JPS633237B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resistance electric furnace, and particularly to the structure around its electrodes.

Conventionally, crushed slag stone made by slowly cooling slag by-product from blast furnaces in steel plants is remelted, and the composition and temperature are adjusted to produce molten slag with a predetermined composition and temperature. Rock wool is produced by fiberizing it using pressure. Recently, from the perspective of energy saving, molten slag from blast furnaces has been used directly, and its composition has been adjusted.
Techniques have also been developed to adjust the temperature to produce molten slag for fiberization. In these rock wool manufacturing processes, a resistance electric furnace is used to prepare molten slag for fiberization.

In a resistance type electric furnace, two or three electrodes are usually immersed in the material to be melted, and electricity is passed between each electrode and between the electrodes and the furnace wall or bottom, thereby melting and elevating the material with the resistance heat. An example of this is shown in FIG. In the figure, a resistance type electric furnace has an electrode 1, an electrode lifting device 2 for vertically moving the electrode (only a portion is shown), a furnace wall 3 for storing a material to be melted 5, a furnace bottom 4, and a raw material charging port 7. It consists of a lid 6, an electrode 1, a furnace wall 3, a power source (not shown) connected to the furnace bottom 4, and the like. The electrode 1 is inserted into the furnace through the furnace cover 6.
A sealing member (not shown) is usually arranged between the furnace wall 6 and the furnace wall 6. In order to melt and raise the temperature of the object 5 to be melted in this resistance type electric furnace, the electrode 1 is lowered to the position shown in the figure by the electrode lifting device 2, immersed in the object 5 to be melted, and energized. As a result, a current flows through the object to be melted 5, and the resistance heat of the current causes the object to be melted 5 to be melted and heated.

However, in the conventional resistance electric furnace mentioned above, when the electricity is on,
There was a drawback that the electrode 1 came into contact with the high-temperature air 8 in the furnace and underwent an oxidation reaction with oxygen in the air, resulting in local wear. As a preventive measure, inert gas such as nitrogen is blown into the furnace in order to release the oxygen that has entered the furnace outside the furnace. However, this was not a drastic countermeasure, and oxidative wear of the electrode 1 still occurred, resulting in an increase in running costs, which was viewed as a problem.

The present invention has been made in view of these problems of the prior art, and its object is to provide a resistance electric furnace that can reduce the amount of oxidation loss of electrodes.

The present invention, which has been made to achieve the above object, provides a resistance type electric furnace having an electrode inserted into the furnace through a furnace lid, and a sleeve extending into the furnace is provided around the outer periphery of the electrode, so that the sleeve is connected to the outer periphery of the electrode. The upper end of the sleeve is sealed against the electrode while the lower end is open, and an inlet for introducing a gas that does not react with the electrode is connected to the gap between the electrode and the sleeve. This is a resistance electric furnace characterized by the following features:

Hereinafter, the present invention will be explained in detail based on an embodiment shown in FIG. The resistance type electric furnace of this embodiment is similar to the conventional one, and includes an electrode 1, an electrode lifting device 2 for moving the electrode up and down, a furnace wall 3 and a furnace bottom 4 for storing a material to be melted 5, and a raw material charging port 7. It has a lid 6. However, unlike the conventional method, a sleeve 9 is attached to the outer periphery of the electrode 1. This sleeve 9 has an inner diameter slightly larger than the outer diameter of the electrode so that an annular gap 10 can be formed between the sleeve 9 and the outer circumference of the electrode 1, and when the electrode 1 is in the operating position shown, It extends inward and outward, and is provided so that its lower end is slightly immersed in the material to be melted 5. The upper end of the sleeve 9 is sealed and airtight to the electrode 1, while the lower end remains open. Furthermore, a gas inlet 11 connected to the gap 10 is provided near the upper end of the sleeve 9, and the inlet 11 is connected to a supply source (not shown) of a gas that does not react with the electrode, such as an inert gas. has been done. As the material constituting the sleeve 9, silicon carbide, silicon nitride, silicon nitride bonded silicon carbide, etc. can be used.

Next, a method of using the resistance electric furnace having the above structure will be explained. The electrode 1 and the sleeve 9 attached to it are lowered by the electrode lifting device 2 to the operating position shown in FIG. 2, and electricity is applied to the electrode 1 to melt the object 5 and
Raise the temperature. At the same time, a gas that does not react with the electrode is supplied to the gap 10 from the inlet 11 of the sleeve 9. The gap 10 is thus filled with a gas that does not react with the electrodes, preventing contact of the electrodes 1 with the high temperature oxygen in the furnace, and thus preventing oxidative wear of the electrodes 1.

In the above embodiment, the lower end of the sleeve 9 is immersed in the material to be melted 5, and the electrode 1 is completely isolated from the oxygen in the furnace, which is extremely preferable.
The present invention is not necessarily limited to this structure, and the lower end of the sleeve may be separated from the object 5 to be melted. Further, in the above embodiment, the sleeve 9 is attached to the electrode 1 and is shown to move up and down together with the electrode 1, but the sleeve 9 is fixed to the furnace lid 6 or other suitable member, and the electrode 1 is moved inside the sleeve 9. It is also possible to have a structure that raises and lowers. Furthermore, the sleeve 9 may be held by a separate lifting device so that it can be moved up and down separately from the electrode 1. In this way, when the material to be melted 5 is gradually taken out of the furnace for fiberization, as in the case of rock wool production, and the liquid level gradually decreases, the lowering of the liquid level can be followed. This is preferable because it allows the sleeve 9 to be lowered.

The resistance type electric furnace of the present invention can be used to re-melt crushed slag stone and adjust the composition and temperature to produce rock wool, or directly receive molten slag from a blast furnace and adjust the composition and temperature to produce rock wool. In addition to this, it can also be used to manufacture rock wool by melting natural rocks such as basalt and andesite, and to manufacture artificial stones other than rock wool. It can also be used for melting.

As explained above, the resistance electric furnace according to the present invention includes a sleeve extending into the furnace around the outer periphery of the electrode.
The structure is such that a gap is formed between the sleeve and the outer periphery of the electrode, and a gas that does not react with the electrode can be supplied into the gap between the electrode and the sleeve. It has the excellent effect of being able to protect the electrode and reducing the amount of oxidation loss of the electrode.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a conventional resistance electric furnace, and FIG. 2 is a schematic sectional view of an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Electrode, 2... Electrode lifting device, 3... Furnace wall, 4... Furnace bottom, 5... Material to be melted, 6... Furnace lid,
9... Sleeve, 10... Gap, 11... Inlet.

Claims (1)

[Claims] 1. In a resistance electric furnace having an electrode inserted into the furnace through a furnace lid, a sleeve extending into the furnace is provided around the outer periphery of the electrode so as to form a gap between the sleeve and the outer periphery of the electrode, and A resistance electric furnace characterized in that the upper end of the sleeve is sealed against the electrode while the lower end is open, and an inlet for introducing a gas that does not react with the electrode is connected to the gap between the electrode and the sleeve. .