JPH06176866A - Control device for electrode of melting furnace - Google Patents

Abstract

PURPOSE:To provide an electrode control device for a melting furnace such as an ash melting arc furnace, etc., equipped with a single phase power supply circuit, whereby shortcircuiting resulting from variation in the molten metal surface level during the furnace operation can be well responded quickly. CONSTITUTION:Two electrodes 3A. 3B are independently supported in a furnace by electrode elevating/sinking devices 2A, 2B, and a constant impedance control is conducted so as to make constant the ratio of the arc voltage to arc current in an single phase power supply circuit using the electrodes 3A, 3B as two electrodes. Thereby the supporting level of the electrodes 3A, 3B is adjusted automatically. Voltometers 8A, 8B are furnished at the electrodes 3A, 3B to sense the arc voltages between them and the furnace body. When the arc current varies greately with shortcircuiting, the arc voltages of the two electrodes 3A, 3B are sensed by the voltometers 8A, 8B, and, the elevating/sinking motions of the electrode elevating/sinking device on the side where the voltage is not sunk abnormally are stopped temporarily.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode control device for a melting furnace such as an ash melting arc furnace, which is capable of coping with the occurrence of a short circuit due to fluctuations in the molten slag surface during operation.

[0002]

2. Description of the Related Art Ash ash melting furnaces that treat incinerated ash detoxify by charging the ash containing harmful substances such as wastes into a melting furnace, heating and melting by arc discharge, and cooling and solidifying the ash. It is known from Japanese Laid-Open Patent Publication No. 62-112911 and Japanese Laid-Open Patent Publication No. 3-181703.

By the way, in the above ash melting furnace, it is required to keep the input electric power, and hence the arc current, substantially constant in order to perform the melting work efficiently. Therefore, the electrode is controlled by a method called constant impedance control in which the electrode elevating device is automatically driven so that the ratio of the arc voltage and the arc current becomes constant to elevate the electrode.

[0004]

By the way, in a melting furnace electrode control apparatus of a single-phase circuit having two electrodes as two electrodes which hang down in the furnace, an electrode elevating device has been conventionally provided for each electrode, and is independently provided. The impedance is controlled to make the arc length constant, but the molten slag surface of the furnace slag becomes rippled, or the incineration ash around the electrode collapses, etc. Since fluctuations occur, there is a problem that it takes time for the other electrode, which is not short-circuited, to automatically move up and down similarly to the short-circuited electrode and become unstable, and to converge.

[0005]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above problems, and a single-phase power source in which two electrodes are independently supported in a furnace by an electrode elevating device and the electrodes serve as both electrodes In the melting furnace electrode control device in which the supporting height of both electrodes is automatically adjusted by constant impedance control so that the ratio of the arc voltage to the arc current of the circuit is constant, the voltage between the furnace body and the electrodes A voltmeter is provided to detect each electrode, and when the arc current fluctuates significantly due to the occurrence of a short circuit, the voltmeter detects the arc voltage of both electrodes and the corresponding voltage is not abnormally lowered. The feature is that the lifting operation is temporarily stopped.

[0006]

[Function] When the arc current fluctuates significantly, it is determined which electrode has caused a short circuit due to the change in the arc voltage between the furnace body and both electrodes, and the electrodes that are not found to have a short circuit are temporarily checked. By stopping the ascending / descending operation of the electrode elevating / lowering device, unnecessary electrode ascending / descending movements are eliminated and only the electrode on the short-circuited side is automatically adjusted.

[0007]

EXAMPLE An example of the melting furnace electrode control apparatus of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an electrode control device for this ash melting furnace. Reference numeral 1 is a melting furnace, 2A and 2B are electrode elevating devices, and 3A and 3B are supported by the electrode elevating devices and are respectively hung in the melting furnace 1. The rod-shaped electrodes 4A and 4B are electrode control devices that output an elevation command signal to the electrode elevation devices 2A and 2B.

Reference numeral 5 is a transformer for supplying electric power to the electrodes 3A and 3B. The transformer 5 is provided with a tap voltage setting device 6 capable of arbitrarily variably setting the secondary side voltage by tap switching, and its switching operation. Can set the applied voltage to the electrodes 3A and 3B.

Further, 7 is an ammeter for detecting an arc current provided in a power supply line to the electrodes 3A, 3B, and the electrode control devices 4A, 4B are the arc voltage and the current detected by the voltmeters 8A, 8B. An elevating command signal is output to the electrode elevating devices 2A and 2B so that the ratio with the arc current detected by the total 7 becomes constant. 8A and 8B are the furnace body and the electrode 3
It is a voltmeter that detects the arc voltage between A and 3B, respectively.

That is, the electrode elevating / lowering devices 2A and 2B adjust the heights of the electrodes 3A and 3B, respectively, in accordance with a command from the electrode control devices 4A and 4B, so that the impedance between the electrodes 3A and 3B and the molten metal surface is increased. It is automatically adjusted to a constant level to maintain the desired input power.

Therefore, in the present invention, in the melting furnace provided with the above-mentioned single-phase power supply circuit, the molten metal surface fluctuates due to the collapse of a large amount of incinerator ash and the corrugation of the molten slag surface due to the arc. When a short circuit current instantaneously flows due to a short circuit between the electrodes 3A and 3B due to a short circuit due to the like, and the arc current detected by the ammeter 7 fluctuates greatly, the electrode control device 4
A and 4B are operated as shown in the flow chart of FIG.

That is, when the stability of the arc current is denied in step a, an abnormality in the arc voltage between the furnace body and the electrode 3A detected by the voltmeter 8A is judged in step b, and this arc is discriminated. If the voltage is found to have dropped abnormally, the lifting operation of the electrode lifting device 2B is temporarily stopped and the height of the electrode 3B is fixed to the current value.

For this reason, only the other electrode elevating device 2A raises and lowers the electrode 3A by constant impedance control, and the gap between the electrode 3A and the molten slag surface is widened, thereby eliminating the short circuit of the electrode 3A.

When an abnormal decrease in the arc voltage between the electrode 3B of the furnace body detected by the voltmeter 8B is detected in step c, the lifting operation of the electrode lifting device 2A is temporarily stopped. Of the other electrode 3B
The short circuit is corrected by raising and lowering only the constant impedance control to widen the gap with the molten slag surface.

[0015]

As described above, the melting furnace electrode control apparatus of the present invention is a melting furnace electrode control apparatus equipped with a single-phase power supply circuit,
When the arc current fluctuates greatly due to the occurrence of a short circuit, by checking the arc voltage of both electrodes, only the electrode on the short circuit side automatically adjusts its supporting height by impedance control, and the other electrode temporarily has a constant height. By fixing the electrode to a short circuit, it is possible to quickly and automatically adjust the supporting height of only the electrode in which the short circuit has occurred to the short circuit state and eliminate the short circuit condition. Therefore, there is a beneficial effect that a stable operation can be performed without unnecessary up-and-down movement of the electrode in the non-short-circuited side.

[Brief description of drawings]

FIG. 1 is a block diagram of a melting furnace electrode control device according to the present invention.

FIG. 2 is a flowchart showing the operation of the melting furnace electrode control device according to the present invention.

[Explanation of symbols]

 1 Melting furnace 2A, 2B Electrode lifting device 3A, 3B Electrode 4A, 4B Electrode control device 5 Transformer 6 Tap voltage setting device 7 Ammeter 8A, 8B Voltmeter

Claims (1)

[Claims] 1. Two electrodes are independently supported in a furnace by an electrode elevating device, and a constant ratio of arc voltage and arc current of a single-phase power supply circuit having the electrodes as the two electrodes is fixed. In the melting furnace electrode control device in which the support height of both electrodes is automatically adjusted by controlling the impedance, a voltmeter for detecting the voltage between the furnace body and the electrodes for each electrode is provided, and the arc current is generated due to the occurrence of a short circuit. Melting furnace electrode control, in which the voltmeter detects the arc voltage of both electrodes and the lifting / lowering operation of the electrode lifting / lowering device on the side where the voltage is not abnormally lowered is temporarily stopped apparatus.