusting tube above the heat insulating lid up and down. In particular, the bellows-shaped portion can be expanded and contracted in a state where the heat insulating lid is arranged on the crucible. Therefore, the residence time of the melt can be adjusted without interrupting the dissolution process.

The melting furnace according to the third aspect of the present invention is configured to further include, in addition to the above configuration, a reinforcing ceramic tube arranged in the liquid level adjusting tube above the opening. According to such a configuration, the strength is secured above the opening, so that it is possible to prevent damage to the liquid level adjusting pipe when the upper end of the liquid level adjusting pipe is moved up and down.

In the melting furnace according to the fourth aspect of the present invention, in addition to the above-mentioned configuration, the liquid level adjusting pipe is arranged at a small diameter portion below the bottom plate of the crucible, and above the bottom plate. The large-diameter portion has a larger diameter than the small-diameter portion, and the bellows-shaped portion and the opening are formed in the large-diameter portion.

According to such a configuration, the melt that exceeds the outflow amount to the small diameter portion is stored in the large diameter portion. Therefore, even if there is a temporal variation in the amount of melt flowing into the liquid level adjusting tube through the opening due to the variation in the amount of raw material input, it is possible to prevent the melt flowing into the small diameter portion from being interrupted. can do.

In the melting furnace according to the fifth aspect of the present invention, in addition to the above configuration, the crucible includes a partition plate for partitioning the first melting chamber into which the powder is charged and the second melting chamber in which the melt is retained. The first melting chamber and the second melting chamber communicate with each other through an opening provided at the lower end of the partition plate, and the liquid level adjusting pipe is arranged in the second melting chamber. Is composed of. According to such a configuration, the time during which the melt stays in the second melting chamber can be controlled by expanding and contracting the bellows-shaped portion.

In addition to the above configuration, the melting furnace according to the sixth aspect of the present invention is configured such that the crucible and the liquid level adjusting tube are both made of platinum. With such a configuration, it is possible to secure the same level of heat resistance as the crucible for the liquid level adjusting tube having the bellows-shaped portion.

According to the present invention, by expanding and contracting the bellows-shaped portion of the liquid level adjusting pipe in the pipe axis direction, the upper limit of the liquid level changes, so that the liquid level can be adjusted depending on the melt component and the glass product. The upper limit can be easily changed and the desired glass product can be obtained without the use of a test furnace. Further, the bellows-shaped portion expands and contracts by moving a portion of the liquid level adjusting tube above the heat insulating lid up and down, so that the residence time of the melt can be adjusted without interrupting the melting process. Therefore, the production efficiency of the glass product can be improved.

1 is a system diagram showing a configuration example of a glass melting system 1 including a melting furnace 10 according to an embodiment of the present invention. It is sectional drawing which showed the structural example of the melting furnace 10 of FIG. 1, and shows the cut surface at the time of cutting the melting furnace 10 by an AA cutting line. It is sectional drawing which showed the structural example of the melting furnace 10 of FIG. 2, and shows the cut surface at the time of cutting the melting furnace 10 by a BB cutting line. It is explanatory drawing which showed typically an example of the operation|movement at the time of the melting process in the melting furnace 10 of FIG.

<Glass melting system 1>
FIG. 1 is a system diagram showing a configuration example of a glass melting system 1 including a melting furnace 10 according to an embodiment of the present invention. In the figure, (a) shows the front surface of the glass melting system 1, and (b) shows the right side surface of the glass melting system 1.

The glass melting system 1 is a device for melting a powder of a raw material by heating to obtain a desired glass production part, and is composed of a melting furnace 10, a raw material charging device 20, and a crushing device 30. The melting furnace 10 and the raw material charging device 20 are installed on the gantry 2.

The raw material powder is, for example, a raw material powder prepared so as to match a target glass composition, and the glass product of the glass melting system 1 is used for medical glass, optical glass, and the like. The raw material charging device 20 is a powder supply device for continuously supplying the raw material powder to the melting furnace 10. The raw material powder is supplied into the melting furnace 10 through a raw material supply pipe 21.

The melting furnace 10 is a continuous production furnace, and heats and melts the powder charged into the furnace through the raw material supply pipe 21, and discharges the melt retained for a predetermined time from the furnace bottom. The crushing device 30 is a device for rapidly cooling the melt discharged from the melting furnace 10 to vitrify it and crushing the glass product.

The melt discharged from the melting furnace 10 is rapidly cooled by contact with the rollers 31 by passing through the two sets of rollers 31, and is crushed by the stress from the rollers 31. The operation part 111 protruding from the upper surface of the melting furnace 10 is a part of a liquid level adjusting tube described later, and is used for adjusting the residence time of the melt.

<Smelting furnace 10>
FIG. 2 is a cross-sectional view showing a configuration example of the melting furnace 10 of FIG. FIG. 2 shows a cut surface when the melting furnace 10 is cut by the plane represented by the AA cutting line shown in FIG. FIG. 3 is a sectional view of the melting furnace 10 of FIG. FIG. 3 shows a cut surface when the melting furnace 10 is cut by the plane represented by the BB cutting line shown in FIG. 2 and 3, pipes for supplying atmospheric gas such as air to each part or discharging the atmospheric gas and pipes for supplying cooling water to each part are omitted. ..

The melting furnace 10 is an electric heating type melting furnace, and includes an exterior 10a, a liquid level adjusting tube 11, a nozzle heating heater 13, a crucible 14, a sheath crucible 15, a heating element 16, a heat insulating material 17, a partition plate 18, and a melt. It is constituted by the discharge pipe 19. The exterior 10a is a cylindrical housing, and houses the crucible 14, the sheath crucible 15, and the heat insulating material 17.

The crucible 14 is a platinum container for dissolving raw material powder, and has a bottomed cylindrical shape that opens upward. The crucible 14 has a partition plate 18 for partitioning the melting chamber 14c into which the powder is charged and the melting chamber 14d in which the melt is retained.

The partition plate 18 has an arcuate cutting surface when cut by a horizontal plane and is arranged so as to face the inner surface of the side wall of the crucible 14. The melting chamber 14c and the melting chamber 14d communicate with each other via an opening 18a provided at the lower end of the partition plate 18. The sheath crucible 15 is a protective container that houses the crucible 14 and protects the crucible 14, and is made of a refractory material.

The heat insulating material 17 is a cylindrical member that surrounds the crucible 14 and the sheath crucible 15. The sheath crucible 15 is installed on the bottom of the heat insulating material 17. Further, the canopy portion of the heat insulating material 17 is a heat insulating lid facing the upper opening 14 a of the crucible 14.

The heating element 16 is a heating means for heating the powder charged in the crucible 14 and is composed of an electric resistance type heater. The heating element 16 has a U-shape extending in the vertical direction and is arranged between the outer peripheral surface of the sheath crucible 15 and the inner peripheral surface of the heat insulating material 17. Further, a plurality of heating elements 16 are arranged along the outer peripheral surface of the sheath crucible 15 at substantially regular intervals in the circumferential direction.

A liquid level adjusting pipe 11 for adjusting the upper limit of the liquid level and a melt discharge pipe 19 for discharging the remaining melt are attached to the crucible 14. The liquid level adjusting pipe 11 is an overflow pipe that penetrates the bottom plate 14b of the crucible 14 and extends in the up-and-down direction, and discharges the melt retained in the crucible 14 through the opening 112 provided in the pipe wall. Limit the rise of the liquid level past the opening 112. The opening 112 is a through hole that penetrates the tube wall, and has, for example, a circular shape. A plurality of openings 112 are arranged in the circumferential direction at substantially regular intervals.

The liquid level adjusting pipe 11 is made of a platinum pipe having a circular cut surface when cut by a horizontal flat surface, and has an operating portion 111 projecting from the upper surface of the exterior 10a and a bellows-shaped portion that can expand and contract in the pipe axial direction. It has 113 and the discharge nozzle part 114 arrange|positioned below the bottom plate 14b. The operation portion 111, the bellows-shaped portion 113, and the discharge nozzle portion 114 are integrally formed.

The bellows-shaped portion 113 is a bellows portion for controlling the residence time of the melt by adjusting the height of the liquid surface from the bottom plate 14b, and the outer diameter and the inner diameter of the bellows portion 113 are predetermined according to the position in the pipe axis direction. It is formed by changing the pitch. The bellows-shaped portion 113 is arranged below the opening 112.

The liquid level adjustment pipe 11 can extend and contract the bellows-shaped portion 113 by vertically movably penetrating the canopy portion (heat insulating lid) of the heat insulating material 17 and the exterior 10a and moving the operation portion 111 up and down. In particular, the bellows-shaped portion 113 can be expanded and contracted with the heat insulating lid placed on the crucible 14. Therefore, the residence time of the melt can be adjusted without interrupting the dissolution process.

The discharge nozzle portion 114 penetrates the bottom portion of the sheath crucible 15 and the bottom portion of the heat insulating material 17, the lower end portion thereof projects from the lower surface of the exterior 10a, and the lower pipe mouth serves as an outlet 116 for flowing out the glass melt. .. The discharge nozzle portion 114 is a small-diameter portion having a smaller diameter than the portion of the liquid level adjusting tube 11 above the bottom plate 14b. On the other hand, a portion of the liquid level adjusting tube 11 above the bottom plate 14 b is a large diameter portion having a diameter larger than that of the discharge nozzle portion 114. The bellows-shaped portion 113 and the opening 112 are formed in this large diameter portion.

By adopting such a configuration, the melt that exceeds the outflow amount to the small diameter portion is stored in the large diameter portion. Therefore, even if there is a temporal variation in the amount of the melt flowing into the liquid level adjusting tube 11 through the opening 112 due to the variation in the amount of the raw material input, the melt flowing into the small diameter portion is interrupted. Can be prevented.

A ceramic tube 12 for reinforcement is arranged in the liquid level adjusting tube 11 above the opening 112. The ceramic tube 12 is made of, for example, aluminum oxide (alumina), traverses the upper opening 14 a of the crucible 14, penetrates the canopy portion of the heat insulating material 17 and the exterior 10 a, and reaches the operation portion 111. The bellows-shaped portion 113 can be stretched or contracted by moving the operation portion 111 upward or downward. Further, since the strength is secured above the opening 112, it is possible to prevent the liquid level adjusting tube 11 from being damaged when the operation unit 111 of the liquid level adjusting tube 11 is moved up and down.

The discharge nozzle portion 114 is provided with a nozzle heater 13 for heating the melt in the nozzle and a direct current conducting portion 115. The nozzle heater 13 is an electric resistance type heating element, and is arranged in the bottom portion of the heat insulating material 17 so as to surround the outer peripheral surface of the discharge nozzle portion 114. The direct-current-conducting portion 115 is a heating unit that directly causes an electric current to flow through a portion of the discharge nozzle portion 114 to generate heat, and is formed between the bottom portion of the heat insulating material 17 and the exterior 10a.

The melt discharge pipe 19 is a pipe whose upper pipe mouth is exposed from the bottom plate 14b of the crucible 14 and extends vertically through the bottom of the sheath crucible 15 and the bottom of the heat insulating material 17, and the lower end of which is the exterior 10a. The lower pipe mouth projects from the lower surface and serves as a discharge mouth 192 for discharging the residual glass. The melt discharge pipe 19 is made of a platinum pipe having a circular cut surface when cut along a horizontal plane.

The melt discharge pipe 19 is provided with a heater 190 for heating the melt in the pipe and a direct conduction part 191. The heater 190 is an electric resistance type heating element, and is arranged in the bottom portion of the heat insulating material 17 so as to surround the outer peripheral surface of the melt discharge pipe 19. The direct-current-carrying part 191 is a heating means for supplying an electric current directly to a part of the melt discharge pipe 19 to generate heat, and is formed between the bottom part of the heat insulating material 17 and the exterior 10 a.

The raw material supply pipe 21 extends vertically through the exterior 10a and the canopy portion of the heat insulating material 17 to the upper opening 14a of the crucible 14, and the lower pipe mouth thereof inputs raw material powder into the crucible 14. It has a mouth 22.

To illustrate the sizes of the crucible 14 and the liquid level adjusting tube 11, the crucible 14 has a diameter of about 200 mm and a volume of about 14 L. The bellows-shaped portion 113 has an approximately sinusoidal cut surface when cut along a plane parallel to the tube axis direction, and has an outer diameter of a peak portion of about 46 mm and an outer diameter of a valley portion of about 41 mm. Further, the thickness of the tube wall of the bellows-shaped portion 113 is approximately 0.5 mm and is substantially uniform. The pitch of the bellows is about 5 mm.

<Method of manufacturing bellows-shaped portion 113>
The bellows-shaped portion 113 is formed by, for example, producing a pipe having a predetermined wall thickness and drawing the pipe using an inner mold. For this reason, the bellows portion of the pipe has no joints such as welding, and strength and durability can be secured.

FIG. 4 is an explanatory view schematically showing an example of the operation during the melting process in the melting furnace 10 of FIG. The powder 3 charged into the melting chamber 14c of the crucible 14 is heated to a temperature of about 1500° C. to 1700° C. and melted. The glass melt 4 accumulated in the melting chamber 14c moves to the melting chamber 14d through a gap between the partition plate 18 and the bottom plate 14b of the crucible 14 and stays in the melting chamber 14d.

The glass melt 4 staying in the melting chamber 14d rises to the height of the opening 112 of the liquid level adjusting tube 11, flows into the tube of the liquid level adjusting tube 11 through the opening 112, and the bellows-shaped portion 113 and the discharge nozzle. It passes through the portion 114 and is discharged from the outlet 116. Since the liquid level adjusting tube 11 is arranged in the melting chamber 14d, the time during which the glass melt 4 stays in the melting chamber 14d can be controlled by expanding and contracting the bellows-shaped portion 113.

According to the present embodiment, the upper limit of the liquid surface height is changed by expanding and contracting the bellows-shaped portion 113 of the liquid surface adjusting tube 11 in the tube axis direction, so that the residence time of the glass melt 4 is controlled. You can In particular, the upper limit of the liquid level can be easily changed depending on the melt component and the glass product. Further, the residence time of the glass melt 4 can be adjusted without changing the amount of raw material charged and the size of the crucible 14.

In the present embodiment, an example of a small melting furnace in which the inside of the crucible 14 is partitioned by the partition plate 18 has been described, but the present invention does not limit the configuration of the crucible to this. For example, the present invention is also applicable to a melting furnace in which the melting chamber 14c and the melting chamber 14d are respectively formed in separate crucibles and are connected to each other by a pipe or the like.

DESCRIPTION OF SYMBOLS 1 Glass melting system 10 Melting furnace 11 Liquid level adjusting pipe 111 Operation part 112 Opening 113 Bellows-shaped part 114 Discharge nozzle part 115 Direct energizing part 13 Nozzle heating heater 14 Crucible 14a Upper opening 14b Bottom plate 14c, 14d Melting chamber 15 Sheath crucible 16 Heat generation Body 17 Heat insulating material 18 Partition plate 19 Melt discharge pipe 20 Raw material feeding device 21 Raw material supply pipe 30 Crushing device 31 Roller

Claims (6)

A crucible for melting the raw material powder,
Heating means for heating the powder charged in the crucible,
A liquid level that extends vertically through the bottom plate of the crucible and discharges the melt retained in the crucible through an opening provided in the tube wall to limit the rise of the liquid level beyond the opening. With adjusting tube,
The melting furnace, wherein the liquid level adjusting tube has a bellows-shaped portion that can expand and contract in the tube axis direction, and the bellows-shaped portion is arranged below the opening. Further comprising an insulating lid facing the upper opening of the crucible,
The melting furnace according to claim 1, wherein the liquid level adjusting pipe penetrates the heat insulating lid so as to be vertically movable. The melting furnace according to claim 2, further comprising a reinforcing ceramic tube arranged in the liquid level adjusting tube above the opening. The liquid level adjusting pipe is composed of a small diameter portion arranged below the bottom plate of the crucible and a large diameter portion arranged above the bottom plate and having a diameter larger than the small diameter portion, The melting furnace according to claim 1, wherein the bellows-shaped portion and the opening are formed in the large-diameter portion. The crucible has a partition plate for partitioning the first melting chamber into which the powder is charged and the second melting chamber in which the melt is retained, and through the opening provided at the lower end of the partition plate. The first melting chamber and the second melting chamber communicate with each other,
The melting furnace according to claim 1, wherein the liquid level adjusting tube is arranged in the second melting chamber. The melting furnace according to any one of claims 1 to 5, wherein both the crucible and the liquid level adjusting tube are made of platinum.

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