JP2008116066A - Operating method of electric furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an operating method of an electric furnace having superior melting efficiency and electric power consumption rate. <P>SOLUTION: A furnace profile 20 is created by connecting positions in a furnace body 4, of a predetermined temperature as a melting temperature of crust 8, a position of an electrode 5 in the furnace body is determined, and the positions of the furnace profile and the electrode in the furnace body are made visible. Raw materials are additionally charged into the furnace body, or operating conditions relating to the electrode are adjusted on the basis of a situation in the visible furnace. Troubles such as bridging can be prevented by adjusting the operating conditions. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for operating an electric furnace for electrically melting a material to be dissolved.

  As a melting method to melt the melted material using a plurality of electrodes provided so that the melted material is inserted into the furnace body and inserted into the furnace body, an arc is generated between the electrode and the melted material. Electric arc furnace that melts by the heat of the arc, electric that is melted by immersing the electrode inserted into the furnace body into the object to be melted, and generating resistance heat by directly energizing the object to be melted from the electrode There is a method using a resistance furnace.

  A melting method using an electric arc furnace is used, for example, for melting scrap which is a steelmaking raw material. A melting method using an electric resistance furnace is used for melting solidified slag (see Patent Document 1), industrial waste (see Patent Document 2), incinerated ash (see Patent Document 3), and the like.

  By the way, in the production process of stainless steel, which is a kind of steel product, a large amount of by-products such as dust collection dust and pickling sludge are generated. By-products are useful because they contain metal components, and attempts have been made to recycle by-products, which have been disposed of as industrial waste, as raw materials for stainless steel. When reusing the above-mentioned by-product as a raw material for steelmaking, a method of melting using an electric resistance furnace has been considered because of its electrical characteristics and shape characteristics of being fine particles.

  FIG. 13 shows a configuration of the electric resistance furnace 1 used for melting by-products. The electric resistance furnace 1 includes a furnace body 4 having an opening 2 formed upward and an inner surface lined with a refractory material 3, and a raw material that is inserted into the furnace body 4 through the opening 2 and is a by-product in the furnace body. And a rod-shaped electrode 5 for energizing. Since the electric resistance furnace 1 includes the three electrodes 5, the individual electrodes are represented by 5 a, 5 b, and 5 c, respectively.

  The method of melting the raw material in the electric resistance furnace 1, that is, the operation method is as follows. In the electric resistance furnace 1, the electrode 5 is immersed in the raw material in the furnace body, and a three-phase alternating current is supplied between the three electrodes 5a, 5b, 5c. The raw material is dissolved. As the melting of the raw material proceeds, the raw material is additionally charged into the furnace body from the opening 2 using a shooter. When the raw material is repeatedly added and the melted raw material in the furnace body reaches a certain amount, the power supply to the electrode 5 is stopped and the tap formed in advance so as to penetrate the furnace body 4 and the refractory material 3 The sealing material 7 packed in the hole 6 is removed, and the metal component of the raw material dissolved from the tap hole 6 is discharged. In addition, after letting out a metal component, the molten slag produced | generated on the layer of a metal component in the furnace body is also taken out from the tap hole 6, and is removed.

  At the time of additional charging of the raw material in the operation of the electric resistance furnace 1, a predetermined timing is determined while the furnace operator imagines the inside of the furnace based on the appearance obtained visually through the opening 2. A predetermined amount of raw material is introduced.

  In the electric resistance furnace 1, current flows between the electrodes, so that the current flows most in the vicinity of the tip of the electrode 5. Therefore, the temperature distribution in the furnace body is not necessarily uniform, and a portion having a relatively low temperature may occur. Such a low temperature part is likely to occur near the furnace wall made of the refractory material 3, and the material 8 may adhere to the furnace wall and the mass 8 may be generated. This lump is sometimes called a crust. When the crust 8 is generated and grows toward the inside of the furnace body 4, the effective area in the furnace that can be used for melting is reduced when considered in a planar manner, and the contents of the furnace when considered three-dimensionally. The product decreases.

  Since the raw material is additionally charged based only on the visual appearance from the opening 2, the raw material may be charged into a portion where the furnace area is reduced. In such a case, the charged raw material cannot be smoothly dropped to a region near the tip of the electrode 5 where the resistance heat generation is high and the temperature is high. As a result, the raw material to be additionally charged cannot be dissolved by sequential resistance heat generation, and the raw material cannot be efficiently dissolved.

  Furthermore, when the charged raw material stays in the area where the furnace area is reduced and is softened and integrated without being melted, a so-called shelf suspension is formed in which the opening 2 is closed like a lid. There is. When the shelf suspension is formed, the raw materials to be introduced thereafter are deposited on the shelf suspension and cannot reach the region near the tip portion of the electrode 5 where the resistance heat generation is high and the temperature is high. Further, most of the resistance heat generated by energization from the electrode 5 is spent on raising the temperature of the raw material existing in the furnace and below the shelf suspension, so that the material below the shelf suspension is overheated. . When the shelf suspension melts and collapses at once due to the heat conduction and radiation from the overheated material, the undissolved material deposited on the shelf suspension falls into the dissolved material. A phenomenon in which a gas generated by a rapid reaction with an overheated raw material in which a raw material dropped from a shelf is melted and the raw material itself is ejected outward from the furnace body is called blowing up. When blow-up occurs, the heat in the furnace body is taken out by the scattered raw material and gas, so that heat loss increases and the melting efficiency of the raw material further decreases.

  As described above, when the crust 8 grows and operates in a state in which the area and volume of the furnace are reduced, there is a problem that the melting efficiency of the raw material is reduced, the raw material melting processing amount is reduced, and the power consumption is increased. .

  In the conventional operation method, the electrode 5 is moved up and down by automatic control to make the current value substantially constant regardless of the position where the crust 8 grows and the area and volume in the furnace are reduced. That is, when the depth of penetration of the electrode 5 into the raw material is deep, the raw material temperature at the deep position is high, and the current-carrying area of the electrode 5 is increased and the resistance is reduced, so that a large amount of current flows. In such a case, the electrode 5 is raised so that the current value decreases to a predetermined value, and the immersion depth of the electrode 5 with respect to the raw material is controlled to be shallow. On the other hand, when the immersion depth of the electrode 5 into the raw material is shallow and the current value is smaller than a predetermined value, the electrode is controlled to be lowered in the reverse manner. As a result, the immersion depth of the electrode 5 with respect to the raw material is kept substantially constant, but the electrode 5 is moved up and down regardless of the growth position of the crust 8, so that there is a problem such as a decrease in melting efficiency as described above. Occurs.

In the prior art related to blast furnaces generally used for melting iron materials, a plurality of temperature sensors are provided in the refractory that constitutes the furnace bottom and furnace wall, and heat transfer analysis is performed based on the measured values from the temperature sensors. There is a technique for predicting the erosion shape of the bottom refractory and the solidified layer shape of the melt in the furnace generated on the bottom refractory (see, for example, Patent Document 4 and Patent Document 5).
JP 58-173379 A JP 449033 A JP-A-2005-332121 JP-A-7-278632 JP-A-9-67607

  In Patent Document 4 and Patent Document 5, since the life of the bottom refractory determines the high furnace life, the erosion shape of the bottom refractory and the solidified layer shape of the melt in the furnace generated on the bottom refractory are predicted. It is disclosed to improve the accuracy of blast furnace life diagnosis by improving accuracy.

  Patent Document 4 and Patent Document 5 both disclose that the in-furnace situation is estimated, but the estimated in-furnace condition is merely used for predicting or extending the life of the bottom refractory and thus the blast furnace. The idea of improving the melting efficiency of the raw material in the furnace is not disclosed or suggested at all.

  An object of the present invention is to provide a method for operating an electric furnace that is excellent in melting efficiency and power consumption, and causes less trouble such as shelf hanging.

  The inventors of the present invention have created an in-furnace profile formed by connecting a predetermined temperature position in the furnace body obtained from a heat conduction calculation based on the heat flow transmitted in the thickness direction of the furnace wall, and the furnace profile is used to create a furnace profile. By grasping the internal conditions, adding raw materials, and moving the electrode position to an appropriate position and energizing can realize efficient melting of raw materials and prevention of troubles such as shelf hanging. As a result, the present invention has been completed.

  The operating method of the present invention is an electric furnace operating method in which electricity is passed between a plurality of electrodes in a furnace to melt the material to be melted interposed between the electrodes, and the material to be melted adheres to the inner wall of the furnace body. Create a furnace profile by concatenating the position of the temperature determined in advance as the melting temperature of the lump produced in this way, visualize the furnace profile and the position of the electrode, and based on the visualized furnace profile and the position of the electrode It is characterized by adjusting the operating conditions.

  The adjustment of the operating conditions is performed with respect to additional charging of the material to be melted into the furnace body. The operation conditions are adjusted with respect to the electrodes.

  At least a part of the plurality of electrodes is provided so as to be relatively displaceable with respect to the furnace body, and the adjustment of the operating condition relating to the electrodes is performed by displacing the relatively displaceable electrodes.

  A temperature detected by distributing a plurality of measurement points on the furnace wall of the furnace body and providing a plurality of temperature sensors in the thickness direction of the furnace wall at each measurement point, the temperature position predetermined as the melting temperature of the mass. It is obtained by calculating heat conduction using.

  According to the operation method of the electric furnace of the present invention, the melting efficiency is high and the processing capacity is excellent, the power unit is kept low, and trouble such as shelf hanging can be prevented.

  FIG. 1 shows a simplified configuration of an electric furnace 10 that is preferably used for carrying out the operation method of the present invention.

  An electric furnace 10 preferably used for the operation method of the present invention includes an electric resistance furnace 11 and a visualization device 12. The visualization device 12 creates and displays the in-furnace profile 20 as will be described later. In the electric resistance furnace 11 shown in FIG. 1, portions corresponding to the electric resistance furnace 1 shown in FIG. 13 are denoted by the same reference numerals, and redundant description is omitted. The electric furnace 10 is used for melting a steelmaking raw material which is a by-product generated in a stainless steel production process.

  The electric resistance furnace 11 includes a furnace body 4 whose inner surface is lined with a refractory material 3, three rod-like electrodes 5, an electrode lifting device 21 that moves the electrode 5 up and down relative to the furnace body 4, and A lifting amount measuring instrument 22 that measures the lifting amount of the electrode 5 and a plurality of temperature sensors 23 provided inside the refractory material 3 are included. The electric resistance furnace 11 may be provided with a furnace lid above the opening 2. Although not shown in FIG. 1, the electric resistance furnace 11 is surrounded by a power source for supplying power to the electrode 5, a shooter for feeding raw materials into the furnace body, and other furnace operations. Necessary equipment and devices are provided.

  The furnace body 4 is a container-like structure body made of steel, having a substantially cylindrical shape, and having an opening 2 formed above. The bottom and side walls of the furnace body 4 are lined with a refractory material 3. In the electric resistance furnace 11, a regular refractory brick 3 a and an irregular refractory 3 b are used as the refractory material 3.

  The electrode 5 is made of carbon and has a columnar or cylindrical shape. The electrode 5 is provided with a so-called holder which is a terminal 24 for energization at a predetermined position in the length direction. As described above, a cable (not shown) is connected to the terminal 24, and a power source is connected via the cable, and power is supplied from the power source.

  The end of the electrode 5 opposite to the end located in the furnace body is attached to the holding member 25. The holding member 25 is moved up and down by driving the electrode lifting device 21. The electrode lifting device 21 includes a lifting drive unit 26 and an operation unit 27. The lifting / lowering measuring instrument 22 is provided between the lifting / lowering drive unit 26 and the holding member 25 and measures the amount of displacement by which the electrode 5 moves up and down. By operating the raising / lowering driving unit 26 from the operation unit 27, the electrodes 5 can be individually raised and lowered one by one, or three electrodes can be raised and lowered together.

  For the temperature sensor 23, for example, an alumel-chromel thermocouple is used. The thermocouple is not limited to alumel-chromel, and may be another type of thermocouple such as platinum-platinum / rhodium. The temperature sensor 23 is not limited to a thermocouple, and any other sensor may be used as long as it can withstand high temperatures and measure temperature.

  FIG. 2 shows a position where the thermocouple 23 is provided in the circumferential direction in the furnace body. The thermocouples 23 are arranged at 14 locations at appropriate intervals in the circumferential direction in the furnace body. The position in the circumferential direction where the thermocouple 23 is disposed and the number of places where the thermocouple 23 is disposed are not particularly limited, but the thermocouple 23 is preferably disposed over the entire circumferential direction in the furnace. This is because the situation inside the furnace can be grasped over the entire circumferential direction.

  In FIG. 2, a region 28 scattered around the electrode 5 and surrounded by an imaginary line represents a position where the raw material is charged from the shooter into the furnace body. In the electric resistance furnace 11, the raw material charging positions are set at nine locations.

  The thermocouple 23 is provided at four positions in the ascending / descending direction of the electrode 5 at each position of the installation position along the inner periphery of the furnace body 4. In FIG. 1, the positions where the thermocouples 23 are provided in the electrode elevation direction are represented as A, B, C, and D in order from the shallower side to the deeper side of the furnace. The positions A to D at which the thermocouple 23 is provided in the ascending / descending direction of the electrode 5 are desirably arranged over the ascending / descending range of the electrode 5, particularly the range where the tip portion of the electrode 5 located in the furnace body ascends / descends. This is because the situation inside the furnace is grasped also in the electrode ascending / descending direction so that the position where the electrode tip portion where the heat generation amount becomes the largest when energized should be arranged can be specified.

  FIG. 3 shows a position where the thermocouple 23 is provided in the thickness direction of the refractory material 3. The thermocouple 23 is installed by selecting two different positions in the thickness direction of the refractory material 3 at one installation location in the electrode elevation direction. In order to create the in-furnace profile by the in-furnace profile creation device 31 to be described later, the temperature is measured at different positions in the thickness direction of the refractory material 3 constituting the side wall of the furnace body 4, and the thickness direction of the refractory material 3 is measured. The heat flow of must be determined. Therefore, it is necessary to install at least two thermocouples 23 in the thickness direction of the refractory material 3.

  The visualization device 12 includes an in-furnace profile creation device 31, a graphic processing device 32, and a display device 33. The in-furnace profile creation device 31 includes an in-furnace profile calculation unit 34 and an input unit 35. The input unit 35 is configured by a keyboard or the like, for example, and can input the thermal conductivity of the refractory material 3 and the crust 8 and the thickness of the refractory material 3 to the in-furnace profile calculation unit 34.

  The in-furnace profile calculation unit 34 performs heat conduction calculation using the data input from the input unit 35 and the temperature detected by the thermocouple 23, and has a predetermined temperature as the melting temperature of the crust 8 in the furnace body. The position is calculated, and the in-furnace profile 20 formed by connecting the positions is created.

  The graphic processing device 32 includes a graphic processing unit 36 and an input unit 37. The input unit 37 is configured by a keyboard or the like, for example, and can input the length and diameter as dimensions of the electrode 5 to the graphic processing unit 36. The graphic processing unit 36 performs graphic processing based on input data, that is, converts input data into image information. The in-furnace profile created by the in-furnace profile creation device 31 is output to the graphic processor 36 and converted into image information by the graphic processor 36. Further, in the graphic processing device 32, the electrode position in the furnace body estimated based on the electrode length and the operation of the electrode lifting / lowering device 21 can be graphed.

  The graphic processing device 32 can also graph only the in-furnace profile or the electrode position, or can collect and graph the in-furnace profile and the electrode position together.

  The display device 33 is realized by a liquid crystal display or a cathode ray tube, for example, and receives image information output from the graphic processing device 32 and displays it as a visible image. The display device 33 may further include a printer.

  Before the description of the operation method of the present invention, the melting operation in the electric resistance furnace 11 will be briefly described. Before the start of melting, the tip of the electrode 5 is located at the same depth as the tap hole 6, and in this state, the raw material and the reducing agent in the furnace body, and, if necessary, slag components such as a fouling agent Adjustment material is introduced.

  Next, power is supplied from the power source to the electrode 5 and electricity is passed between the electrodes, thereby causing a current to flow directly through the raw material. The raw materials and the like are dissolved by utilizing the resistance heat generated in the raw materials and the like by direct energization. As melting of the raw material or the like proceeds, additional raw material is charged into the furnace, and the charged raw material is sequentially melted. When the melted raw material, particularly the metal component reaches a certain amount, the power supply to the electrode 5 is stopped, and the melted metal component and molten slag are discharged from the tap hole 6.

  The electric resistance furnace 11 is repeatedly executed as a series of operations from the initial charging of raw materials and the like until the molten metal component and molten slag are discharged out of the furnace. The series of operations is called charging.

  The method of the present invention is an operation method of the electric furnace 10 in which a raw material which is a material to be dissolved interposed between electrodes is melted by energizing between a plurality of electrodes in the furnace body, and the raw material is applied to the inner wall of the furnace body 4. The in-furnace profile 20 is created by concatenating the position of the temperature that is predetermined as the melting temperature of the crust 8 generated by fixing, the in-furnace profile 20 and the position of the electrode 5 are visualized, and the in-furnace profile 20 that is visualized Based on the position of the electrode 5, the operating conditions are adjusted.

  In the creation of the in-furnace profile, the position in the furnace body at a temperature predetermined as the melting temperature of the crust 8 is distributed over the furnace wall of the furnace body 4 as described above, and the thickness of the furnace wall is measured at each measurement place. It is calculated | required by providing heat conduction calculation using the temperature detected by providing the several thermocouple 23 in a vertical direction.

  FIG. 4 explains how to obtain the in-furnace profile in the in-furnace profile creation device 31. Note that FIG. 4 shows a cross-section at one location in the circumferential direction of the furnace body 4 and one location in the electrode elevation direction among locations where the thermocouple 23 is installed. In the electric resistance furnace 11 illustrated in FIG. 4, the basic refractory material layer 41, the first refractory brick layer 42, the second refractory brick layer 43, the third refractory brick layer 44, and the stamp layer 45 stamped with the irregular refractory material. There are five layers of the refractory material 3 and a crust 8 that is a raw material fixed to the furnace body side.

  In FIG. 4, λ1 to λ5 are the thermal conductivities of the refractory brick layers 42 to 44, the stamp layer 45, and the crust 8, and b1 to b5 are the thicknesses of the respective layers.

  The thermocouple 23 has two locations in the thickness direction of the refractory material 3, that is, between the basic refractory material layer 41 and the first refractory brick layer 42, and between the second refractory brick layer 43 and the third refractory brick layer 44. Between. The thermocouple 23 installed between the basic refractory material layer 41 and the first refractory brick layer 42 is the thermocouple 23α, and the thermocouple 23 installed between the second refractory brick layer 43 and the third refractory brick layer 44. Is represented by a thermocouple 23β.

  The temperature measurement results by the thermocouples 23α and 23β are input to the in-furnace profile calculation unit 34. The in-furnace profile is obtained based on the temperature measurement result and the thermal conductivity and thickness data input from the input unit 35. In the illustration of FIG. 4, the temperature predetermined as the melting temperature of the crust 8 is 1200 ° C. The melting point of the crust 8 varies depending on its composition, but it can be obtained in advance by taking the crust 8 adhering to the furnace wall and performing a Zegel cone test or the like.

  Next, how to obtain the in-furnace profile in the in-furnace profile calculation unit 34 will be described. In obtaining the in-furnace profile, it is assumed that the heat flow rate Q in the direction perpendicular to the side wall of the furnace body 4 is constant.

First, the heat flow rate Q in the direction perpendicular to the side wall of the furnace body 4 is calculated using the temperature measurement results t1 and t3 of the thermocouples 23α and 23β. A basic equation for obtaining the heat flow rate Q is given by equation (1).
Q = K · ΔT (1)
Where, K: heat flow rate
ΔT: temperature difference between front and back of each layer [deg]
Q: Heat flow rate [Kcal / m ² · h]

Since the thermal conductivity K in the first and second refractory brick layers 42 and 43 is given by equation (2) using the respective thermal conductivity and thickness, the heat flow rate Q is obtained by equation (3).
1 / K = b1 / λ1 + b2 / λ2 (2)
Q = K · (t3−t1) (3)

Since the heat flow rate Q is assumed to be constant, the temperature of the layer boundary where no thermocouple is installed from the following equations (4) to (6) using the thermal conductivity λ of each layer and the thickness b. t2, t4, and t5 are obtained.
Q = λ2 / b2 / (t3-t2) (4)
Q = λ3 / b3 · (t4-t3) (5)
Q = λ4 / b4 · (t5-t4) (6)

When t5 is 1200 ° C. or less, the thickness b5 of the crust 8 indicating the melting position of the crust 8 is on the non-eroded surface of the stamp layer 45 or somewhere in the thickness direction of the crust 8, 7).
Q = λ5 / b5 · (1200−t5) (7)

When t5 exceeds 1200 ° C., it indicates that the crust 8 is completely melted, the stamp layer 45 is eroded, and the position where the temperature reaches 1200 ° C. is somewhere in the stamp layer 45. Thickness bx is calculated | required by Formula (8).
Q = λ4 / bx · (1200−t4) (8)

In the electric resistance furnace 11 illustrated in FIG. 4, since the thickness from the basic refractory material layer 41 to the second refractory brick layer 43 is 0.25 m, the distance to the in-furnace position at 1200 ° C. L is obtained by equation (9) when t5 is 1200 ° C. or lower, and is obtained by equation (10) when t5 exceeds 1200 ° C.
L = (0.25 + b3 + b4 + b5) (9)
L = (0.25 + b3 + bx) (10)

  An example of calculation based on the actual measurement data shown in Table 1 and Table 2 is shown below. The refractory brick layer shown in Table 1 is made of chamotte brick, and the stamp layer is made of carbon paste.

From the above equations (2) and (3), the heat transmissivity K and the heat flow rate Q are obtained.
1 / K = 0.065 / 0.84 + 0.115 / 0.92 to K = 4.9,
From Q = 4.9 (679.8-266.8) to Q = 2023.7.

  Hereinafter, using this heat flow rate Q, temperatures t2, t4, and t5 are obtained from the above equations (4) to (6) as follows. t2 = 426.8.degree. C., t4 = 909.5.degree. C., t5 = 11219.8.degree. Since t5 exceeds 1200 ° C., the position at which the temperature in the furnace reaches 1200 ° C. is obtained by the above equation (8).

  From 2023.7 = 4.5 / bx (1200-909.5), bx = 0.646. Therefore, the distance L to the in-furnace position at 1200 ° C. is L = (0.25 + 0.115 + 0.646) = 1.010 m from the above equation (10).

  In the in-furnace profile creation device 31, the above calculation is performed for all the locations where the thermocouples 23 are installed, and an in-furnace profile formed by connecting positions at 1200 ° C. in the furnace is created.

  The in-furnace profile created by the in-furnace profile creation device 31 is output to the graphic processor 36 and converted into image information by the graphic processor 36. The in-furnace profile converted into image information by the graphic processing unit 36 is further output from the graphic processing unit 36 to the display device 33, and is made a visible image by the display device 33.

  In addition, here, when the graphic processing device 32 is made into a graphic, the distance L obtained by the in-furnace profile creation device 31 is subtracted from 3.5 m which is the radius of the furnace body 4 having a cylindrical shape, and the center of the furnace body 4 is obtained. The in-furnace profile is expressed as the distance from.

  An example of the in-furnace profile visualized by the display device 33 is shown in FIGS. FIG. 5 is an in-furnace profile viewed from the upper surface of the electric resistance furnace 11. FIG. 5 shows the in-furnace profiles in the circumferential direction of the furnace at different positions A, B and C among the thermocouple installation locations in the electrode elevation direction shown in FIG. The first curve 51 in FIG. 5 shows the in-furnace profile at the A position, the second curve 52 represents the B position, and the third curve 53 represents the in-furnace profile at the C position. As shown in FIG. 2, the thermocouples 23 are installed at 14 locations in the circumferential direction of the furnace. In FIG. 5, the in-furnace profile is obtained based on the temperature measurement results from 12 locations. .

  FIG. 6 is an in-furnace profile viewed from a cross section of the electric resistance furnace 11. FIG. 6 shows an in-furnace profile formed by connecting the A position, the B position, and the C position in the electrode ascending / descending direction at one place among the places where the thermocouples 23 are installed in the circumferential direction of the furnace. Although it should originally be shown for each location in the circumferential direction, the in-furnace profile in the depth direction at each of the 12 locations in the circumferential direction is displayed superimposed on one cross section for convenience. The curves indicated by T1 to T12 in FIG. 6 are in-furnace profiles corresponding to the respective twelve thermocouple installation positions in the circumferential direction.

  Accordingly, the first curve 51 in FIG. 5 is a curve formed by arranging the data at the position A shown in FIG. 6 in the circumferential direction and connecting the data. Similarly, the second curve 52 is obtained by arranging the data at the B position in FIG. 6 in the circumferential direction, and the third curve 53 is obtained by arranging the data at the C position in the circumferential direction. .

  The position of the electrode 5 in the furnace body is obtained by the graphic processing device 32. The estimation of the electrode position in the furnace can be performed as follows, for example. The dimensions, particularly the length, of the electrodes 5 are measured and input from the input unit 37 to the graphic processing unit 36. In addition, the amount of displacement of the electrode 5 relative to a reference position determined on the edge of the furnace body 4 is measured by the elevation measuring device 22 and input to the graphic processing unit 36. Based on the electrode length and the amount of displacement of the electrode 5 from the reference position, the position of the electrode 5, particularly the tip position of the electrode 5, can be estimated.

  Although the electrode tip is consumed during operation, the accuracy of estimation of the electrode position can be improved by performing the following correction, for example. The length of the electrode 5 is measured once a day. Since the amount of electrode consumption per charge of operation can be obtained from an empirical rule, a correction is made to subtract the amount of electrode consumption from the measured value for each charge. By inputting the correction value from the input unit 37 to the graphic processing unit 36, the estimated position of the electrode 5 can be corrected.

  Further, in the step of visualizing the position of the electrode 5 in the furnace body, the estimated position of the electrode 5 in the furnace body obtained by the graphic processing unit 36 is converted into image information and output from the graphic processing unit 36 to the display device 33. This is executed by making the image visible on the display device 33. The graphic processing device 32 can also graph only the in-furnace profile or the electrode position, or can collect and graph the in-furnace profile and the electrode position together.

  FIG. 7 is a diagram in which the in-furnace profile and the estimated position of the electrode are gathered into one figure. Based on the visualized in-furnace profile 20 and the position of the electrode 5 as shown in FIG. 7, the adjustment of the operation condition relating to the electrode 5, that is, the electrode 5 is displaced to a desired position in the ascending / descending direction, and the electrode is displaced at the displaced position. Energization is performed in between. Here, as a desired position, an arbitrary position can be selected based on the in-furnace profile 20, but in general, a position where the crust 8 protrudes most inward of the furnace body 4 is selected. Based on the visualized in-furnace profile 20 and the electrode position as shown in FIG. 7, that is, based on the visualized in-furnace situation, the estimated tip position of the electrode 5 can be accurately moved to a desired position. it can.

  FIG. 8 shows an example of a control flow when the electrode is displaced to a desired position. In step a1, the in-furnace profile is created by the in-furnace profile creation device 31 based on the temperature measurement result by the thermocouple 23. In step a2, the position of the electrode 5, especially the tip position, is obtained from the electrode dimensions given in advance and the measurement result of the lift measuring device 22. In step a3, the in-furnace profile and the electrode position are displayed as one image as shown in FIG. 7 by the graphic processing device 32 and the display device 33.

  In step a4, it is determined whether or not the electrode position is appropriate for the in-furnace profile. Here, the appropriate electrode position can be set, for example, when the tip of the electrode 5 is at a position where the crust 8 protrudes most inward of the furnace. If the electrode 5 is in an appropriate position, the operation proceeds to step a7 and the operation is continued. If the electrode 5 is not in the proper position, the process proceeds to step a5.

  In step a5, the positions of the three electrodes 5 are adjusted individually or collectively. Since the electrode position is forcibly displaced, the current and voltage are adjusted after the position adjustment. Thereafter, the process proceeds to step a6. In step a6, the position of the electrode is adjusted to check the in-furnace situation, and if necessary, an additional charging position and amount of coke as a reducing agent are determined and charged, and the operation proceeds to step a7 to continue the operation.

  The determination of electrode position suitability and electrode position control in steps a4 and a5 may be performed manually or automatically by a control device. That is, the operator may make a determination based on the in-furnace situation visualized, and the electrode lifting / lowering device 21 may be operated according to the determination result, and further includes a control device such as a microcomputer, The control device may control the operation of the electrode lifting device 21 in response to an input with the electrode position.

  Near the tip position of the electrode 5, the amount of resistance heat generation is the largest. Therefore, the crust 8 at that position is preferentially melted by moving the electrode tip position, for example, to the position where the crust 8 protrudes most inside the furnace and grows. Can be made. Therefore, it is possible to prevent the crust 8 from growing greatly toward the inside of the furnace, and it is possible to prevent the furnace volume from decreasing.

  The in-furnace profile shown in FIGS. 5 and 6 is a result of positively melting the crust 8 by displacing the tip position of the electrode 5 to a desired position based on the visualized in-furnace situation shown in FIG. It is obtained.

  Based on the in-furnace profile and electrode positions visualized as shown in FIGS. 5, 6, and 7, the operation conditions relating to the additional input of the raw material are adjusted. When the raw material is additionally charged, a position where the crust 8 does not grow so much inward of the furnace body 4 and the profile in the furnace is not narrowed is determined as a position suitable for additionally charging the raw material into the furnace body. An amount suitable for additionally charging the raw material into the furnace is determined according to the size of the furnace volume.

  By introducing an appropriate amount of raw material into a position where the in-furnace profile is not narrowed, the charged raw material can be smoothly dropped to a place where a large amount of resistance heat is generated by being energized at the tip of the electrode in the furnace. As the raw material falls into the furnace, preheating, drying, and preliminary reduction proceed with the flow of gas from the bottom of the furnace, so that the melting process is efficiently performed in a place where the resistance heat generation amount at the drop destination is large. By taking such an operation method, troubles such as shelf hanging and blowing up are prevented and the melting efficiency is improved, so that the processing capacity is improved and the power consumption can be improved.

  Further, when the in-furnace profile is located on the refractory material 3 side such as the stamp layer 45, the erosion of the refractory material 3 can be known. From this, by detecting abnormal wear of the refractory material 3 at an early stage and repairing the furnace wall after the hot water, operational troubles such as leakage can be prevented.

  As a result, troubles such as shelf hanging and blowing up during operation can be prevented as described above, and melting efficiency can be improved to improve the processing capacity and reduce the power consumption.

(Example)
Examples of the present invention will be described below. Here, the crust 8 is actively melted based on the visualized in-furnace profile and the estimated electrode position, which is the method of the present invention, and an appropriate amount is added to a position having a large in-furnace volume based on the visualized in-furnace profile. Example of operation in which the additional raw material was charged, and the operation of the electrode while raising and lowering the current were controlled, and a predetermined amount of additional raw material was charged at a predetermined position by imagining the state of the furnace from the appearance. The operation results are compared with an operation comparison example operated as described above.

  In both the operation examples and the operation comparison examples, the results of operation for 10 to 11 days were extracted, and the raw material processing amount, the power intensity, the metal component production amount, and the operation stability were evaluated.

  The amount of raw material treated is the weight of the amount of raw material that can be dissolved in the electric resistance furnace. The power consumption rate is the amount of power required to dissolve 1 ton of raw material. The metal component production amount represents the amount of the metal component that can be taken out from the raw material and used as a steelmaking auxiliary material by weight. Operational stability was evaluated based on the frequency of blowing up, which is one type of trouble that occurs during operation, and the stability of the electrode position during power-on and power-off.

  The larger the raw material throughput and the amount of metal component production, the better, and the lower the power unit, the better. About raw material processing amount and metal component production amount, it evaluated by the average value per day.

  Of the operational stability, the operational troubles were evaluated as ○ when no blow-up occurred, Δ when blow-up occurred but less frequently, and x when blow-up occurred frequently.

  Of the operational stability, the electrode positions at the time of power entry and at the time of power interruption were evaluated by the degree of variation of the electrode positions at the time of power interruption. Here, the time of power entry refers to a time when energization from the electrode is started to dissolve the next charge after the charge melting operation is finished. Moreover, the time of power stop means when a certain amount of metal component is dissolved in the furnace and the current supply is stopped to discharge the metal component melt from the tap hole.

  First, the result of having calculated | required the fluctuation | variation of the electrode position at the time of an incoming call and a power stop among operation stability is shown in FIG. 9 and FIG. FIG. 9 shows the electrode position of the operation example, and FIG. 10 shows the electrode position of the operation comparison example. In FIGS. 9 and 10, # 1, # 2, and # 3 represent the first, second, and third electrodes, respectively, the on represents the electrode position at the time of incoming, and the stop represents the electrode position at the time of stopping. To express. FIG. 9 and FIG. 10 show the results of obtaining the operating results for each of the three electrodes. Eight charges are dissolved per day, and the electrode position at the time of power entry is the position at the time of power entry at the first charge, and the electrode position at the time of power stop is the position at the time of power stop at the eighth charge.

  The electrode position at the time of power input does not vary greatly in either the operation example or the operation comparison example. This is due to the following reason. When a certain amount of metal component is melted in the furnace and discharged from the tap hole, the electrode is lowered to push out the molten metal to facilitate discharge, but the position where the electrode tip is lowered and stopped is the position of the tap hole. This is because it becomes almost constant.

  On the other hand, the variation in the position of each electrode at the time of stopping electricity is about 200 mm in the operation example, but exceeds 300 mm in the operation comparison example. This is due to the following reason. When melting of the raw material proceeds to some extent and molten slag is generated in the upper layer of the molten metal component, the electrode tip position is almost near the surface of the molten metal, and the molten slag or molten slag and molten metal component from the electrode Energize. When the crust is actively melted and melted while always maintaining a certain amount of furnace volume as in the operation example, the position of the hot water surface that has reached the required amount of tapping is changed every charge and every operation day. Therefore, the position of the electrode tip near the molten metal surface is less varied, and stable operation is realized. When power is applied regardless of crust growth as in the comparative operation example, the electrode position varies greatly depending on the degree of crust growth, and stable operation is hindered. In other words, when the crust grows and the furnace volume decreases, the molten metal level rises and the electrode position rises as the amount of molten metal increases, but the crust grows little and the furnace volume increases. In the case of not decreasing, even if the amount of the molten metal increases, the molten metal surface does not rise greatly, and the electrode position does not rise greatly.

  11 and 12 show the electrode positions shown in FIGS. 9 and 10 from different viewpoints. FIG. 11 and FIG. 12 represent the linear transition approximation of the transition of the electrode position at the time of power input and power stop with the passage of the operation days for each of the operation example and the operation comparison example. From FIG. 11 and FIG. 12, there is a tendency that the interval between the position when the electrode is turned on and the position when the power is stopped increases with the passage of the number of operating days. In addition, the interval between the electrode positions at the time of power-on and power-off at the end of the 11-day operation is larger in the operation comparison example than in the operation example. It changes to the shallower immersive position, indicating that the fluctuation of the electrode position is large.

  From this, it can be seen that in the operation example, the furnace volume for each operation day is substantially the same and stable, whereas in the operation comparison example, the furnace volume is not stable.

  Other evaluation results of the operation results are shown in Table 3 and Table 4.

  The operation example is about 8 tons / day greater in raw material throughput and about 4 tons / day in metal component production than the operation comparison examples. As a result, the power consumption rate is greatly improved in the operation example compared to the operation comparison example.

  Further, in the operation example, there is no blowing up or the occurrence frequency is low, whereas in the operation comparison example, there are three days in which the occurrence frequency is high in the operation for 10 days. It can be seen that is more excellent in operational stability than the comparative operation example. In the case of the operation example, since blowing up hardly occurs, the fact that heat loss is small also contributes to the improvement of the processing capacity.

  According to the operation method of the electric furnace of the present invention, it is clear that the melting efficiency is improved, the processing capacity is improved, the power consumption can be reduced, and the occurrence of the operation trouble is also prevented.

  As described above, in the present embodiment, the method of operating the electric resistance furnace in which the material to be melted is energized between the electrodes inserted into the furnace body is used for improving the melting efficiency of the steelmaking raw material. . However, the present invention is not limited to this. For the case of melting industrial waste, solidified slag, incinerated ash, etc. in electric resistance furnaces with different electrode types, etc., and in electric furnaces other than electric resistance furnaces. Can also be used effectively.

The structure of the electric furnace 10 used suitably for implementation of the operating method of this invention is simplified and shown. The position where the thermocouple 23 is provided in the circumferential direction in the furnace body is shown. The position where the thermocouple 23 is provided in the thickness direction of the refractory material 3 is shown. The method for obtaining the in-furnace profile in the in-furnace profile creation device 31 will be described. It is the in-furnace profile seen from the upper surface of the electric resistance furnace 11. It is the in-furnace profile seen from the cross section of the electric resistance furnace 11. The in-furnace profile and the estimated position of the electrode are gathered into a single figure. An example of the control flow at the time of displacing an electrode to a desired position is shown. The electrode position of the operation example is shown. The electrode position of the operation comparative example is shown. The electrode position of the operation example is shown. The electrode position of the operation comparative example is shown. The structure of the electric resistance furnace 1 used for melt | dissolution of a by-product is shown.

Explanation of symbols

1,11 Electric resistance furnace
DESCRIPTION OF SYMBOLS 3 Refractory material 4 Furnace body 5 Electrode 8 Crust 10 Electric furnace 12 Visualization device 21 Electrode raising / lowering device 22 Lifting / lowering measuring instrument 23 Thermocouple 31 In-furnace profile creation device 32 Graphic processing device 33 Display device

Claims (5)

An electric furnace operating method in which electricity is passed between a plurality of electrodes in a furnace to dissolve a material to be dissolved interposed between the electrodes,
Create an in-furnace profile by connecting the position of the temperature determined in advance as the melting temperature of the lump that is generated when the material to be melted adheres to the inner wall of the furnace body,
Visualize the furnace profile and electrode position,
An operation method of an electric furnace, characterized by adjusting an operation condition based on a visualized in-furnace profile and an electrode position.   The method of operating an electric furnace according to claim 1, wherein the adjustment of the operation condition is performed with respect to additional charging of the material to be melted into the furnace body.   The method of operating an electric furnace according to claim 1 or 2, wherein the adjustment of the operation condition is performed with respect to the electrode. At least some of the plurality of electrodes are provided to be relatively displaceable with respect to the furnace body,
4. The method of operating an electric furnace according to claim 3, wherein the adjustment of the operation condition relating to the electrode is performed by displacing the relatively displaceable electrode. The position of the temperature that is predetermined as the melting temperature of the mass,
A plurality of measurement points are distributed on the furnace wall of the furnace body, and a plurality of temperature sensors are provided in the thickness direction of the furnace wall at each measurement point to obtain the heat conductivity using a temperature detected. The operating method of the electric furnace as described in any one of Claims 1-4.

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