JPH06341773A - Operation stabilizing method for electric furnace - Google Patents

Abstract

PURPOSE:To provide a method for stabilizing an operation of an electric furnace which can stabilize the operation of the furnace by establishing a coke regulating reference and an electrode length estimation reference. CONSTITUTION:A moving trace of an end of an electrode under control of a position of the end of the electrode is sorted to a first pattern for reducing a rising speed of the electrode when an electric resistance value in an electric furnace is deviated from an upper limit of an optimum range of a predetermined electric resistance indicator, a second pattern for raising the rising speed of the electrode when it is deviated from a lower limit, and a third pattern for inhibiting alteration of the rising speed of the electrode when it falls within the optimum range, and a coke adding amount in the furnace is regulated and a depth of the electrode is estimated in response to the sorted electrode depth pattern and a state of a slag content of a component to be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stabilizing the operation of an electric furnace for the production of metals such as ferroalloys and alloys.

[0002]

2. Description of the Related Art FIG. 3 shows a state of refining operation using an electric furnace. Generally, the outer surface of a furnace wall 1 is constructed of chamotte refractory bricks and the inner surface thereof is carbonaceous refractory material. Has been built. The ore in the raw material A (ore and coke) charged from the raw material charging port 4 is stored in the electrode 2 (usually 3
It is melted by receiving resistance heat due to energization to (main use), and reduction refining proceeds in the mixed layer H of coke and semi-molten material, and the coke bed C, the mixed layer S of slag and coke S, and the molten metal M due to the difference in specific gravity. Divide. In the figure, 3 is a furnace lid, 5 is an exhaust gas duct, D is an adhering substance, and 10 is a tap hole which is opened periodically.

In such a construction, the heat quantity required for the electric furnace operation is the heat for melting the raw materials, Fe, M
It is given by the sum of the heat for reducing oxides such as n and Si, and the heat for giving fluidity to the molten metal or slag, and the required heat amount is supplied by the resistance heat generated near the tip of the electrode 2. . Specifically, coke is added to lump ore, sintered ore, pellets, etc., and the heat from the electrode 2 melts and reduces the ore. Then, the coke addition amount ratio to the added ore at this time was added to the electric furnace at a ratio to the added ore which seems to be appropriate according to past experience values.

[0004]

However, in the conventional electric furnace control method, since the ratio of the amount of coke added was determined depending on the past experience value, the change in the brand of the raw ore and the firing degree of the sintered ore. , The depth of the electrode (distance L2 from the tip of the electrode to the furnace bottom), the power load level, and the like, and the appropriate coke amount ratio for the production of ferroalloys, the following problems occurred.

That is, if the amount of coke added is insufficient or the electrode depth is deep, the metal yield is deteriorated due to insufficient reduction, the product is out of specification, and the electrode is consumed abnormally.
Problems such as erosion of electric furnace refractories (when the furnace was constructed with carbon bricks) were occurring. On the contrary, if the coke addition rate becomes excessive or the electrode depth becomes shallow, the power load decreases, the transformer trips due to the overcurrent, and the furnace blowing due to the rise of the electrode tip position. There were problems such as abnormal gas blowing from the tank), falling of shelves, and deterioration of slag fluidity due to excessive reduction.

At present, since a method for accurately determining whether the amount of coke in the electric furnace is excessive or insufficient before such a problem has occurred has not been realized, after the problem occurs, the proportion of coke added increases or decreases. There is no choice but to take measures and measure the electrode depth. As a result, the amount of coke added may be excessively increased or decreased, or other erroneous processing may be performed.As a result, the state of excess and deficiency in the amount of coke in the electric furnace may be repeated, and There was a problem that the proper amount could not be maintained.

For example, since the slag Mn% is 10% with respect to the target value of 15%, the coke addition amount is minus 2.
When tons were carried out, the slag Mn% might jump up to 18% after 3 days. The cause of this is that the electrode length was too long, 2830 mm, compared to the target value of 2450 mm, so that the slag Mn% was lowered, but it was mistakenly judged to be excessive coke and the coke reduction treatment was performed. Is returned to 2430 mm, which is close to the target value, and the slag Mn% has increased. The present invention takes into consideration the problems in the conventional electric furnace control method as described above, and establishes the coke adjustment treatment standard and the electrode length estimation standard, whereby the electric furnace operation can be stabilized. The purpose is to provide a method for stabilizing operations.

[0008]

According to the present invention, the amount of coke added in the electric furnace is adjusted according to the electrode depth pattern representing the movement trajectory of the electrode tip in controlling the electrode tip position and the state of the content of the reduced component. Is a method for stabilizing the operation of an electric furnace that adjusts the temperature and estimates the electrode depth.

The required amount of heat in the electric furnace operation is heat for melting the raw materials, heat for reducing the reducible oxides of Mn, Si, etc., and heat for imparting fluidity to the molten metal or slag. . These required heat amounts are supplied by electric resistance heat near the tips of the three electrodes. When the tip of the electrode is at the optimum position for the situation inside the furnace at that time, the heat that contributes to the requirements for melting the raw material, the reduction reaction, and improving the fluidity of the product is distributed in a well-balanced manner, and the power supply is maximized. It can be effectively utilized and a stable furnace operation state can be obtained.

Therefore, how to accurately control the position of the electrode tip according to the situation inside the furnace is the most important factor in improving the operating efficiency of the electric furnace. This is realized by the "electrode position control method for electric furnace" of JP 60-232477. Using the locus of the electrode position that appears when this electrode tip position control is performed (hereinafter referred to as the electrode depth pattern), the electric resistance value in the furnace, and the slag content rate of the components to be reduced, another Judging whether the amount of coke in the electric furnace is excessive or deficient, which is an important control item, the amount of coke added is increased / decreased, the depth of the electrode depth is estimated, or the electrode length (distance from the electrode tip to the holder) is adjusted. The estimation is performed.

That is, according to the present invention, the type of actual electrode depth pattern when the above-mentioned "electrode position control method for an electric furnace" is carried out is defined as "first pattern" in which the electrode depth of all three electrodes decreases from the middle. "A type, E type as a" third pattern "having one or more ascending-only electrodes, and" second pattern "in which the electrode depth increases abnormally
X type as. Using the classified electrode depth pattern and the slag content of the component to be reduced, the electrode length (or electrode depth) or excess or deficiency of the reducing agent is estimated, and the coke addition rate is adjusted. Is.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. The above-mentioned "electrode position control method of electric furnace" is a method of controlling the height position of the electrode tip during operation of the electric furnace, and the upper limit of the optimum range of the predetermined electric resistance index while measuring the electric resistance index. If it deviates from the above condition, the ascending speed of the electrode is reduced, and conversely, if it deviates from the lower limit, the ascending speed of the electrode is increased so that the electric resistance index is controlled to be maintained within the set range. To do.

FIG. 1 shows types of actual electrode depth patterns. As shown in the figure, the electrode depth L2 is A type in which the electrode depth decreases from the middle of all three electrodes, E type in which there is at least one electrode that only rises, and X type in which the electrode depth increases abnormally. Classified into.

[Example 1] A case where silicon manganese (SiMn) is manufactured using a closed electric furnace of 20,000 KVA (see FIG. 3) will be described below. Fig. 2 shows the moving average value of the basic unit of melting power of the actual furnace data and the type of electrode depth pattern. In the A type tap, the melting power intensity is becoming worse, or in many places, and in the E type tap, the melting power intensity is getting better or in many places. Further, in the X type, shelving has occurred. Table 1 shows the electric resistance value in the furnace and the CO content rate in the generated gas for each type of time unit.

[0015]

[Table 1]

As is clear from Table 1, in the A type, the electric resistance value in the furnace rises abruptly from the middle, and as a result, the electrode depth L2 is lowered. Even in actual operation, additional coke (+2 tons) is being implemented later. Further, in the X type, the electric resistance value in the furnace is low, the electrode suddenly rises, and the electrode operation is stopped midway. Even in actual operation, the amount of coke was reduced (-2 tons) after a delay. Furthermore, in the E type, the electric resistance value in the furnace is within the control range, the CO content rate in the generated gas is low, and the indirect reduction rate is high.

From these results, if the electrode depth pattern during operation can be controlled to the above-mentioned E type, stable coke operation becomes possible by adjusting the coke addition amount earlier, and reduction of shelves and melting can be achieved. It has become possible to further reduce the power consumption rate.

[Example 2] A case where silicon manganese (SiMn) was manufactured using a closed electric furnace of 20,000 KVA is shown.
According to the "electrode position control method for an electric furnace" disclosed in Japanese Patent Laid-Open No. 60-232477, the target value of each operation value when the electrode tip position control is performed is slag Mn: 12.5%, electrode depth pattern type : E type, electric resistance in electric furnace: 0.
33mΩ, coke addition rate 18%, electrode length L1: 2350
mm, electrode depth L2: 2200 mm. As the actual operation value, the slag Mn% was 10%, and only two of the three electrodes showed an X-type electrode depth pattern with an electric resistance value of 0.30 mΩ. Was estimated to be 2450 mm and the coke addition rate was reduced to 17.8%. After that, the slag Mn% approached the target value of 12.5%, and the electrode depth pattern type approached the E type.

[0019]

[Table 2]

The X type shown in FIG. 1 occurred when the electrode length L1 was longer than the target value.
That is, if the electrode length L1 is too long, the electrode tip is often buried in the molten metal in the furnace and the electric resistance value in the furnace becomes low. As a result of the control, the X type occurred. On the other hand, the A type, contrary to the X type, occurred when the electrode length L1 was shorter than the target value. That is, if the electrode length L1 is too short, the electrode tip cannot be embedded in the molten metal in the furnace so much that the electric resistance value in the furnace becomes high, and as a result of control, the A type occurs. Further, the E type is located between the X type and the A type, and therefore, the X type and the A type occur when they are biased too much to one side.

In the case of manganese ferroalloy, slag Mn (reduced component)% that represents the Mn value remaining without being reduced to metal Mn is an index for determining whether the amount of coke in the furnace is excessive or insufficient. That is, if the amount of coke in the furnace is insufficient, the reducibility deteriorates and the slag Mn% increases. If the amount of coke in the furnace is insufficient, the electric resistance value in the furnace will increase,
As a result of the control, the A type will occur. On the contrary, when the amount of coke in the furnace becomes excessive, the electric resistance value in the furnace becomes low, and as a result of the control, the X type occurs. By adjusting the amount of coke in the furnace and estimating the electrode length by using the slag Mn% value and the electrode depth pattern, the slag Mn% is controlled to an appropriate value and the required heat amount in the electric furnace operation is balanced. E that can be given well
The type can be maintained.

Table 2 shows a summary of these situations and operation actions. For example, if all electrodes are of X type (electrical resistance values are lower than the target value for all electrodes) and show a slab Mn% decrease tendency, it can be determined that there is an excessive tendency of coke in the furnace, and the capacity of the electric furnace And the operation of reducing the amount of coke added, which is determined by the type of ferroalloy.

If only a certain pole shows the X type (only the electric resistance value of a certain electrode is lower than the target value) and the slag Mn% shows a downward tendency, only the certain pole has an electrode length L.
1 is added to the determined value, and the operation is performed so as to estimate long (the electrode depth L2 is shallow).

Type A of electrode depth pattern for all electrodes
Appears (the electrical resistance value is higher than the target value for all electrodes) and the slab Mn% shows a downward trend, it can be determined that the coke is excessive, and it is determined by the capacity of the electric furnace and the type of ferroalloy. The amount of coke added is reduced and the electrode length L1 of all electrodes is estimated to be short (the electrode depth of all electrodes is deep) by subtracting the determined value.

When the electric resistance value of a certain electrode is higher than the target value, not all electrodes, it can be judged that the electrode length L1 of the electrode is shorter than the target value (the electrode depth is deep), and the electrode length The length L1 is subtracted from the determined value to estimate it to be short, and the coke addition amount determined by the capacity of the electric furnace and the type of ferroalloy is reduced. According to the stabilization method of the above-mentioned embodiment, the inside of the furnace can be stabilized, thereby eliminating the trip due to the furnace blowing, falling of the shelf, and overcurrent, and the electrode breakage can be reduced. Further, the consumption of electrodes and the consumption of raw materials can be made uniform. Standardization of operation can be achieved, which enables accurate electrode depth control (automation) and coke adjustment. It is possible to detect anomalies more quickly, which effectively adjusts the electrode length and the amount of coke added. The unit consumption can be improved, and the melting electric energy and electrodes can be effectively used. In addition, Mn slag loss can be reduced.

[0026]

As is apparent from the above description, according to the method for stabilizing the operation of the electric furnace of the present invention, it is possible to standardize the coke adjustment treatment standard and the electrode length estimation standard, which have been problems for many years. By doing so, various basic units can be greatly improved and stable electric furnace operation can be realized.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a result of an electrode depth pattern according to an embodiment of the present invention.

FIG. 2 is a basic unit of melting electric power and a depth pattern according to the embodiment.
It is a graph which shows a type.

FIG. 3 is a vertical cross section showing a configuration of an electric furnace of a conventional example.

[Explanation of symbols]

 1 Electric furnace wall 2 Electrode 3 Furnace lid 4 Raw material inlet 5 Exhaust gas duct A Raw material C Coke bed H Semi-molten layer S Slag M Metal L1 Electrode length L2 Electrode depth

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location F27B 3/28 7516-4K // H05B 3/00 340 7913-3K 350 7913-3K

Claims (3)

[Claims] 1. The coke addition amount in an electric furnace is adjusted and the electrode depth is estimated according to the electrode depth pattern representing the movement trajectory of the electrode tip in the control of the electrode tip position and the state of the content of the reduced component. A method for stabilizing the operation of an electric furnace. 2. The electrode depth pattern is a first pattern that lowers the ascending speed of the electrode when the in-furnace electric resistance value deviates from the upper limit of the optimum range of a predetermined electric resistance index, and deviates from the lower limit. The second pattern for increasing the ascending speed of the electrode in the case of the above, and the third pattern for not changing the ascending speed of the electrode when it is within the optimum range. Operation stabilization method. 3. The method of stabilizing operation according to claim 1, wherein the component to be reduced is slag, and the state of the content rate is any of a downward trend, a target value, and an upward trend.