JP2940133B2 - Melting status detection method for DC arc furnace - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a melting state of a raw material melted in a furnace in a DC arc furnace.

[Conventional technology]

In a DC arc furnace, an arc is generated between an upper electrode and a molten raw material charged in the furnace, and the arc melts the molten raw material. In the case of the melting, the upper electrode is lowered as the melting raw material progresses. Conventionally, the state of dissolution of the raw material in the furnace has been estimated from the upper and lower positions of the upper electrode.

[Problems to be solved by the invention]

In this conventional method for detecting the melting state of a DC arc furnace, the melting state of the molten raw material below the upper electrode is well understood, but the melting state of the molten raw material around the upper electrode is difficult to understand. For this reason, in the system for reloading the melted raw material based on the detection result, the previously melted raw material has already been completely melted, and unnecessary arc heating has been performed until then (useless power consumption is reduced). Uneconomical cost, or a large amount of undissolved raw material remains, and the amount of additional molten raw material becomes mountainous, resulting in a lot of loss time due to the furnace lid not closing. There was a problem.

The present invention has been made to solve the above-mentioned problems (technical problems) of the prior art, and the furnace wall at the part where melting of the molten material proceeds fastest on the side of the arc deflection direction in the furnace and the other parts thereof By measuring the magnitude of the temperature difference between the parts of the furnace wall, the melting state of the melted raw material can be detected with high accuracy, and as a result, the reloading of the melted raw material can be performed at an appropriate time, thereby saving energy. An object of the present invention is to provide a method for detecting a melting state of a DC arc furnace.

[Means for solving the problem]

In order to achieve the above object, a method for detecting the melting state of a DC arc furnace according to the present invention includes a furnace bottom electrode provided at a lower portion of a hollow furnace body, and an upper electrode provided at an upper portion, and both electrodes are provided. Each is connected to a power supply device via a conductor, to generate an arc between the upper electrode and the melted raw material charged in the furnace body by supplying a direct current to the two electrodes from the power supply device, In a DC arc furnace in which the melting material is melted by the arc, temperature sensing devices for detecting the temperature of the furnace wall are provided at a plurality of locations separated from each other on the furnace wall of the furnace body. At the same time, one of the attachment positions is set to a position in the direction of deflection of the arc due to the electromagnetic force exerted from the conductor, and during the melting of the molten raw material, the temperature sensing position in the position in the direction of change of the arc is changed. apparatus By measuring the magnitude of the temperature difference between the temperature of the furnace wall are respectively detected by the temperature sensing device provided at the other positions, in which to determine the dissolution conditions of the furnace body raw material for melting.

[Action]

The melted raw material is melted by an arc generated between the upper electrode and the melted raw material. The melting is the fastest on the side of the arc deflection direction. When all of the melted material on the side of the arc deflection direction is melted and the furnace wall on that side is exposed, the temperature of the furnace wall detected by the temperature sensing device attached to the furnace wall increases, and the temperature sensing in other places The difference from the furnace wall temperature detected by the device increases. Therefore, by knowing the increase in the temperature difference, it is possible to detect that all of the melted material on the side of the deflection direction of the arc has melted.

〔Example〕

Hereinafter, drawings showing an embodiment of the present application will be described. First
In FIG. 2 and FIG. 2, reference numeral 1 denotes a DC arc furnace. Reference numerals 2 to 23 indicate known members in a DC arc furnace. That is, reference numeral 2 denotes a furnace body, which is hollow from the furnace bottom 3 and the furnace wall 4, and has an interior as a raw material storage space 5 for storing a molten raw material. Reference numeral 6 denotes a furnace bottom electrode attached to a substantially central portion of the furnace bottom 3, reference numeral 7 denotes a tapping hole provided in a part of the furnace wall 4, reference numeral 8 denotes a tapping gutter, and reference numeral 9 denotes a working port. Reference numeral 10 denotes a furnace cover that covers the furnace body 2 and has an electrode hole 11. The upper electrode 12 is inserted into the electrode hole 11. Only one upper electrode 12 is provided. The upper electrode 12 is supported by an electrode support mechanism 13 so as to be vertically movable. The electrode support mechanism 13 has a well-known configuration, 14 is an electrode support, 15 is a lifting device, 16 is an electrode support arm, and 17 is an electrode holder. Next, a power supply system will be described.
Reference numeral 19 denotes a conductor having one end connected to the furnace bottom electrode 6, that is, a lower conductor;
Indicates the presence of a conductor provided along the support arm 16, that is, an upper conductor (referred to as a support bus).
Connected to Reference numerals 21 and 22 denote flexible electric wires connected to the other ends of the lower conductor 19 and the upper conductor 20, respectively. Reference numeral 23 denotes a transformer room, inside which a power supply device such as a furnace transformer is provided,
Flexible electric wires 21 and 22 connected to the lower conductor 19 and the upper conductor 20 are connected to the power supply device.

Next, a configuration for detecting the melting state provided to the DC arc furnace 1 will be described. 25 is a first water-cooled panel, 26 is a second water-cooled panel, which are mounted on the furnace wall 4 so as to form a part thereof, and each of them is connected to a supply pipe 27 and a drain pipe 28. . The first water-cooling panel 25 is provided at a location on the furnace wall in the direction of deflection of the arc A as described below (a location where the molten material melts fastest, that is, a location adjacent to the hot spot portion). Is provided at a location separated from the first water cooling panel 25, for example, at a location opposite to the first water cooling panel 25 in this example. Reference numeral 31 denotes a first temperature sensing device attached to the first water cooling panel 25 for detecting the temperature of the furnace wall at the position of the first water cooling panel 25. In the present embodiment, a system is used in which the difference in water temperature between the water supply and drainage of the first water-cooled panel 25 is measured to detect the heat flux on the panel surface of the first water-cooled panel 25. Reference numeral 32 denotes a second temperature sensing device attached to the second water cooling panel 26 for detecting the temperature of the furnace wall at the position of the second water cooling panel 26. Similar ones are used. Each of the temperature sensing devices includes a thermocouple or a side temperature resistor mounted on the inner surface of each of the water cooling panels 25 and 26 and located inside the furnace wall, and a temperature detector connected thereto. It may be.

The operation of the DC arc furnace will be described. First, the melted raw material 34 is charged into the space 5 on the furnace wall 3 (initial loading). Next, after covering the furnace lid 10, a DC current for arc generation is supplied from the power supply device to the furnace bottom electrode 6 and the upper electrode 12 via the lower conductor 19 and the upper conductor 20. Then, an arc A is generated between the furnace bottom electrode 6 and the upper electrode 12 or between the molten material 34 (for example, scrap) electrically connected to the furnace bottom electrode 6 and the upper electrode 12. The melting material 34 is melted by the heat of the arc A.

The dissolution situation is as follows. Upper electrode at the beginning of melting
The dissolving raw material 34 is dissolved over a range of about twice the diameter of the upper electrode centered on 12. The upper electrode 12 is lowered as such melting proceeds to the lower part of the melting raw material. Next, with the upper electrode 12 lowered, the melted raw material 34 is melted in the shape of a stalk, and the surrounding portion collapses. In this case, the melting of the melted raw material 34 on the deflection direction side of the arc A by the electromagnetic force exerted from the conductors 19 and 20 proceeds faster than other portions, and the first water-cooled panel 25 is exposed. Next, melting proceeds as a whole to form flat molten steel.

In the melting process as described above, if the amount of the undissolved raw material 34 in the space 5 decreases, the additional loading of the dissolved raw material (two
) Are performed as appropriate.

When the melting of the molten raw material is completed as described above and all of the molten steel is turned into molten steel, the furnace body 2 is tilted and tapping is performed from the tapping outlet 7.

Next, detection of the dissolution state in the above-described dissolution process will be described. During the melting, the first and second temperature sensing devices 31 and 32 detect the heat flux on the furnace wall at each attachment location. In this state, if the molten raw material 34 on the deflection direction side of the arc A is melted as described above,
The panel surface of the first water cooling panel 25 is exposed to the arc A. Then, the heat flux received by the surface increases. On the other hand, since the second water cooling panel 26 is not yet exposed, the heat flux remains small. For this reason, the difference between the heat fluxes detected by the two temperature sensing devices 31 and 32 increases, and the increase in the difference between the outputs of the respective temperature sensing devices 31 and 32 leads to an increase in the temperature difference between the furnace walls at the respective installation locations. Measured. By measuring such an increase in the temperature difference, it is possible to detect that the melting of the melted raw material 34 reaches the melted raw material adjacent to the first water-cooled panel 25.

When the above-described melting is detected, there is a difference in the time until the heat flux increases and the amount of power consumption depending on the type and shape of the melting raw material (scrap). Therefore,
By calculating the melting speed of the remaining scrap based on the time required for the heat flux to reach a certain value or the amount of power consumption, it is possible to accurately and easily determine the reloading and the melting. As a result, the next reloading and other steps can be performed at an appropriate time, and the amount of power consumption until the complete melting is completed and the loss time can be reduced.

Next, the determination of the location of the first and second water cooling panels 25 and 26 will be described. In a DC arc furnace, the arc A generated between the upper electrode 12 and the furnace bottom electrode 6 or the melted raw material 34 due to the electromagnetic force generated by the lower conductor 19, the upper conductor 20, and the like is directed in a certain direction according to Fleming's left-hand rule. To be deflected. The direction of the deflection can be determined by performing an electromagnetic analysis based on the positions of the transformer, the secondary conductor (the upper conductor 20 and the lower conductor 19), and the water-cooled cables 21 and 22. In addition, the direction can be freely changed by considering the arrangement of the secondary conductor. Water cooling panels 25 and 26 and temperature sensing devices 31 and 32
May be appropriately arranged under the conditions described above.

Next, the water-cooling panel and the temperature sensing device are arranged at a greater number of places on the furnace wall, and one of them is arranged at a place on the side of the arc deflection direction. By measuring the magnitude of the temperature difference between the temperature of the furnace wall detected by the temperature sensing device disposed at the location and the temperature sensing device disposed at other locations, the determination of the melting state as described above is performed. May go.

Next, FIG. 3 shows a different example of the arrangement of the first and second water-cooling panels 25e and 26e. The first water-cooling panel 25e is arranged on the side of the deflection direction of the arc Ae. 26e
Is located on the side next to it.

In addition, functionally considered to be the same or equivalent to those in the previous figure, the same reference numerals as those in the previous figure denote the same parts as in the previous figure.
And duplicated description is omitted.

Next, FIG. 4 shows an example of a change in the water supply / drainage temperature of the water cooling panel. As the temperature of the waste water changes as shown in the figure, the temperature difference between the temperature of the furnace wall on the deflection direction side of the arc and the temperature of the furnace wall on the other side is detected by the temperature sensing device as described above,
Thereby, the dissolution state of the dissolving raw material can be grasped. Therefore, based on the grasped state, the replenishment of the melted raw material can be performed as shown in the figure.

〔The invention's effect〕

As described above, in the present invention, during the melting of the molten raw material 34, the side of the deflection direction of the arc A, that is, the molten raw material 34
Because the temperature difference between the temperature of the furnace wall on the fastest melting side and the temperature of the furnace wall on the other side is measured, by measuring the increase in the temperature difference, It has the feature that it is possible to accurately detect that melting has reached the raw material for melting the cracks in the furnace wall 4. This means that the melting state of the melted raw material 34 in the furnace body can be accurately grasped. Based on the fact, it is possible to appropriately judge when to perform the reloading, and to eliminate the problems as in the prior art and contribute to energy saving. There is utility that can be done.

[Brief description of the drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a schematic vertical sectional view of a DC arc furnace, FIG. 2 is a horizontal sectional view of FIG.
FIG. 4 is a schematic plan view showing different examples of the arrangement position of the water cooling panel, and FIG. 4 is a graph showing an example of a change in supply / drain temperature of the water cooling panel. 2 ... Furnace body, 6 ... Furnace bottom electrode, 12 ... Top electrode, 31, 32
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Claims (1)

(57) [Claims] A furnace bottom electrode is provided at a lower part of a hollow furnace body, and an upper electrode is provided at an upper part thereof. The two electrodes are connected to a power supply through conductors respectively. An arc is generated between the upper electrode and the molten raw material charged in the furnace body by supplying a direct current to both electrodes, and the direct current arc furnace is configured to melt the molten raw material by the arc. On the furnace wall of the furnace body, temperature sensing devices for detecting the temperature of the furnace wall are respectively attached at a plurality of places separated from each other, and one of the attachment positions is determined by an electromagnetic force exerted from the conductor. At the position on the side of the arc deflection direction, during melting of the melting raw material, the temperature of the furnace wall is detected by the temperature sensing device at the position on the changing direction side of the arc and the temperature sensing device at the other position, respectively. Temperature temperature By measuring the large and small, dissolution conditions method of detecting a DC arc furnace, characterized in that to determine the dissolution conditions of the furnace body raw material for melting.