JPS5945603B2 - Method for producing homogeneous inorganic mass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a homogeneous rod-shaped molten silica ingot, and more specifically, a method for producing a homogeneous fused silica ingot of various sizes and shapes using a gas heating furnace. Pertaining to law.

Molten silica ingots are increasingly in demand as refractory materials for continuous casting immersion nozzles and coke ovens, and are now industrially mass-produced by melting silicon dioxide raw materials in electric furnaces, gas heating furnaces, and the like.

However, when manufacturing using an electric furnace, particularly by induction heating, the equipment becomes large and a large amount of expensive electrical energy is used, which poses problems in terms of economy.

In addition, gas heating furnaces have no equipment restrictions and can achieve high temperatures even with small ones. Voids remain uniformly, striae and granular structures are observed even in areas without voids, and it is difficult to obtain fused silica in the form of a uniform molten lump.

When used as a raw material for ceramics, it is crushed, mixed with particle size,
This is not a problem because the molded body is obtained by molding and firing, but when the molten body is directly molded into industrial products by machining or thermal processing, large voids remain and cracks occur due to internal strain, making it unusable. occurs.

For this reason, methods for producing homogeneous molten perilla using a gas heating furnace have been researched for some time, and one example of this is the
A manufacturing method described in Japanese Patent No. 4211 has been proposed.

However, this manufacturing method has the disadvantage that it is difficult to produce large and irregular shapes, and it takes a very long time to manufacture.

That is, this manufacturing method is a method of manufacturing fused silica by melting a powdered quartz raw material at the focal point of a burner and stacking the molten layers one after another.

However, in this method, only the focal point of the burner is melted, and the point melting is in a small area, so it takes time to melt the raw material, making it unsuitable for mass production.

Further, in this manufacturing method, the molten layer is used as a rotating body, and a burner is focused on an eccentric portion of the rotating molten layer to form a silica melt of a required size.

Even in this case, the dimensions of the fused silica are limited by the distance between the central axis of the rotating molten layer and the focus of the burner, so a molten body with large dimensions cannot be obtained.

The present invention aims to solve the above-mentioned drawbacks, and particularly proposes a method that can continuously and economically produce a homogeneous molten silica ingot when producing rod-shaped fused silica by melting raw materials in a gas heating furnace. do.

The method of the present invention will be explained in detail below.

First, in FIG. 1, reference numeral 1 indicates a gas heating furnace, and a melting chamber 7 is formed inside the heating furnace 1, and a through hole 2 is formed in the ceiling portion of the melting chamber 7.

A multi-tube burner 3 is provided in line with this through hole 2, and this burner 3 supplies hydrogen and oxygen as well as a raw material for silicon dioxide.

That is, as shown in FIG. 2, the burner 3 is composed of a central tube 4 and two annular tubes 5 and 6 surrounding it, and an inner annular tube 5 and an outer annular tube 6 are arranged concentrically around the central tube 4. do.

The diameter from this central cylinder 4 is 0.1 to 1. Silicon oxide raw material powder having a degree of OmmffN is continuously supplied into the melting chamber 7 of the heating furnace, and is spread so as to be uniformly dispersed on the flat melting surface 8a of the melt 8 as described later.

Further, hydrogen is supplied as a fuel from the inner annular pipe 5, and oxygen is further supplied from the outer annular pipe 6, and the hydrogen and oxygen are diffused and catalyzed in the entire area of the melting chamber 7, and at this time, the side wall of the melting chamber 7 The entire area of the melting chamber 7 is heated and maintained at a high temperature of 1800 to 2300° C. by controlling the amount of exhaust from a pair of exhaust ports 9a and 9b symmetrically provided in the melting chamber 7, for example, by a damper or the like.

Furthermore, when dispersing the raw material powder supplied from the tip of the center tube 4, a pyramid-shaped or conical dispersion tip 10 is attached to the spout at the tip of the center tube 4 of the burner, as shown in FIG. The area around it is opened, and the raw material powder is spread and dispersed by the dispersion chip 10.

When supplied in this way, the raw material powder flows into the melt 8 in the melting chamber 7.
The raw material is continuously supplied in a uniformly dispersed manner to the melting surface 8a, and as soon as the raw material comes into contact with this melting surface, it is melted.

Furthermore, during melting, the level of the melting surface 8a is maintained at a constant level in order to keep the porosity of the melt 8 below a predetermined value.

In addition, the particle size of the raw material powder should be about 0.1 to 1.0 mm because if the particle size is smaller than this, it will easily scatter outside the heating furnace.
This is because when it is more than Omm, sequential contact cannot be made due to the contact of the melting surface 8a.

As described above, raw material powder is continuously supplied and melted into chamber 7.
melts at the melting surface 8a over the entire area, while
The molten material 8 is lowered sequentially and continuously while the level of the molten surface 8a is kept constant, and during this descent, the molten material 8 is squeezed from the outer periphery, and the molten material 8 is cooled from the outer periphery only by this squeezed cooling part 8b. do.

When cooled in this way, the melt 8 is cooled only when the outer periphery is in contact with the throttle cooling part 8b, and the volume of the melt 80 due to this cooling hardly changes, and the molten state in the melting chamber 7 is changed. Even if there is some change, the level of the melt surface 8a is kept constant and a homogeneous molten ingot is obtained.Also, since the contact area of the throttle cooling part 8b used for cooling is small and local, the molten ingot is It can be easily taken out without sticking to the heating furnace or the like.

To explain in more detail, if the molten material 8 is cooled by making all of the side walls of the discharge passage 1a contact with each other as a cooling part without locally constricting the molten material 8, the cooling effect during descent becomes thicker (by increasing the volume, the molten surface 8a is cooled). The viscosity of fused silica increases rapidly as the temperature decreases, and the molten material 8 sticks to the discharge passage 1a, making it difficult to discharge.

In other words, if there is no throttle cooling section and the entire wall surface of the discharge passage is used as a cooling section, even if the cross-sectional area of the melting chamber and the discharge passage are the same, the amount of charge, the combustion state in the furnace, and the descending speed of the molten material will vary. It is difficult to obtain a homogeneous molten body because the molten surface changes easily due to fluctuations, and the molten state changes.

Furthermore, when the molten material 8 is squeezed and cooled from the outer periphery as it descends, as in the method of the present invention, the periphery of the molten material 8 is completely sealed in the squeezed cooling portion, and the temperature inside the melting chamber 7 is easily reduced. Can be held high.

In addition, in the case of throttle cooling, the melt 8 can be maintained at a temperature higher than the fixing temperature in the throttle cooling section, the external shape of the melt does not change as described above, and since the cross section of the throttle cooling section is smaller than the melting chamber, from this surface Also, even if the amount of charge, the combustion state in the furnace, and the rate of descent of the melt vary somewhat, the variation in the surface level 8a of the melt 80 is extremely small, and a homogeneous ingot can be produced.

Further, in the case of cooling by throttling as described above, as shown in FIG. 1, a protrusion 11 is made to protrude into the discharge passage 1a, and a throttling cooling section 8 is provided there.

It is preferable that the protrusion 11 is made of a refractory and wear-resistant material, and is configured to be able to be inserted into and removed from the furnace wall or replaced.

Note that when the silicon dioxide raw material is melted in a gas heating furnace using a burner or the like, a considerably high temperature is required, and this high temperature is usually only obtained at or near the focal point of the burner.

In this regard, in the method of the present invention, the periphery of the melt 8 descending through the gas heating furnace is completely sealed in the discharge passage, and the melting surface 8a where the raw material powder is melted is completely sealed in the melting chamber 7. Therefore, if the temperature inside the melting chamber 7 is maintained at 1800 to 2300°C due to the combustion of hydrogen and oxygen, the raw material powder can be quickly melted by simply scattering it evenly over the entire melting surface 8a, and large molten ingots can be formed. Easy to manufacture.

Next, examples will be described.

First, a gas heating furnace 1 as shown in Fig. 1 is constructed using stabilized zirconia bricks, and in this heating furnace, a convex step with a cross-sectional shape of 240 x 340 mm is formed to form a protrusion 11, and a cooling A cooling section made of gold is provided, and the melting chamber 7
The cross-sectional shape was 360×460.

In addition, a burner as shown in Figure 2 is set at the top of this heating furnace, and hydrogen gas is fed from this burner at a rate of 4 ON m/hour and oxygen gas is 2 ON m''/hour for combustion, and the temperature inside the furnace is was maintained at 1950-2050°C.

Next, Korean silica stone having a grain size of 1 to 0.1 mm was thrown from the central cylinder 4 of the burner at a rate of 20 kg/hour.

At this time, the Korean silica was melted so that the melting surface 8a was maintained at a position 400 mm from the tip of the burner and 150 mm upward from the protrusion 11, and the cross-sectional dimension was 33 mm.
0 mm x 230 mm fused silica prismatic ingot from 12~
It was ramped down at a rate of 13 cfIL/hr.

When the true porosity of the ingot obtained through the above operations was determined, it was 3.0 to 5.5% and was sufficiently homogeneous.

In addition, plates were actually cut out from the molten ingot and molded by welding, but there were no problems and the product could be used for purposes such as heat-resistant containers.

In addition, a particle size of 1 mm was obtained using the same method as above.
A prismatic ingot was produced by melting 1J of Korean silica and Korean silica with a grain size of 0.1 mm or less.

As a result, some granular structure was observed in the ingots obtained from particles with a particle size of 1 mm or more, but there were no major problems.

Furthermore, particles with a particle size Q of 1 mm or less tend to scatter if the exhaust port is incorrectly adjusted, and at the same time, there remains a slight problem in uniform dispersion within the heating furnace.

Further, in the above case, when the temperature inside the furnace was lowered to 1800° C. or lower, the melting temperature became slightly uneven, and the descent of the molten ingot tended to be uneven.

In addition, when the temperature inside the furnace was raised to over 2300℃,
A phenomenon occurred in which the furnace material melted and was mixed into the molten material.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an example of a gas heating furnace used in carrying out the method of the present invention, and FIG. 2 is a sectional view of a burner of the gas heating furnace shown in FIG. Code 1...Gas heating furnace, 2...Through hole, 3...Burner, 4...Center cylinder, 5,
6... Annular tube, 7... Melting chamber, 8...
...Melted body, 8a...Surface, 8b...
... Throttle cooling section, 9a, 9b... Exhaust port, 10
...Distributed chip, 11... Protrusion.

Claims (1)

[Claims] 1. A multi-tube burner is installed in the upper center of a gas heating furnace which is equipped with a raw material melting chamber inside and a pair of exhaust ports are symmetrically formed in the side wall. ~1 mm of silicon dioxide raw material is continuously fed so as to be uniformly distributed over the entire flat melting surface of the melt in the melting chamber, and the silicon dioxide raw material is melted on this melting surface while surrounding the central cylinder. Hydrogen gas is supplied from the inner annular tube, and oxygen is supplied from the outer annular tube surrounding the inner annular tube to the melting chamber for combustion, and the exhaust from each of the exhaust ports is adjusted to bring the temperature of the melting chamber to 1800.
The temperature is maintained at ~2300°C, and the solid-gas molten material is discharged while being continuously lowered from the bottom of the heating furnace.Moreover, at the time of discharge from the bottom of the furnace, only the constricted cooling part of the bottom of the furnace is placed on the outer periphery of the molten material. The outer periphery of the molten material is solidified by contacting and cooling it, and then
A method for producing a homogeneous rod-shaped fused silica ingot characterized by air cooling the outer periphery.