JPH0785966A - Carbon electrode breakage sensing and reducing method for electric melting furnace - Google Patents

Abstract

PURPOSE:To subject a waste object smoothly to a melting process, eliminate blocking of a molten slag exhaust port with a broken electrode, and also reduce risk of electrode breakage by measuring the weight of a carbon electrode using a load cell, and subjecting the measurement to a computing process made by a computer device. CONSTITUTION:The weight of a carbon electrode 11 is measured at certain intervals using a load cell 61, and the measurement is fed to a computer device 71 to perform a computing process. If the result shows that the (n+1)'th measurement has steeply decreased from the n'th measurement, a motor 51 is driven with signals given by the computer device 71, and a drum 41 is rotated in the regular direction to take up a wire 21, and upon lifting the electrode 11, its weight is calculated again by the load cell 61, the result wherefrom is fed to the computer device 71 to undergo a recomputing process. Thereby breakage of the electrode 11 is sensed imediately and automaticaly so that the waste object is smoothly subjected to a melting process. Also the molten slag exhaust port is prevented from being blocked with eventually broken electrode 11, and further breakage of the electrode 11 can be reduced because it is not lowered with any unreasonable force.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting and reducing breakage of a carbon electrode in an electric melting furnace. Wastes such as incinerated ash of municipal solid waste and dust ash (fly ash) are melted by using an electric melting furnace such as an arc furnace or a resistance heating furnace in which a carbon electrode is inserted in the furnace. The present invention relates to a method of detecting breakage of a carbon electrode in such an electric melting furnace and reducing the breakage.

[0002]

2. Description of the Related Art When a waste material is melted in an electric melting furnace, the tip side of a carbon electrode is generally inserted into a covering layer formed of the waste material put into the electric melting furnace. In many cases, the breakage of the carbon electrode occurs on the tip side thereof, and therefore, in the above-mentioned state, it is very difficult to visually judge whether or not the carbon electrode is broken.
Therefore, conventionally, it is the actual situation that the breakage of the carbon electrode in the electric melting furnace as described above is conjectured as a result of the consumption condition and the like. However, in such a conventional method,
Since the melting process is performed while leaving the broken carbon electrode as it is, that is, the broken carbon electrode remains in the furnace, the smooth melting process is hindered, and for example, the smooth flow of the molten slag is hindered. There is a risk that the broken carbon electrode may block the molten slag discharge port, and needless to say, there is a drawback that the breakage of the carbon electrode cannot be reduced.

[0003]

The problem to be solved by the present invention is that the conventional method for inferring the breakage of the carbon electrode results in a trouble in the smooth melting process of the waste and, in some cases, the breakage. There is a risk that the carbon electrode may block the molten slag discharge port, and needless to say, the breakage of the carbon electrode cannot be reduced.

[0004]

According to the present invention, however, the weight of a carbon electrode is measured by a load cell interposed between wires for suspending the carbon electrode, and when the measured value is suddenly decreased, the carbon electrode is raised, The weight is re-weighed, and the case where the difference between the weighed value before the sudden decrease and the re-weighed value exceeds a certain allowable value is regarded as breakage of the carbon electrode, and the carbon electrode in the electric melting furnace is characterized by The present invention relates to a breakage detection and reduction method.

When the waste is melt-processed by using an electric melting furnace, a molten metal layer is formed in the lower layer of the furnace, a molten slag layer is formed in the middle to upper layers of the furnace, and in some cases, a molten salt layer is formed in the upper layer of the furnace. Each of them is usually formed with a covering layer of waste in the uppermost layer in the furnace, and when the tip side of the carbon electrode is thrust into the covering layer, the state of current flow or molten slag flow is confirmed. Accordingly, the carbon electrode, which is consumed in sequence, is lowered. In many cases, the breakage of the carbon electrode occurs at the additional portion of the carbon electrode, particularly at the distal end side additional portion.

In the present invention, the carbon electrode is suspended by a wire, and the wire is wound around a drum via a supporting roller. The motor is driven to rotate the drum, and the wire is unwound to lower the carbon electrode, and the wire is wound to raise the carbon electrode. A load cell is interposed in the wire, the load cell is connected to an arithmetic unit, and the arithmetic unit is connected to a motor.

The weight of the carbon electrode is continuously or intermittently measured by a load cell, and the measured value is input to a calculation device for calculation processing. As a result of the arithmetic processing, the n + 1th weighing value is n
If the value decreases abruptly compared with the measured value of the second time, the motor is driven by the signal from the arithmetic unit, the drum is rotated to wind the wire, and the carbon electrode is lifted. Re-weigh, input the re-weighed value to the arithmetic unit, and re-calculate. This is because it is unknown whether the sharp decrease in the measured value is caused by the breakage of the carbon electrode or simply by the looseness of the wire. For some reason, for example, when the melting process is temporarily stopped and restarted to replace the carbon electrode, the covering layer has entered the part where the carbon electrode originally existed, and the surface of the molten slag layer is fluidized. When the carbon electrode is lowered at the time of resumption, the tip side of the carbon electrode plunges into the covering layer or the molten slag layer having poor fluidity, and the wire becomes loose as a result. Then, the wire is once wound up, the carbon electrode is raised to eliminate the looseness of the wire, and then the weight of the carbon electrode is re-weighed. Then, as a result of the recalculation process, when the difference between the measured value before the sudden weight reduction (nth measured value) and the remeasured value exceeds a certain allowable value in consideration of the consumption amount of the carbon electrode, the measurement error, and the like. Considers that the sudden decrease in weight is caused by the breakage of the carbon electrode, stops the melting process, and picks up the broken carbon electrode from the furnace as needed. If the difference between the measured value before the sudden decrease in weight (n-th measured value) and the re-measured value is within a certain allowable value, it is considered that the sudden decrease in weight was caused by the slack of the wire, and the melting occurred. continue processing.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a system diagram schematically showing one embodiment of the present invention. In FIG. 1, an arc furnace is used to melt the waste. In the furnace, a molten metal layer A is formed in the lower layer, a molten slag layer B is formed in the upper layer, and a waste covering layer C is further formed in the uppermost layer, which are connected to an AC three-phase power source (not shown). Carbon electrodes 11, 12, and 13 are inserted. The carbon electrodes 12 and 13 are similar to the case of the carbon electrode 11, and therefore illustration and description thereof will be omitted. Is wound around the drum 41. The drum 41 rotates normally or reversely when driven by the motor 51, and when it rotates normally,
Winding up the wire 21 to raise the carbon electrode 11,
Further, when inverted, the wire 21 is unwound and the carbon electrode 11 is lowered. A load cell 61 is interposed in the wire 21 between the support roller 31 and the drum 41, and the load cell 61 is an arithmetic unit 71.
And the arithmetic unit 71 is connected to the motor 51.

As described above, for example, the weight of the carbon electrode 11 is intermittently measured by the load cell 61, and the measured value is input to the arithmetic unit 61 for arithmetic processing. As a result of the arithmetic processing, when the n + 1-th measured value sharply decreases in comparison with the n-th measured value, the motor 51 is driven by the signal issued from the arithmetic unit 71, the drum 41 is rotated in the forward direction, and the wire 21 is moved. After winding and raising the carbon electrode 11, the weight of the carbon electrode 11 is re-weighed by the load cell 61, the re-weighed value is input to the arithmetic unit 71, and re-calculation processing is performed. As a result of the recalculation process, when the difference between the weight value before the sudden weight decrease (nth weight value) and the reweight value exceeds a certain allowable value, the sudden decrease in weight is caused by the breakage of the carbon electrode 11. Therefore, the melting process is stopped. Further, when the difference between the weight value before the sudden weight reduction (n-th weight value) and the re-weighed value is within a certain allowable value, it is considered that the sudden weight reduction is caused by the slack of the wire 21. If necessary, an igniting agent such as carbon powder or Dalai powder is put into the furnace to make arc discharge easy to occur, and then the melting process is continued.

[0010]

As is apparent from the above, according to the present invention described above, the breakage of the carbon electrode can be immediately and automatically detected and necessary measures can be taken, so that the waste can be smoothly melted. Further, there is an effect that the broken carbon electrode does not have a risk of blocking the molten slag discharge port, and in particular, the carbon electrode is not forcedly lowered, so that there is an effect that the breakage can be reduced.

[Brief description of drawings]

FIG. 1 is a system diagram schematically showing an embodiment of the present invention.

[Explanation of symbols]

11, 12, 13 ... Carbon electrode, 21 ... Wire, 31, 32 ... Support roller, 41 ... Drum,
51 ... Motor, 61 ... Load cell, 71 ...
Computing device, A ... Molten metal layer, B ... Molten slag layer, C ... Covering layer

Claims (1)

[Claims] 1. The weight of a carbon electrode is measured by a load cell provided on a wire for suspending the carbon electrode, and when the measured value is suddenly reduced, the carbon electrode is raised and the weight is re-weighed before the sudden reduction. A method for detecting and reducing breakage of a carbon electrode in an electric melting furnace, wherein the case where the difference between the measured value and the re-measured value exceeds a certain allowable value is regarded as a breakage of the carbon electrode.