JP2683045B2 - Electric melting furnace starting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention provides a pair of first electrodes for electric heating spaced apart from each other in a material to be melted contained in a melting furnace. The present invention relates to a method for starting an electric melting furnace, in which a material to be melted in between is melted by discharge heating of a pair of second electrodes for arc discharge, and then electric current is applied to the material between the first electrodes.

[Conventional technology]

In the conventional starting method, an initial heating burner is provided to melt the melted material in both first electrodes, and the melted material between the electrode pairs is partially melted so that an initial current flows. Or, the pair of second electrodes is discharged in a state where they are arranged so as to face each other in a direction substantially orthogonal to the facing direction of the pair of first electrodes, and a molten material having a width across both the first electrodes is formed. Was there.

[Problems to be Solved by the Invention] However, in melting a material to be melted by a burner, energy loss is low due to a large heat radiation loss, and both second electrodes are discharged to extend between both first electrodes. A thicker electrode rod is used for the second electrode to form a melt of width, which is more energy efficient than heating by a burner,
Moreover, there is a drawback that the discharge power must be increased.

The object of the present invention is to reduce the discharge power and
Even if a thin electrode rod is used for the electrodes, the material to be melted between the first electrodes can be melted.

[Means for solving the problem]

Characteristic means of the starting method of the electric melting furnace in the present invention,
In order to melt the material to be melted between the first electrodes having a Joule heating power source, a pair of second electrodes having a dedicated arc power source,
In a state where they are arranged adjacent to each other or substantially concentrically with respect to the pair of the first electrodes, they are discharged substantially along the facing direction of the first electrodes to form a molten material extending between the first electrodes. The action and effect are as follows.

(Operation)

That is, a pair of second electrodes connected to the arc power source, which are respectively arranged adjacent to or substantially concentric with the pair of first electrodes, are discharged substantially along the facing direction of the first electrodes,
When the melt is formed between both the second electrodes, even if the width of the melt is small, the melt easily comes into contact with each of the first electrodes, and therefore the melt is interposed between the first electrodes. An electric current can be easily passed. Further, when the melt is filled between the first electrodes, the power can be switched to the Joule heating power supply to start the melting in an extremely short time.

〔The invention's effect〕

Therefore, in order to form a molten material across both the first electrodes, both the second electrodes can be formed by a thin electrode rod and can be arc-discharged and melted with a small discharge power. Is miniaturized, and in addition, for example, in the conventional method, since the thin electrode rods are used for both the second electrodes, the separation distance between the adjacent first electrodes is reduced, and the second electrodes are formed by the discharge. Although it is conceivable to reduce the width of the melt, in this case, in order to melt the melted material over a wide range in the electric melting furnace, it is necessary to arrange a large number of first electrodes. According to the present invention, even if the distance between the two first electrodes is increased, a molten material can be formed between the first electrodes due to the discharge of the thin second electrodes, so that a small number of the first electrodes can cover a wide range. Can melt the material to be melted While less the cost of the electrodes, can reduce power consumption by the arc discharge, it was possible to improve the economy. According to this method, a large-capacity arc is not required as compared with the case where the same power source and electrodes are used for activation, so that the power source device is downsized. In addition, the arc of the second electrode shifts from the arc to resistance heating as the distance between the electrodes gradually increases. In this case, however, melting progresses along the surface of the second electrode. The melt fills in a very short time between the electrodes, and also
Even if the second electrode tip is not completely filled with the melt, but only if the second electrode tip is filled with the melt to some extent, the heating can be easily and rapidly promoted by switching the power supply to the Joule heating power supply.

〔Example〕

 Next, embodiments of the present invention will be described with reference to the drawings.

As shown in FIGS. 1 to 4, a melted material (1) such as incineration ash from a sewage sludge incinerator or an urban refuse incinerator is stored in an electric resistance type electric melting furnace (2) and melted. In addition, before energizing between the pair of molybdenum electrodes for electric heating (3), (3) spaced apart from each other in the material to be melted, in the initial stage, a pair of carbon electrodes for arc discharge (4A), ( Four
Discharge heating by B), molybdenum electrode (3),
When the material (1) to be melted between (3) is melted and the molten material (5) is formed between both molybdenum electrodes (3) and (3), the molybdenum electrodes (3) and (3) are separated from the area between them. The method for starting an electric melting furnace in which the molten material is energized and the molten material is expanded by Joule heat is shown.

That is, the opposite side walls (2) of the electric melting furnace (2)
A pair of molybdenum electrodes (3), which are separately arranged and opposed to each other, are respectively attached to A) and (2A) at upper and lower two places, and a power supply device (6) is connected to each pair of molybdenum electrodes (3). Then, the upper molybdenum electrode (3) pair is concentrically fitted with the carbon electrodes (4A) and (4B), respectively, and protrudes from the tips of the molybdenum electrodes (3) in the axial core (P) direction. The carbon electrodes (4A) and (4B) are guided in a retractable manner. A roller (7) for moving the pair of carbon electrodes (4A) and (4B) into and out of a relative position is provided.

Then, in order to melt the material to be melted between the molybdenum electrodes (3) and (3), one of the carbon electrodes (4A) and (4B) (4A) is slightly less than the molybdenum electrode (3). By approaching the other projected side (4B) and applying a current of 200A at about 300V, the molybdenum electrodes (3) and (3) are discharged substantially along the facing direction of the two carbon electrodes (4A). ), (4B) to form a melt (5) (first
Figure), and while continuing to discharge both carbon electrodes (4A) and (4B), move one carbon electrode (4A) in a direction away from the other carbon electrode (4B), and melt the melt to both molybdenum electrodes. (3), (3) spread in the opposite direction (Fig. 2), and finally both ends of the melt contact both molybdenum electrodes (3), (3) (Fig. 3), arc discharge Gradually disappears, and both molybdenum electrodes (3),
During (3), it shifts to resistance heating by Joule heat. At this time, the voltage drops from about 300 V at arc discharge to about 100 V and switches to constant current control.

Further, if the molten material spreads between the pair of lower molybdenum electrodes (3) and (3) by the electric heating by the upper molybdenum electrodes (3) and (3) (FIG. 4),
An electric current is also applied to both lower molybdenum electrodes (3) and (3) to melt the entire material to be melted in the electric melting furnace (2).

(Another embodiment)

The molybdenum electrode (3) for resistance heating is used because it is more expensive than a carbon electrode but consumes less, but electrodes made of other materials may be used and they are collectively referred to as the first electrode. Further, the reason why the carbon electrode is used for the arc discharge that consumes a lot of electricity is that it is particularly inexpensive and that the amount of slag adhered to the surface is small. Therefore, an electrode made of a material other than carbon may be used. Collectively referred to as an electrode.

The pair of second electrodes (4A) and (4B) with respect to the pair of first electrodes (3) and (3) are separately arranged concentrically, as shown in FIG. They may be adjacent to each other, that is, as long as the discharges of the second electrodes (4A) and (4B) are substantially along the facing direction of the first electrodes (3) and (3).

Both first electrodes (3), (3) and both second electrodes (4)
The facing directions of A) and (4B) may be the vertical direction or the diagonal direction other than the lateral direction.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the structure shown in the attached drawings.

[Brief description of the drawings]

The drawings show an embodiment of a method for starting a melting furnace according to the present invention,
FIG. 1 to FIG. 4 are operation explanatory views showing a vertical section of the melting furnace, and FIG. 5 is a vertical sectional view of a melting furnace of another embodiment. (1) …… Melting object, (2) …… Melting furnace, (3) …… First electrode, (4A), (4B) …… Second electrode, (5) …… Melting material.

Claims (1)

(57) [Claims] 1. A pair of first electrodes for electric heating (3), (3) are arranged apart from each other in a material to be melted (1) housed in a melting furnace (2). The melted material (1) between (3) and (3) is transferred to the pair of second electrodes (4) for arc discharge.
A method for starting an electric melting furnace in which electric current is applied to the melted material between the first electrodes (3) and (3) after melting by the discharge heating of (A) and (4B). ), (3)
In order to melt the material (1) to be melted between the pair of second electrodes (4A) and (4B), the pair of first electrodes (3) and (3)
In the state where they are arranged adjacent to each other or nearly concentrically,
Starting of an electric melting furnace in which a discharge (5) is formed across the first electrodes (3), (3) by causing a discharge substantially along the facing direction of the first electrodes (3), (3). Method.