JPH04151489A - Method of sensing melted state in dc arc furnace - Google Patents

Abstract

PURPOSE:To perform additional loading of melting raw material at a proper time and save energy by a method wherein a difference between a temperature of a furnace wall detected by a temperature sensing device placed at an arc varying directional position and another temperature at another furnace wall detected by another temperature sensing device at another location is measured so as to judge a melting condition in the furnace. CONSTITUTION:During a melting operation, thermal flow fluxes at a furnace wall of each of accompanying installing locations are detected by the first and second temperature sensing devices 31 and 32. Under this condition, when a melting raw material 34 at a deflected direction of an arc A is melted completely, a panel surface of the first water-cooled panel 25 is exposed against the arc A. Then, a thermal flow flux received by that surface is increased. In turn, since the second water-cooled panel 26 is not exposed yet, the thermal flow fluxes are kept low. Due to this fact, a difference in thermal flowes detected by both temperature sensitive devices 31 and 32 is increased, thereby an increased difference in temperature at the furnace walls of each of the installing locations is measured in reference to an increased difference in outputs of each of the temperature sensitive devices 31 and 32. Measurement of such an increased difference in temperatures enables the melting of the melting raw material 34 to be detected and reached to the melting raw material adjacent to the first water-cooling panel 25.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detecting the state of melting of molten raw material melted in a furnace body in a DC arc furnace.

[Conventional technology]

In the rL flow arc furnace, an arc is emitted between the upper electrode and the molten raw material charged into the furnace, and the molten raw material is melted by the arc. In the case of melting, the upper electrode is lowered as the melting raw material progresses. Conventionally, the state of melting of the melted raw material in the furnace was estimated from the vertical position of this upper electrode.

[Sllg to be solved by the invention] This conventional method for detecting the melting state of a DC arc furnace has the problem that although the melting state of the melted raw material below the upper electrode can be clearly seen, it is difficult to understand the melting state of the melted raw material around it. Ta.

For this reason, in a system that sequentially charges molten raw materials based on the detection results, the previous molten raw materials have already been completely melted, and until then there was unnecessary arc heating (reducing electric power consumption). ), resulting in uneconomical effects such as
There was a problem that there was a lot of unmelted melted raw material remaining, and the melted raw materials in the multiple sets were piled up, and the furnace I could not be closed, resulting in a lot of lost time.

The present invention was made in order to solve the problems (technical problems) of the prior art described above, and it is possible to achieve 1 f! By measuring the temperature difference between the part of the furnace wall where the raw material is melting fastest and the other part of the furnace wall,
The dissolution status of melted raw materials can be detected with high accuracy, and as a result,
It is an object of the present invention to provide a method for detecting the melting state of a DC arc furnace, which enables continuous loading of melted raw materials at appropriate times and thereby saves energy.

[Means to solve problems]

In order to achieve the above object, the method for detecting the melting state of a DC arc furnace according to the present invention includes a bottom electrode at the bottom of the hollow furnace body, an upper electrode at the top, and the circular electrode each connected to a power supply device via a conductor, and by supplying a direct current from the power supply device to the circular electrode, an arc is generated between the upper electrode and the molten raw material charged into the furnace body; In a DC arc furnace in which the melting material is melted by the arc, temperature-sensing devices are attached to the furnace wall of the furnace body at multiple locations spaced apart from each other to detect the temperature of the furnace wall, respectively. At the same time, one of them is installed at a position on the side of the direction in which the arc is deflected by the electromagnetic force exerted from the conductor, and during melting of the melted raw material, one of the sensors is placed on the side in the direction of change of the arc. The state of melting of the melted raw material in the furnace body is determined by measuring the difference in temperature between the furnace wall temperatures detected by the temperature device and the temperature sensing device located at other locations.

[Effect]

The molten raw material is melted by an arc generated between the upper electrode and the molten raw material. The melting progresses faster on the side in the direction of arc deflection.When all the melted raw materials on the side in the direction of arc deflection are melted and the furnace wall on that side is exposed, a temperature sensing device attached to the furnace wall on that side is exposed. The furnace wall temperature detected by the furnace wall temperature increases, and the difference between the furnace wall temperature and the furnace wall temperature detected by the temperature sensing device at another location increases. Therefore, by knowing the increase in the temperature difference, it can be detected that all of the melted raw material on the side in the deflection direction of the arc has been melted.

〔Example〕

Below, the drawings showing the embodiments of the present application will be explained. In Figs. 1 and 2, 1 indicates a DC arc furnace, and the reference numeral 2
23 indicate well-known members in a DC arc furnace. That is, 2 is a furnace body, which is hollow and constituted by a furnace bottom 3 and a furnace wall 4, and the inside thereof is a raw material storage space 5 in which melted raw materials are stored. Reference numeral 6 indicates a furnace bottom electrode 7 attached to the approximate center of the furnace bottom 3, a tap hole provided on a part of the furnace wall 4, 8 represents a tap hole 9, and a working opening, and 10 represents a tap hole provided over the furnace body 2. With a hearth lid,
It has an electrode hole 11. The upper electrode 12 is in the electrode hole 11.
is inserted. Only one upper electrode 12 is provided. The upper electrode 12 is supported by an electrode support mechanism 13 so as to be movable up and down. The electrode support mechanism 13 has a well-known structure, with reference numeral 14 an electrode support, 15 a lifting device, 16 an electrode support arm, and 17 an electrode gripper.Next, the power supply system will be explained. 19 indicates the presence of a conductor, that is, a lower conductor, which has one end connected to the hearth bottom electrode 6, and 2° indicates the presence of a conductor, that is, an upper conductor (referred to as a support arm busbar) provided along the support arm 16; It is connected to the upper electrode 12. 2L 22
are flexible electric wires connected to the other ends of the lower conductor 19 and the upper conductor 20, respectively. Reference numeral 23 indicates a transformer room, in which a power supply device such as a furnace transformer is provided, and the power supply device includes a flexible electric wire 21 connected to the lower conductor 19 and the upper conductor 2o.
, 22 are connected.

Next, the configuration for detecting the state of melting attached to the DC arc furnace 1 will be explained. 25 is a first water-cooled panel, and 26 is a second water-cooled panel, which are attached to the furnace wall 4 so as to constitute a part thereof, and a water supply pipe 27 and a drain pipe 28 are connected to each of them. . The first water-cooled panel 25 is provided on the furnace wall at a location on the side of the deflection direction of the arc A as described below (a location adjacent to the part where the melted raw material melts fastest, that is, the honoto spot), and the second water-cooled panel 26 is provided at a location apart from the first water-cooled panel 25, for example, in this example, at a location on the opposite side from the first water-cooled panel 25. 31 is a first temperature sensing device attached to the first water cooling panel 25, and is for detecting the temperature of the furnace wall at the position of the first water cooling panel 25. In this example, the heat flux on the panel surface of the first water-cooled panel 25 is sensed by measuring the difference between the water temperatures of the water supplied to the first water-cooled panel 25 and the water temperature of the drain water. 32 is a second temperature sensing device attached to the second water cooling panel 26, which is for detecting the temperature of the furnace wall at the position of the second water cooling panel 26, and is different from the first temperature sensing device 31 described above. A similar one is used. The improved reporter thermosensing device consists of a thermocouple or resistance thermometer mounted on the inner surface of each of the water-cooled panels 25 and 26, located inside the furnace wall, and a temperature detector connected to it. There may be.

The operation of the above DC arc furnace will be explained. First, hearth bottom 3
A molten raw material 34 is charged into the upper space 5 (paddy bag). Next, after covering the furnace 110, 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 melted raw material 34 (for example, scrap) electrically connected to the furnace bottom electrode 6 and the upper electrode 12. The melted raw material 34 is melted by the heat of the arc A.

The dissolution situation is as follows. At the beginning of melting, the upper electrode 1
The melted raw material 34 is melted over a range approximately twice the diameter of the upper electrode centered on the upper electrode. The upper electrode 12 is lowered as such melting progresses to the lower part of the melted raw material 34. Next, in the lowered state, the upper electrode 12
It melts into a haze-like shape, and the parts around it collapse. In this case, the melting of the melted raw material 34 on the deflection direction side of the arc A due to the electromagnetic force exerted from the conductor 1920 progresses faster than in other parts, and the melting progresses as a whole until the first water-cooled panel 25 is exposed and becomes flat. It becomes molten steel.

In the melting process as described above, when the unmelted raw material 34 in the space 5 decreases, the melted raw material is continuously loaded (2 loads, 3 loads).
) will be carried out as appropriate.

When the melting of the molten raw materials is completed as described above and all of the material becomes molten steel, the furnace body 2 is tilted and steel is tapped from the tapping lower.

Next, detection of the melting state during the above-mentioned melting process will be described. During melting, the heat flux at the furnace wall at each attached location is detected by the first and second temperature sensing devices 31 and 32. In this state, if the melted raw material 34 on the deflection direction side of the arc A is melted as described above, the panel surface of the water-cooled panel 25 of Wl,1 is exposed to the arc A. This increases the heat flux that that surface receives. On the other hand, since the second water-cooled panel 26 is not exposed yet, the heat flux remains small. For this reason, both temperature sensing devices 31.3
2 increases, and from the increase in the difference in output of each temperature sensing device 3132, an increase in the temperature difference of the furnace wall at each attached location is measured. By measuring the increase in such a temperature difference, it is possible to detect that the melting of the melted raw material 34 has reached the melted raw material adjacent to the first water-cooled panel 25.

When the above-mentioned melting is detected, there are differences in the time and power consumption until the heat flux increases as described above, depending on the type and shape of the melted raw material (scrap). Therefore, W
By calculating the dissolution rate of the remaining scrap based on the time it takes for the % flux to reach a certain value or the amount of power consumption, it is possible to accurately and conveniently perform the reloading determination and melting determination. As a result, the next continuous mounting and other steps can be carried out at appropriate times, and it is possible to reduce power consumption and loss time until complete melting is completed.

Next, the determination of the installation locations of the first and second water cooling panels 25 and 26 will be explained. In a DC arc furnace,
Due to the electromagnetic force generated by the lower conductor 19, the upper conductor 20, etc., the arc A generated between the upper electrode 12 and the bottom electrode 6 or the molten raw material 34 is deflected in a certain direction according to Fleming's left-hand rule.

The direction of the deflection can be determined by electromagnetic analysis based on the positions of the variable LL secondary conductors (upper conductor 20, lower conductor 19) and the water-cooled cable 2122. Also, if we consider the secondary conductor arrangement,
Can change direction freely. The water cooling panels 25, 26 and the temperature sensing devices 31, 32 may be appropriately arranged under the conditions described above in accordance with this arc deflection direction.

Next, the water-cooled panels and temperature-sensing devices are installed at more locations on the furnace wall, and one of them is installed at a location on the side of the arc deflection direction. The temperature difference between the temperatures of the furnace wall detected by the temperature-sensing device installed at the location and the temperature-sensing device located at other locations is measured to determine the state of melting as described above. You may go.

Next, FIG. 3 shows the first and second water cooling panels 25e.

26e, in which the first water-cooled panel 25e is placed on the side in the direction of deflection of the arc Ae, and the second water-cooled panel 26e is placed next to it.

It should be noted that parts that are considered to have the same or equivalent structure as those in the previous figure in terms of function are given the same reference numerals as in the previous figure with the letter e, and redundant explanations are omitted.

Figure 4 shows an example of changes in the water supply and drainage temperature of the water-cooled panel. As the waste water temperature changes as shown in the figure, the temperature sensing device as mentioned above detects the temperature difference between the temperatures of various parts of the furnace wall on the arc deflection direction side and on the other side, and from this, the melting status of the melting raw material can be grasped. can do. Therefore, based on the grasped situation, it is possible to carry out continuous loading of melted raw materials as shown in the figure.

〔Effect of the invention〕

As described above, in the present invention, during the melting of the molten raw material 34, the side in the direction of deflection of the arc A, that is, the molten raw material 3
Since the temperature difference between the temperature of the furnace wall on the side where the melting progresses fastest and the temperature of the furnace wall on the other sides in step 4 is measured, by measuring the increase in the temperature difference, it is possible to determine the side where the melting is progressing the fastest. It has the advantage of being able to accurately detect that the melting has reached the melted raw material on the furnace wall 4. This means that the melting status of the melted raw material 34 in the furnace body can be accurately grasped, and based on this, it is possible to appropriately judge the point at which double loading should be carried out, and it is possible to eliminate the problems of the above-mentioned conventional technology and contribute to energy conservation. It has usefulness.

[Brief explanation of the drawing]

The drawings show an embodiment of the present application, and Fig. 1 is a schematic vertical cross-sectional view of a DC arc furnace, Fig. 2 is a horizontal cross-sectional view of Fig.
FIG. 4 is a schematic plan view showing examples of different arrangement positions of water-cooled panels, and FIG. 4 is a graph showing an example of changes in water supply and drainage temperature of the water-cooled panels. 2... Furnace body, 6... Hearth bottom electrode, 12... Upper electrode, 31.32... Temperature sensing device, 34... Molten V# raw material,
A-... Arc. Figure Figure Figure Figure Horse Figure ft n Darkness

Claims (1)

[Claims] A hearth bottom electrode is provided at the bottom of the hollow furnace body, and an upper electrode is provided at the top, and both of the electrodes are connected to a power supply device through conductors, so that direct current is supplied from the power supply device to the two electrodes. In a DC arc furnace, an arc is generated between an upper electrode and a molten raw material charged into the furnace body by supplying an electric current, and the molten raw material is melted by the arc. In this method, temperature-sensing devices each detecting the temperature of the furnace wall are attached to multiple locations separated from each other, and one of the locations is
It is set at a position on the side of the deflection direction of the arc due to the electromagnetic force exerted from the conductor, and during melting of the melted raw material,
By measuring the difference in the temperature of the furnace wall detected by the temperature sensing device located on the arc change direction side and the temperature sensing device located at other positions, the melting status of the melted raw material in the furnace body is determined. A method for detecting melting status in a DC arc furnace, characterized by determining.