JP3512514B2 - Method for reducing deposits in electric smelting furnace - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to Zn, etc., which adheres to the furnace wall of an electric smelting furnace when a raw material mainly containing an oxide is dissolved and reduced, and a molten metal produced is refined to recover the metal. The present invention relates to a method of mainly reducing the amount of deposits.

[0002]

2. Description of the Related Art In a smelter where blast furnaces, electric furnaces, converters, etc. are in operation, a raw material pretreatment process, at the time of supplying raw materials into the smelting furnace,
A large amount of dust containing metal is generated during operation of the smelting furnace. In addition, in a factory equipped with a surface treatment line, a large amount of sludge is generated in the waste acid / waste liquid treatment process and the water recycling facility. It is known to use dust, sludge or the like as a charging raw material in an electric smelting furnace such as a resistance heating type electrode burying type electric furnace to melt an alloy. In order to operate this type of electric furnace under stable conditions, for example, Japanese Patent Publication No. 63-2
In Japanese Patent No. 5277, an insulating sleeve is attached to the outer circumference of the electrode to supply electric power in the furnace direction. In addition, JP-A-4-
In Japanese Patent No. 61053, the composition of molten oxide called karami is maintained within a certain range, and antimony oxide is reduced under stable conditions. Further, in Japanese Patent Publication No. 53-33937, rice husks are added to stabilize the unloading of the charging raw material and prevent the raw material from hanging.

[0003]

In an electric smelting furnace that produces a large amount of slag containing a large amount of steelmaking dust and waste acid sludge, fluctuations in the slag composition greatly affect the resistance in the furnace. As a result, when the electrode floats, the vicinity of the raw material inlet may be locally heated, and the raw material inlet may be narrowed due to seizure or deposition of deposits. If such a state continues, the distance from the electrode at the raw material inlet to the deposit (hereinafter,
It becomes difficult to supply the raw material because the pool width) becomes closer. Therefore, it is necessary to suspend the operation and open the furnace opening by poking to mechanically remove the deposits.
Remarkably reduces productivity. If the deteriorated furnace condition continues, the power supply to the melting area in the furnace will be insufficient. as a result,
The temperature in the furnace tends to decrease, and a compound having a high melting point, mainly Zn, gradually adheres to and deposits on the inner wall of the furnace. Therefore, the effective volume in the furnace becomes narrow, and the original production capacity of the electric smelting furnace cannot be exhibited. The present invention has been devised to solve such a problem, and controls an electric load according to the electrode position to operate an electric furnace with high productivity while suppressing deposits. With the goal.

[0004]

In order to achieve the object, the present invention provides a total of 40 steelmaking dust and waste acid sludge.
% In an electric smelting furnace for recovering Ni- and Cr-containing alloys by melting and reducing an oxide raw material containing at least 50% of the raw material.
m), the difference between the electrode tip position at the start of energization and at the end of energization is S
And the tip position of the electrode is 0.75 × H during energization.
The electric power load is adjusted so as to be as follows, and further, the electric power load is adjusted so that S ≦ 0.35 × H when the tip position of the electrode is 0.75 × H or less. In the electric furnace operation according to the present invention, the following actions are performed during operation:
It is preferable to repeat one or more times. -Under the condition that the tip position of the electrode can be maintained below 0.75 x H, the voltage between the furnace bottom and the electrode is 35 to 35 of the tap voltage.
Action to adjust the power load so that it becomes 45% Action to adjust the power load so that the amount of dust generation does not change with time Measure the electrical conductivity of the slag, and based on the measurement result, the electrical conductivity of the slag is 0 Action to supply raw material containing slag component so as to be 0.8 to 1.7 Ω ⁻¹ / cm Action to adjust external coke supply so that the basic unit of coke is 250 to 320 kg / ton-metal The operation method is suitable for an electric smelting furnace such as a blast furnace type electric furnace and a blast furnace type electric furnace, particularly for an electric furnace equipped with a Zedaberg type self-baking electrode. Further, it is effective when using a shaft type electric furnace in which tuyere for injection of powdery raw material is provided at the melting zone level on the side surface of the furnace body.

[0005]

[Operation] As the recycling rate of scrap generated in steelmaking plants increases, Z contained in dust and sludge increases.
The content of n and the like increases. The present invention is an operating method completed based on the knowledge obtained in the process of investigating the phenomenon that deposits increase in an electric smelting furnace using these as raw materials.
The cause of the increase in the deposits is that the electrode floats due to some change in the operating state, and the red-hot electrode causes the upper part of the raw material layer,
That is, it is mentioned that the raw materials near the furnace mouth, Zn volatilized and adhered, dust, and the like solidify strongly by heating, causing a hanging phenomenon. From this point, it is considered that the increase of deposits is suppressed when the floating of the electrode is suppressed by forcibly adjusting the position of the electrode by changing the power load. Further, by reducing the amount of dust that constitutes the adhered matter, the increase of the adhered matter is suppressed. On the other hand, it is speculated that the variation of the electrode is caused by the variation of the resistance inside the furnace due to the variation of the composition of the raw material. Therefore, by maintaining the supply amount of coke and the electrical conductivity of slag, which directly affect the resistance in the furnace, within appropriate ranges, fluctuations of the electrodes can be suppressed.

By systematically controlling these various factors, it is possible to prevent pool heating, increase in dust generation, destabilization of in-furnace resistance, etc. due to electrode levitation, which causes deposit formation, and prevent electric smelting. It becomes possible to suppress the adhesion and deposition of Zn, which tends to adhere to the inner wall of the furnace, and to efficiently process oxide raw materials such as dust and sludge. Hereinafter, the present invention will be specifically described together with its operation with reference to the flow chart of FIG. In the electric furnace operation according to the present invention, for example, as shown in FIG. 2, an electric smelting furnace constructed of a sidewall refractory 1 and a bottom refractory 2 is used. An electrode 3 is arranged in the furnace, and a raw material inlet 4 to a raw material 5 are provided between the electrode 3 and the furnace wall.
Is charged. The raw material 5 is resistance-heated, and the slag layer 6 and the metal 7 are produced. In addition, a coke bed 8 necessary for the reduction is provided above the metal 7. The refined metal is tapped from the tap hole 9 as appropriate. On the upper part of the furnace wall, a deposit 11 such as Zn easily deposits and accumulates, and a cooling facility 10 is provided to prevent the deposit from sticking. In such an electric smelting furnace, the boundary between the bottom of the metal layer 7 and the upper part of the furnace bottom refractory 2 is the furnace bottom, and the upper surface of the raw material 5 when charged to the maximum is the upper surface of the raw material layer. The depth H of the furnace is from the bottom of the furnace to the upper surface of the raw material layer.
The distance between the deposits 11 is the pool width W.

Regarding the position management of the electrode 3, the electrode immersion depth is set so as to be located at a height of 75% × H above the furnace bottom. When the tip of the electrode rises above the height of 75% × H, the heat conduction from the red-heated electrode portion of the electrode 3 itself, which is resistance-heated in the furnace, causes a portion of the upper portion of the raw material layer close to the electrode 3 The raw material 5 and the deposit 11 are heated and fused, and the hanging state is likely to occur. Further, the energization of the deposit 11 may heat and sinter the deposit 11 to form a strong crust that cannot be poked. The influence of the position of the electrode 3 on the deposit 11 and the like can also be seen from the fact that the temperature of the pool width W portion sharply rises when the electrode tip position becomes 75% × H or more as shown in FIG. Also, the pool width after the end of energization is becoming narrower when the electrode tip position becomes 75% × H or more. From this, it is understood that the tip position of the electrode needs to be 75% × H or less in order to prevent the increase of the deposit. 75% of the tip of electrode 3
When it exceeds the height position of × H, the power load is reduced as shown in the flow of FIG. In the case of current control, it is possible to deeply immerse the electrode 3 by lowering the tap voltage and lower the tip position of the electrode 3.

When the tip of the electrode 3 is lower than the height position of 75% × H, the stroke management of the electrode 3 is proceeded as a long-term management of the electrode position within one charge. The stroke S is the difference between the tip positions of the electrodes 3 at the start and end of energization. According to the investigations and studies by the present inventors, it has been found that stable operation with reduced deposits is possible when the stroke is 35% × H or less. In normal operation, the electrode 3 is at the lower limit position at the start of energization and at the upper limit position at the end of energization. When the energization time is T, the ascending speed of the electrode 3 is 0.
Ideally, it should be constant at a speed of 35 × H / T. This condition is to maintain the minimum power load required to improve productivity, to prevent the occurrence of arcs that reduce efficiency, and for the Zedaberg self-baking electrode, the firing process of the electrode paste (before reaching the melting or reaction zone). It is also the optimum condition for achieving the softening that occurs, heat conduction appropriate for the firing reaction, etc.).

When the stroke exceeds 35% × H, the ascending speed of the electrode 3 is 0.35 × H / T at some point during operation.
Get bigger. In this case, a rapid change is likely to occur in the furnace. Therefore, when it is estimated that the stroke is larger than 35% × H, the power load is reduced. As a method of estimating the stroke, for example, the fluctuation speed of the electrode 3 is calculated from the displacement of the electrode 3 and the energization time or the applied power until that time, and the target energization time of the operation or the target applied power is calculated based on the calculation result. There is a method of estimating the final displacement. When both the tip position and the stroke of the electrode 3 are within the proper range, the operating condition is maintained as it is, and the same control is repeated after a lapse of a certain time. In addition to controlling the electrode position, the voltage between the furnace bottom and the electrode (hereinafter referred to as the voltage between the furnace bottom) and the amount of dust generated are also managed, and the strength of the powdery granular material is increased to generate dust that causes deposits. Reduce the amount. Generally, when a powdery or granular raw material is produced, its strength is affected by the contents of volatile substances and water, the potency of the binder, etc., but most of it is determined by the particle size distribution of the raw material used. From the standpoint of high strength production, it is preferable that the particle size distribution of the raw material be appropriately wide. However, in the raw material targeted by the present invention, since there are many steelmaking dusts, waste acid sludges, etc., the particle size distribution is biased toward the finer side, and it is possible to make high strength pellets, briquettes, etc. Have difficulty.

Generally, the hot strength of the briquette can be improved by selecting a binder effective for improving the strength and using a high-performance brazing machine. However, when dust, sludge, or the like is used as a raw material, it is difficult to suppress the amount of dust generated only by improving the strength of the briquette because of economical or facility limitations. Therefore, the inventors of the present invention focused on the influence of the bottom-bottom voltage, which is one of the operating factors, on dust generation. FIG. 4 showing the relationship between the bottom-bottom voltage and the amount of dust generated.
As can be seen from the above, when the furnace bottom voltage is maintained within the range of 35 to 45% of the tap voltage, the dust generation amount can be suppressed. When the voltage between the furnace bottoms is less than 35% of the tap voltage, although the degree of dust formation does not change so much depending on the strength of the briquette, the power consumption rate rapidly deteriorates (increases). When the strength of the briquette is high, the furnace bottom voltage can be operated at a high voltage even within the range of 35 to 45% of the tap voltage, but when the strength is low, it is operated at an appropriately low voltage. In FIG. 4, the strength of the briquette increases in the order of A → B → C. Therefore, according to the strength of the briquette at that time, or according to the generation state of the deposits at that time, the tap voltage that can be applied to the maximum is adjusted so as not to reduce the productivity.

In any case, when the voltage between the furnace bottoms is 45% or more of the tap voltage, dusting is remarkable, which causes an increase in deposits, so that the power load is reduced. On the other hand, on the other hand, the actual amount of dust generated is managed, and if the amount of dust generated is increasing, the power load is reduced, and conversely, if the amount of dust generating is decreasing, the briquette is strong. When it is judged that there is a margin, the control to increase the power load is performed from the viewpoint of improving the capacity. The range of increase / decrease in power load is determined by the degree of deviation of various control values from the target range. Since this control is performed at regular time intervals, it is preferable to change the temperature as little as possible while observing the furnace condition so as to avoid a sudden change in the furnace condition. In the present invention, the electrical conductivity of the slag and the coke supply amount are controlled in order to prevent the unstable electrode position change and more effectively control the power load.

One of the substances constituting the deposit is metal or slag scattered from the inside of the furnace by blowing up. Therefore, when the abrupt fluctuation of the electrode that causes the blowing up is stabilized by optimizing the slag composition and the coke supply amount, the generation of deposits is suppressed. Regarding the electrical conductivity of the slag, the electrical conductivity of the slag is 0.
It is adjusted by supplying the slag component or the raw material containing the slag component so as to be 8 to 1.7 Ω ⁻¹ / cm. Under almost constant operating conditions, the relationship shown in FIG. 5 is established between the specific electric conductivity of slag, the furnace wall temperature, and the number of times of blowing. As is clear from FIG. 5, when the electric conductivity of the slag is maintained in the range of 0.8 to 1.7 Ω ⁻¹ / cm, the number of times of blowing up is reduced, the furnace wall temperature is low, and the deposit It can be seen that the generation of is suppressed.

When the electric conductivity of the slag is larger than 1.7 Ω ^-1 / cm, the electrode floats, and the hanging of the raw material is likely to occur. As a result, the raw material drops abnormally in the melting region, and blowing up is likely to occur. Further, in the latter stage of operation, not only it becomes difficult to set the electrode tip position to 75% × H or less as described above, but also the temperature inside the furnace decreases due to the decrease in resistance heating efficiency, making it difficult to maintain an effective inside volume. And reduce the power consumption rate. In such a case, the slag component B such as SiO ₂ or Al ₂ O ₃ is supplied so as to reduce the electric conductivity, in other words, increase the resistance. As a result, the resistance in the furnace increases, and in the case of current control, the electrodes are deeply immersed in order to maintain a constant current, so that the furnace condition is restored.

On the contrary, the electrical conductivity of the slag is 0.8 Ω ^-1 /
Below cm, it is necessary to dig deep into the electrode to maintain a constant power load. For this reason, the electrode is very close to the metal layer, and even a slight change in the furnace condition is likely to cause abnormal blow-up. In such cases, CaO,
The slag component A such as CaF ₂ is supplied to increase the electric conductivity of the slag. As a result, the resistance in the furnace is lowered, and in the case of current control, the electrode is appropriately floated to maintain a constant current, and the furnace condition is restored. The in-furnace resistance can also be controlled by the amount of coke supplied. In this case, the coke supply amount is controlled so that the basic unit of coke is 250 to 320 kg / ton-metal. Coke, which is a good conductive material, tends to lower the resistance of the furnace body when its amount increases, and tends to float the electrode. Further, when the amount of coke is small, the coke acts in the direction of increasing the resistance in the furnace and tends to immerse the electrode. Specifically, the increase / decrease in the supply amount of coke affects the electrode behavior as well as the electrical conductivity of the slag, as shown in FIG.

Coke is present in the furnace in an amount obtained by subtracting the amount consumed in the reduction reaction in the furnace from the amount supplied in the furnace.
When the amount of remaining coke is large, the resistance in the furnace is lowered and the electrode tends to float. Conversely, if the remaining amount is small,
The resistance in the furnace rises and the electrodes tend to sink. Therefore, the basic unit of coke is 250 to 320 kg.
When it goes out of the range of / ton-metal, the blowing frequency, the power efficiency, etc. are affected as in the case of the electric conductivity of the slag. Therefore, based on the coke basic unit calculated from the briquette internal coke amount and the external coke supply amount, the external coke supply amount is adjusted so that the coke basic unit is maintained in the range of 250 to 320 kg / ton-metal. Coke is supplied both internally and externally. In the exterior method, additional charging is performed according to the decrease in the level of the charged raw material, as seen in normal charging of raw materials. The coke used has various shapes such as powder, granules, and lumps, and the coke having the optimum shape is selected according to the characteristics of the furnace and the particle sizes of the main and auxiliary raw materials. In the interior method, a coke having an optimum amount and particle size is mixed with an oxide raw material together with a binder and kneaded, and then briquettes, pellets and the like are formed into an aggregate. The briquette, pellets and the like are subjected to heat treatment such as drying and sintering as necessary, or those having a certain degree of strength after a curing period of several days are used as the charging raw material.

Further, returning to the electric power load control here, when the electric power load is reduced, the supply of the slag component that reduces the amount of exterior coke and / or reduces the electrical conductivity is controlled. Then, when the electrical conductivity of the slag and the basic unit of coke are within the appropriate range, the process proceeds to electrode position management. That is, when the electric power load is reduced by the electric power load control, the furnace condition changes in the negative direction from the viewpoint of the productivity of the furnace.
In order to recover productivity, it is necessary to return to the original power load as much as possible. Therefore, the resistance in the furnace is increased by lowering the electrical conductivity of the slag and reducing the coke supply amount so that the electrode position does not deviate from the proper appropriate range even if it is increased again to the original power load. Therefore, even if the electrical conductivity of the slag and the unit of coke are adjusted, the result is as shown in Fig. 1.
As shown in FIG. 6, the electrode load control system is returned to, and the power load is controlled to optimize the electrode position. In this way, according to the present invention, a sudden change in the furnace condition such as electrode floating or blowing due to the instability of the resistance in the furnace that causes the generation of deposits is prevented, and as a result, overheating of the pool portion and dust The increase in the amount generated is suppressed.

Even with the above measures, the deposits may be generated and the electrodes may float. Therefore, as a final measure, for example, the sintering reaction is prevented in advance so that the deposit on the upper part of the raw material layer does not become a product that is difficult to remove even by poking. The most effective method is to use a cooling pipe or the like embedded in the furnace wall at the portion where the distance between the electrode 3 and the deposit 11 corresponding to the deposit fusion zone on the upper part of the raw material layer is the shortest, as shown in FIG. The cooling equipment 10 is provided. And
The temperature at which the deposit 11 begins to turn red (around 400 ° C),
Desirably, when the temperature approaches 350 ° C., the cooling equipment 10 is operated to prevent the sintering / solidification reaction. This facilitates mechanical removal of the deposit 11. Alternatively,
It is also possible to prevent the sintering reaction by spraying a cooling gas to a portion which is easily turned into red heat instead of the embedded cooling equipment 10. In this way, once the deposit 11 is removed and the inside of the furnace is expanded by poking,
A good condition is maintained in which adhesion and growth are difficult to proceed.

[0018]

【Example】

Example 1 (Charge No. 10 to 12) Electric furnace dust generated in a steelmaking factory producing various stainless steels, wet-collected converter dust, scales, etc. were dehydrated by a filter press and dried by an internal combustion kiln. . Further, scales generated by annealing pickling of the stainless steel strip and hydroxides collected by precipitation aggregation in the waste acid treatment step were similarly dehydrated and dried. Coke and a polymer flocculant were mixed with an oxide raw material containing about 60% of the total amount of steelmaking dust and waste acid sludge, and the mixture was kneaded and then briquetted. After curing the obtained briquette for several days, the briquettes were supplied to and melted in a Zedaberg-type electric smelting furnace equipped with a cooling facility at a raw material charging level. During energization, the fluctuation range of the electrode position per constant time is managed so that the tip position of the electrode does not rise beyond 0.75 × H and the amount of change from the start to the end of energization is 0.35. The electric power load was adjusted so that it was within × H. However, in the control in this case, the voltage between the bottoms of the furnaces was controlled at the same time, and further, the control of the electric power load by controlling the dust generation amount at intervals of 15 minutes was performed in parallel. That is, when the furnace bottom voltage exceeds 45% of the tap voltage, or when the dust generation amount tends to increase, the tap voltage is adjusted to be reduced. On the contrary, when the furnace bottom voltage is lower than 35% of the tap voltage or when the dust generation amount tends to decrease, the tap voltage is adjusted to increase.

FIG. 7 shows various operating conditions of charge No. 10.
Shown in. At 220 and 250 minutes after the start of energization, an electrode stroke of less than 0.35 × H was estimated, so the tap voltage was lowered. Moreover, since the voltage between the bottoms of the furnace reached 35% or less after 180 minutes, and the voltage between the bottoms of the furnace reached 45% or more after 210 minutes, the tap voltage was increased or decreased at each time. Furthermore, 23
Since the dust generation amount decreased at 0 minutes and the dust generation amount increased at 250 minutes, the tap voltage was increased or decreased at each time. Under these operating conditions, the operation continued for 3 charges. As a result, as shown in Table 2, with the charge No. 10 to 12, the amount of tapped metal was 8.3.
~ 8.6 tons / charge, pool width 350 ~ 390m
m, electric power consumption rate was 1090 to 1150 KWH / ton-raw material.

Example 2: (Charge Nos. 13 to 15) Basically, the same electric power load as in Example 1 was controlled for operation. However, the electrical conductivity of slag and the amount of coke supplied were also controlled at the same time. In controlling the electrical conductivity of the slag, the measurement probe is inserted into the slag layer in the furnace every 15 minutes to measure the electrical conductivity of the slag.
CaO or SiO ₂ was supplied so as to be in the range of 8 to 1.7 Ω ⁻¹ / cm. At this time, the difference between the target value and the measured value of the electric conductivity is converted into a difference in basicity, and the difference in basicity is calculated from the amount of slag in the furnace estimated at that time to CaO or S.
The supply amount was determined by converting the amount into iO ₂ . Then, the obtained supply amount of CaO or SiO ₂ was supplied to the pool width portion so that the supply rate was as uniform as possible in 15 minutes. In the control of the coke supply amount, the supply amount of the briquette containing the coke and the amount of the external coke supplied during the energization operation are managed, and the basic unit of the coke is constantly calculated. The basic unit of the coke is 250 to 320 kg / ton-metal The supply amount of exterior coke was determined so as to be within the range.

FIG. 8 shows an operating condition in which the electric conductivity of the slag and the coke supply amount are controlled simultaneously with the control of the electric power load.
Shown in. The electric conductivity was 1.7 Ω ⁻¹ / cm or more at 200 minutes after the start of energization, and became 0.2 at 265 minutes.
Since it became 8 Ω ⁻¹ / cm or less, the SiO ₂ -containing raw material was supplied so as to decrease the electric conductivity and the CaO-containing raw material was supplied so as to increase the electric conductivity at each time point. Under these operating conditions, the operation continued for 3 charges. As a result, as shown in Table 2, charge No. 13-
In No. 15, the tapping amount is 8.5 to 8.7 tons / charge, the pool width is 400 to 405 mm, and the power consumption rate is 1020 to 1020.
It was 1040 KWH / ton-raw material, and the amount of deposits was smaller than that in Example 1.

Example 3: (16-18) Basically, the same electric power load as in Example 2 was controlled, and the electric conductivity of the slag and the coke supply amount were also controlled to operate. However, in the third embodiment, when the command to reduce the electric power load is output, the amount of exterior coke is reduced and / or the component that reduces the electrical conductivity of the slag is controlled to be supplied. The operation status in this case is shown in FIG. At 190 minutes, 200 minutes, and 260 minutes after the start of energization, a rise in the bottom-bottom voltage, an increase in dust generation, and an increase in electrode stroke were observed, so the tap voltage was lowered. At that time, after the SiO ₂ -containing raw material was supplied and the coke supply amount was reduced, the tap voltage was increased again to maintain high productivity. In the third embodiment, the second embodiment
The electric load, the electrical conductivity of the slag, and the coke supply amount are controlled in the same manner as in, but the electric load is stable at a high level because the action to further reduce the in-furnace resistance is taken. Therefore, even if the resistance in the furnace rises and the electric power load is increased again, the floating of the electrodes and the increase of the dust generation amount are effectively suppressed. As a result, as shown in Table 2, the amount of tapping is 8.8 to 9.0 tons / charge, the pool width is 410 to 420 mm, and the power consumption rate is 990 to 1010.
KWH / tonne-raw material.

Comparative Example: (Charge No. 19 to 22) Coke and a polymer coagulant were mixed with the same oxide raw material as in Example, and the mixture was kneaded and then briquetted. The briquettes thus obtained were cured for several days and then fed into a Zedaberg type electric smelting furnace to be melted. During the operation, the operation was performed under the highest possible load condition without adjusting the external coke, the supply amount of the slag component, etc., according to the electrode immersion behavior. In Charge Nos. 19, 20, and 22, the tip position of the electrode is 75% × H or more on the steel plate. In Charge No. 21, the tip position of the electrode was maintained at 75% × H or less, but the fluctuation range of the electrode position was 35% × H or more.
Further, in the case of charge No. 23, the fluctuation range of the electrode position is 35
% × H or less, but the tip position of the electrode is 75% × H
Was exceeded. In each operation, record the electrode position during operation, and the distance between the wall and the electrode including the deposit after tapping,
That is, the pool width was measured, and the correspondence between the amount of tapping and the amount of tapping of the dissolution charge was recorded. The recording results of each example are shown in comparison with Table 1.

[0024]

[Table 1]

[0025]

[Table 2]

As shown in Table 1, in Examples 1 to 3, the tip position of the electrode was 75% × H or less, and the fluctuation range of the electrode was 35% × H or less. On the other hand, in the comparative example, either the tip position of the electrode or the fluctuation range exceeds the range specified in the present invention. It can be seen that the electrodes tend to float. As a result, compared with the comparative example, in Examples 1 to 3, the input electric power was effectively consumed for the melting of the raw material, etc., and as shown in Table 2, all show a high electric power consumption rate. In addition, Example 1
In Nos. 3 to 3, the floating of the electrode was prevented, so that the pool width was also prevented from widening. However, in the comparative example, the pool width gradually narrows due to the growth of the deposits, and it is difficult to immerse the tip end position of the electrode in an appropriate range. If this situation continues, the pool width will become narrower, and due to the adhesion of dust and the like and the resistance overheating of the pool part due to energization, hard deposits that cannot be removed will be generated, and the floating tendency of the electrode will become stronger. It becomes a state. In this case, finally, it is expected that an extremely bad operation state in which charging of raw materials is difficult is performed. Such deterioration of the furnace condition can be effectively solved by implementing the present invention as seen in Examples 1 to 3.

[0027]

As described above, in the present invention, by taking a stepwise and systematic action,
The most effective way is to prevent deposits from accumulating on the raw material inlet, and keep the distance between the electrode and the furnace wall wide at all times. Therefore, the unloading of the raw material into the furnace also progresses smoothly, and it is possible to centrally supply heat to the furnace by optimal immersion of the electrode, and the productivity is increased by reducing heat loss and expanding the furnace. . Further, even if an adhered substance is generated, it is prevented from changing to a strong one, so that it is possible to easily recover the ideal furnace condition by simple poking. In addition, the number of times of poking, which was frequently performed before the degree of adhesion becomes heavy as in the past, is remarkably reduced, and a decrease in work efficiency is prevented.

[Brief description of drawings]

FIG. 1 Control flow according to the present invention

[Fig. 2] Inside of electric smelting furnace

FIG. 3 Influence of tip position of electrode on pool width and temperature of pool width

[Fig. 4] Effect of bottom-bottom voltage on dust generation rate and power consumption rate

[Fig. 5] Effects of the specific conductivity of slag on the number of times of blowing and the temperature of the inner wall of the furnace

Fig. 6 Effect of coke intensity on the number of times of blowing and the temperature of the inner wall of the furnace

FIG. 7: Operation status of Charge No. 10 in Example 1

[Fig. 8] Operation status of Charge No. 13 in Example 2

[Fig. 9] Operation status of Charge No. 16 in Example 3

[Explanation of Codes] 1: Refractory on side wall 2: Refractory on bottom of furnace 3: Electrode
4: Raw material charging port 5: Raw material 6: Slag layer 7:
Metal 8: Coke bed 9: Iron tap 10: Cooling equipment 11: Adhesion H: Furnace depth W: Pool width

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-8-193212 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C21B 11/10 C22B 4/06 C22B 7 / 04

Claims (5)

(57) [Claims] 1. Steelmaking dust and waste acid sludge in total of 4
In an electric smelting furnace that dissolves and reduces an oxide raw material containing 0% or more to recover an alloy containing Ni and Cr, the depth of the furnace is set to H.
(Mm), where S is the difference between the electrode tip positions at the start of energization and at the end of energization, the tip position of the electrode is 0.75 during energization.
The power load is adjusted so that it is below × H, and when the tip position of the electrode is below 0.75 × H, S ≦ 0.35 × H
A method for reducing deposits in an electric smelting furnace, which comprises adjusting the electric power load so that 2. Under the condition that the tip position of the electrode can be maintained at 0.75 × H or less, further action is taken to adjust the power load so that the voltage between the furnace bottom and the electrode becomes 35 to 45% of the tap voltage. The method for reducing deposits in an electric smelting furnace according to claim 1, wherein the method is repeated once or a plurality of times during operation. 3. The method for reducing deposits in an electric smelting furnace according to claim 2, wherein the action of adjusting the electric power load is repeated at least once or a plurality of times during operation so that the amount of dust generation does not change with time. 4. The electrical conductivity of the slag is measured, and the electrical conductivity of the slag is 0.8 to 1.7 Ω ⁻¹ / c based on the measurement result.
The method for reducing deposits in an electric smelting furnace according to any one of claims 1 to 3, wherein the action of supplying the slag component-containing raw material so as to be m is repeated at least once or a plurality of times during operation. 5. Coke basic unit is 250 to 320 kg /
The method for reducing deposits in an electric smelting furnace according to any one of claims 1 to 3, wherein the action of adjusting the amount of external coke supply so as to obtain ton-metal is repeated at least once or a plurality of times during operation.