JP2014141696A - Method of determining necessity of modification of operation conditions during converter blowing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of determining, reliably with better accuracy, necessity of modification of operation conditions by evaluating the state of the inside of the furnace, early by simple means, during converter blowing.SOLUTION: A method of determining the necessity of modification of operation conditions during converter blowing comprises counting the number Cf of occurrence times of the state in which the instantaneous value of the exhaust gas flow rate time change rate 'a', calculated by equation (1) every specified time in a specified period after desiliconization, deviates out of an acceptable range Bf and comparing the Cf with a threshold value Ccrit to determine the necessity of modification of operation conditions during the blowing operation. Bf and Ccrit are determined preliminarily from cases which are determined not to require modification of operation conditions during a blowing operation, according to the correlation between 'a' calculated by the equation (1) in a specified period after desiliconization and blowing indices during the blowing operation, on the basis of operation data of a plurality of the same-type blowing operations conducted in past. Equation (1): 'a'={Q(t+Δt)-Q(t)}/Δt, where Q is a flow rate of exhaust gas; t is a time; and Δt is a time interval.

Description

  The present invention relates to a method for evaluating whether or not it is necessary to change the operating conditions during the blowing operation by evaluating the reaction progress in the furnace in the initial stage of blowing in the blowing operation using a converter. .

  In order to obtain molten steel with a target quality (for example, P concentration) by blowing using a converter, it is necessary to appropriately control the blowing conditions. However, depending on the static operating conditions determined by the steel type and hot metal conditions at the start of blowing, the target quality (for example, P concentration) is not expected to be obtained, or the reaction state in the furnace is unpredictable (for example, the There is a possibility of occurrence of lapping). In such a case, it is necessary to stabilize quality and to stabilize blowing by performing dynamic control of changing (correcting) operating conditions during blowing.

  For this reason, many proposals have been made in the past as a method for evaluating the in-furnace condition during blowing and a method for controlling the blowing conditions based on the evaluation. For example, a method of continuously measuring the exhaust gas composition and flow rate during blowing, calculating the oxygen potential in the slag, the amount of accumulated oxygen, etc. by mass balance calculation, and resetting the blowing conditions based on it (for example, Patent Documents 1 and 2), a method of predicting the occurrence of slipping by a neural network or knowledge processing using the waveform state of the exhaust gas flow rate (see, for example, Patent Documents 3 and 4), an acoustic sensor or furnace pressure for measuring the exhaust gas flow rate A method of predicting the occurrence of slopping by combining sensors (for example, see Patent Document 5) has been proposed.

  However, the methods described in Patent Documents 1 and 2 require expensive gas analyzers to accurately measure the exhaust gas composition, and the maintenance load is large. The method needs to go through complicated processes for data processing, and the method described in Patent Document 5 has a large maintenance load on the acoustic sensor and the furnace pressure sensor, and both methods have problems in practicality. In other words, the actual situation is that there are almost no methods proposed in the past that have been put into practical use.

JP 2006-206930 A JP 2001-279317 A JP 2000-144229 A JP-A-5-222430 JP-A-6-279827

  Therefore, an object of the present invention is to more accurately determine whether or not it is necessary to evaluate the reaction state in the furnace at an early stage by simple means and to change the operating conditions during the blowing in the converter blowing operation. It is to provide a method capable of making a good and reliable determination.

The invention described in claim 1
In the dephosphorization blown operation or dephosphorization decarburization blown operation using a converter, the progress of the reaction in the furnace is evaluated by the fluctuation of the exhaust gas flow rate at the initial stage of the blown operation after the desiliconization, and during the blown operation A method for determining whether or not it is necessary to change operating conditions,
The exhaust gas flow rate time variation a defined by the following formula (1) is calculated at regular intervals during the predetermined period after the silicon removal, and the number of times Cf that the instantaneous value of the exhaust gas flow time variation a deviates from the allowable range Bf. Count
The number of times Cf is compared with a threshold Ccrit to determine whether or not the operation conditions need to be changed during the blowing operation.
The predetermined period after desiliconization is a period from the end of the desiliconization period to the time of a predetermined amount of acid sent that is 1/4 or less of the total amount of acid sent.
The allowable range Bf and the threshold value Ccrit are calculated in advance in the predetermined period after desiliconization based on operation data of a plurality of blowing operations performed in the past of the same type as the above (1 From the correlation between the exhaust gas flow rate time change degree a defined in) and the blowing index in the blowing operation, it is determined from those that do not require changing the operating conditions during the blowing operation.
This is a method for determining whether or not the operating conditions need to be changed during converter blowing.
a = {Q (t + Δt) −Q (t)} / Δt (1)
Here, Q: exhaust gas flow rate, t: time, Δt: time interval.

The invention described in claim 2
In comparison with the threshold value Ccrit, when the number of times Cf satisfies the conditional expression that defines the magnitude relationship between the number of times Cf and the threshold value Ccrit, the operation condition is determined during the blowing operation. 2. While determining that there is no need to change, when the number of times Cf does not satisfy the conditional expression, it is determined that the operation condition needs to be changed during the blowing operation. This is a method for determining whether or not to change the operating conditions during the converter blowing.

The invention according to claim 3
The blowing index is
It is one or more selected from the group consisting of phosphorus concentration after blowing, dephosphorization rate before and after blowing and occurrence of slopping during blowing.
It is a determination method of the necessity of change of the operating conditions during the converter blowing process of Claim 1 or 2.

  According to the present invention, since the progress of the reaction in the initial stage of blowing in the converter can be easily grasped using only the data of the exhaust gas flow rate measured by the existing exhaust gas flow meter, the simple means can be used at an early stage. The reaction status in the furnace was evaluated, and it became possible to determine more accurately and reliably whether or not the operating conditions need to be changed during the blowing. As a result, molten steel with the target quality can be obtained more stably while avoiding serious troubles such as occurrence of slopping during blowing.

It is a transition graph which shows typically the time variation of exhaust gas flow rate time variation degree a. It is a graph which shows the influence of (DELTA) t which has on the runout width (difference between the maximum value and the minimum value) of a at the time of non-blowing. 6 is a transition graph illustrating the change with time of a in Example 1. FIG. It is a figure for demonstrating typically how to obtain | require the candidate value Bi of the tolerance | permissible_range Bf, and the accumulation frequency Ci. 6 is a transition graph illustrating the relationship between Bi and Ci in Example 1. FIG. 4 is a graph illustrating the correlation between Ci and the post-treatment phosphorus concentration in Example 1. FIG. In Example 1, it is a graph showing the relationship between the correlation coefficient R ² illustrated in Bi and FIG. 10 is a transition graph illustrating the change with time of a in Example 2. FIG. In Example 2, Ci in the period from Ci and blowing after the start 4000 Nm ³ in the period from removal珪期end to a point oxygen-flow amount of the blow after the start 2000 Nm ³ up to the point of oxygen-flow amount of 6000 nm ³ ' It is a graph which illustrates the correlation with. FIG. 10 is a graph illustrating the relationship between Bi and the correlation coefficient R ² illustrated in FIG. 9 in Example 2. In Example 3, it is a transition graph which illustrates the time-dependent change of a. 6 is a graph illustrating the correlation between Ci and the dephosphorization rate in Example 3. FIG. In Example 3, it is a graph showing the relationship between the correlation coefficient R ² illustrated in Bi and 11.

  Hereinafter, the present invention will be described in more detail.

  According to the present invention, "in a blowing operation using a converter, whether or not it is necessary to evaluate the progress of the reaction in the furnace based on the fluctuation of the exhaust gas flow rate at the initial stage of blowing and to change the operating conditions during the blowing operation. The following is a prerequisite.

  That is, the “converter” targeted by the present invention is either a top blow converter or an top bottom converter, and does not cover a bottom blow converter. As will be described later, the present invention evaluates the superiority or inferiority of an oxidation reaction from molten iron to FeO (FeO formation reaction) by top blowing oxygen and a reduction reaction (CO gas generation reaction) by C in the molten iron. This is because it is a technical idea. In addition, the kind of bottom blowing stirring gas is not ask | required.

  In addition, the “blowing operation” targeted by the present invention is either a dephosphorization blowing operation or a dephosphorization decarburization blowing operation. In the decarburization blow smelting operation only for decarburization without dephosphorization, it is only necessary to actively promote the CO generation reaction, and it is necessary to consider the superiority or inferiority of the FeO formation reaction that contributes to the promotion of dephosphorization in the first place. This is because there is no need to apply the present invention.

  Further, in the present invention, “the initial stage of blowing”, which focuses on the fluctuation of the exhaust gas flow rate, is the period from the end of the desiliconization period to the time of a predetermined acid supply amount that is 1/4 or less of the total acid supply amount (hereinafter, "A predetermined period after desiliconization"). When blowing is started, the top blown oxygen is preferentially consumed for the oxidation of Si in the hot metal and Si in the Fe-Si alloy. Therefore, until the oxidation of Si is completed, the above FeO generation reaction is performed. And the contribution to the CO evolution reaction is small. Therefore, focusing on fluctuations in the exhaust gas flow rate is the period after the end of the desiliconization period. On the other hand, in order to obtain the target quality by changing the operating conditions during the blowing and to stabilize the subsequent blowing, it is necessary to evaluate the progress of the reaction in the furnace as soon as possible. The end point of “the initial stage of smelting” is at the latest, up to the time point of 1/4 of the total amount of acid sent. Since the end point of this “initial stage of blowing” varies depending on the type of blowing operation, an optimal time point (appropriately within the range up to the time of 1/4 of the total amount of acid feed predicted by static control ( What is necessary is just to select the time of a predetermined acid delivery amount.

The desiliconization period is defined by the amount of oxygen required until Si in the hot metal and Si in the Fe—Si alloy are oxidized to SiO _2. However, since the decarburization reaction occurs in the desiliconization period, Assume that 80% of the oxygen is consumed in the oxidation of Si. For example, when the concentration of Si in the hot metal is 0.3 mass% (hereinafter simply expressed as “%” for each chemical component) and the hot metal mass is 250 t, the desiliconization period is 750 Nm ³ (= 0.3 × 250 / 28 × 22.4 × 10 / 0.8).

  And, the present invention is based on the above premise that “a time change a of the exhaust gas flow rate a is calculated every predetermined time in the predetermined period after the desiliconization, and an instantaneous value of the exhaust gas flow rate time change a is within an allowable range. The number of times Cf that deviates from Bf is counted, and the number of times Cf is compared with a threshold value Ccrit to determine whether or not the operating conditions need to be changed during the blowing operation.

  Here, when blowing is started in the converter, the top-blown oxygen is preferentially consumed for the oxidation (desiliconization reaction) of Si in the hot metal and Si in the charged Fe—Si alloy. When the oxidation (desiliconization reaction) of Si is completed, the molten iron oxidation reaction (FeO formation reaction) by the blown oxygen represented by the following formula (2) and the molten slag by C in the molten iron represented by the following formula (3) The reduction reaction (CO generation reaction) of intermediate iron oxide is started, and both reactions proceed simultaneously.

Fe + (1/2) O ₂ (g) → FeO (2)
FeO + C → Fe + CO (g) (3)

  During blowing after the desiliconization period, oxygen consumption is controlled by either FeO generation or CO generation in the entire system, depending on which of the above two reactions occurs preferentially. Is determined.

  The FeO production reaction represented by the above formula (2) is a reaction in which the gas decreases, while the CO generation reaction represented by the above formula (3) is a reaction in which the gas increases. Therefore, by paying attention to the fluctuation of the exhaust gas flow rate, it can be estimated which reaction of the above formulas (2) and (3) occurs preferentially in the furnace.

  When the operating conditions such as the oxygen flow rate and the bottom blowing stirring gas flow rate are not changed during the blowing, both of the above reactions are eventually balanced and become a steady state. Judgment of the conventional blowing status based on the exhaust gas flow rate is made after the above two reactions are balanced and reach a steady state, so the timing of the judgment is delayed, and even if the operating conditions are subsequently changed, the target is set. There were problems such as inability to obtain molten steel quality and prevention of deterioration of blowing conditions due to slopping.

  Therefore, in order to grasp as soon as possible a sign of which of the two reactions is preferential (dominant), as a parameter, the degree of time variation of the exhaust gas flow rate defined by the following re-expression (1) (below) , Also referred to as “exhaust gas flow rate change rate.”) A was adopted.

a = {Q (t + Δt) −Q (t)} / Δt (reprinted formula (1))
Here, Q: exhaust gas flow rate, t: time, Δt: time interval.

  Conceptually, in the case of a> 0, the exhaust gas flow rate tends to increase, and this indicates a sign that the generation of CO gas represented by the above formula (3) is preferential (dominant). On the other hand, in the case of a <0, the exhaust gas flow rate tends to decrease, indicating that the FeO generation represented by the above formula (2) becomes preferential (dominant). When a = 0, the exhaust gas flow rate tends to stabilize, and the generation of FeO expressed by the above formula (2) and the generation of CO gas expressed by the formula (3) are balanced, and the steady state Showing signs of becoming.

  The reason of expressing the above as conceptual is that during the actual operation, even if the reaction of the above formula (2) is preferential, the reaction of the above formula (3) always occurs, and a is a constant amplitude. The hunting behavior of reciprocating + and-values is shown in (absolute value of a).

  In blowing using a converter, since the C concentration in the hot metal is high at the initial stage of blowing, the reaction of generating CO gas is likely to occur preferentially. For this reason, once the CO gas generation reaches a preferential steady state, the generation of FeO tends to hardly occur.

  That is, in order to control in order to promote the generation of FeO, the sign that the generation of CO gas is preferential must be small, and therefore the absolute value (amplitude) of a needs to be controlled to be small (a When the absolute value of is large, the negative value of a is large, and the priority of the reaction of the above formula (3) is large).

  From the above, the appropriate value (range) of a differs for each target reaction, particularly for each degree of priority of the FeO production reaction.

  In the case of dephosphorization blowing and dephosphorization decarburization blowing targeted by the present invention, in order to promote dephosphorization, FeO generation that promotes dissolution of CaO is important. Must be prioritized. That is, the absolute value of a is required to be small (the swing width is small).

  On the other hand, in the case of decarburization blowing which is not the subject of the present invention, it is necessary to promote the generation of CO gas represented by the above formula (3). That is, the absolute value of a may be large (the swing width may be large).

  It is desirable that the timing for catching the indication that the target reaction is preferential is as early as possible after the start of blowing. However, as described above, in the desiliconization period immediately after the start of blowing, since the top blown oxygen is consumed for the oxidation of Si, the contribution to the two reactions of FeO generation reaction and CO gas generation reaction is small. Therefore, the priority of the two reactions is important after the desiliconization period.

  Therefore, the timing for evaluating the priority of both reactions is after the desiliconization period, but the earlier the better. Therefore, in order to determine whether or not the priority of both the above-mentioned reactions of interest is shifting to a steady state, the determination was made by accumulating the number of times indicating a change in priority.

  As described above, a takes positive (+) and negative (-) values, but in the present invention, focusing on the absolute value, specifically, the blowing condition is determined only by the positive (+) value. To do.

  In the present invention, blowing is performed by comparing the cumulative number of times Cf in which the time change degree a of the exhaust gas flow rate deviates from a predetermined allowable range Bf from the end of the desiliconization period to a predetermined time and the threshold value Ccrit. The situation (reaction progress) was evaluated and it was decided whether or not it was necessary to change the operating conditions during the blowing. In addition, instead of the cumulative number of times Cf outside the allowable range Bf, evaluation may be made based on a similar concept such as an accumulated time outside the allowable range Bf.

  “The permissible range Bf and the threshold value Ccrit are preliminarily determined based on the operation data of a plurality of blowing operations performed in the past of the same type as described above, and the exhaust gas flow rate time variation a calculated in the predetermined period after the desiliconization. And the correlation with the blowing index in the blowing operation can be determined from those that do not require changing the operating conditions during the blowing operation.

  More specifically, for example, the current blowing operation (for example, dephosphorizing blowing) to which the present invention is applied is the same type of blowing operation (dephosphorizing blowing), and a plurality of charges that have been performed in the past. Using the operation data, for each charge, the relationship between the exhaust gas flow rate time variation a and the blowing index is investigated from the end of the desiliconization period to a predetermined time later. Blowing indicators include phosphorus concentration after blowing (also referred to as “phosphorus concentration after treatment”), dephosphorization rate before and after blowing, and the state of occurrence of slopping (scale and frequency) during smelting. However, these indicators may be used alone or in combination of two or more.

  And, from the correlation between the exhaust gas flow rate time variation degree a and the blowing index obtained by consolidating the relationship between the exhaust gas flow rate time variation degree a and the blowing index investigated for each charge with respect to the plurality of charges. The allowable range Bf and the threshold value Ccrit are determined.

  And in the current blowing operation to which the present invention is to be applied, the exhaust gas flow rate time change degree a is calculated from the end of the desiliconization period to the time after the predetermined time, and the number of times outside the allowable range Bf is integrated, The cumulative number Cf is compared with the threshold value Ccrit, and it is determined whether or not the operation condition is changed during the blowing by the magnitude.

  For example, when the cumulative number Cf is equal to or less than the threshold value Ccrit, the operation is continued without changing the operation condition. On the other hand, when the cumulative number of times Cf exceeds the threshold value Ccrit, it is determined that if the current operating conditions are continued, the intended quality of the molten iron or molten steel cannot be obtained. It is determined that the (condition) needs to be changed.

  The change in the above operating conditions (blowing conditions) means, for example, changing the stirring force by changing the top blowing condition or the bottom blowing condition.

  That is, when the fluctuation range of the exhaust gas flow rate time variation a is small and the cumulative number of times Cf outside the allowable range Bf is below the threshold value Ccrit, the FeO generation reaction (the above formula (2)) is preferential. Since it is in the excessive formation state, it is necessary to promote the reduction reaction of FeO by hot metal C (the above formula (3)), and it is necessary to strengthen the stirring force. Examples of means for enhancing the stirring force include an increase in the amount of top blowing oxygen, a lowering of the top blowing lance, and an increase in the bottom blowing flow rate.

  On the other hand, when the fluctuation range of the exhaust gas flow rate variation degree a is large and the cumulative number of times Cf outside the allowable range Bf exceeds the threshold value Ccrit, the CO gas generation reaction (the above formula (3)) is preferential. Since the hatching is in a poor state, it is necessary to suppress the FeO reduction reaction by the hot metal C (the above formula (3)), and it is necessary to weaken the stirring force. Examples of means for weakening the stirring force include a reduction in the amount of top blowing oxygen, an increase in the top blowing lance, and a reduction in the bottom blowing flow rate.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

  Various blowing operations were carried out in the top-bottom blowing converter under the equipment specifications and basic operating conditions shown below.

・ Top-bottom blowing converter Capacity: 250ton
MgO-C refractory, top blowing lance Nozzle number: 6 holes Nozzle outlet diameter: 55 mm
Nozzle tilt angle: 15 °
Blowing oxygen flow rate: 0.6 to 3.4 Nm ³ / min / ton
・ Bottom blow Nozzle number: 4 holes Gas type: N ₂ , Ar, CO
Bottom blowing gas flow rate: 0.02-0.09 Nm ³ / min / ton
-Auxiliary raw material Quick lime was used as a CaO source.
The SiO ₂ source is Si, Fe—Si alloy, and silica in hot metal.
Note that the Fe—Si alloy was used as a heat raising agent.
Silica was used as a slag basicity adjuster.
Light-burned dolomite was used for the purpose of protecting refractories.
Temperature control, mill scale and iron ore were used as iron sources.

[Example 1] Dephosphorization blow smelting operation With regard to a plurality of charges of dephosphorization blown performed with the target post-treatment phosphorus concentration (phosphorus concentration after blown) being 0.03% or less, the data of the exhaust gas flow rate are used. Then, the reaction state in the furnace at each charge was evaluated, and an attempt was made to determine whether or not the operating conditions had to be changed in order to achieve the target post-treatment phosphorus concentration.

  The operating conditions of dephosphorization blowing in this example are as follows.

-Hot metal conditions Charge: 260-280ton
Hot metal components before blowing:
C = 4%
Si = 0.2-0.5%
P = 0.10-0.16%
Hot metal components after blowing:
C = 3.5-4%
P = 0.02-0.05%
-Top blowing condition Desiliconization period (Maximum acid feed amount 1500 Nm ³ from the start of blowing): ε _T = 1 to 5 kW / ton
Dephosphorization period (after desiliconization period): ε _T = 0.04 to 0.2 kW / ton
・ Bottom blowing condition ε _B = 0.6 to 1.5 kW / ton

Here, epsilon _T is Kai et al. (Iron and Steel, 68 (1982), 1946) is defined by the following equation proposed by (4), a stirring power density due to the top-blown oxygen.

Ε _B is the stirring power density by the bottom blowing gas defined by the following formula (5) proposed by Mori et al. (Iron and Steel, 67 (1981), 672).

  In each charge, the exhaust gas flow rate time variation a was calculated by the above formula (1) using the data of the exhaust gas flow rate Q (t) measured at a predetermined sampling interval (1 s in this example) during blowing. . The exhaust gas flow rate was measured using a venturi flow meter. When the calculated a is plotted against time t, time variation is shown as schematically shown in FIG.

  In determining the time interval Δt in the above formula (1), at the time of non-blowing, Δt is sequentially changed to calculate a, and the reactions of the above formulas (2) and (3) are involved. Δt was determined after confirming the effect of Δt on the deflection width of “a” in a state in which it was not.

  FIG. 2 shows the effect of Δt on the amplitude of a (the difference between the maximum value and the minimum value) during non-blowing. As can be seen from this figure, the fluctuation width of a tends to increase as Δt decreases. In other words, even a slight fluctuation in the exhaust gas flow rate is regarded as a sign of a change in a, and thus the sensitivity is considered to be high. However, there is a concern that the sensitivity becomes too high and it may be excessively determined that the operation change is necessary. . On the other hand, if Δt is increased too much, the swing width of a decreases, and there is a concern that the sensitivity of capturing signs of a change during blowing is reduced. Further, it shows a tendency that the influence of Δt on the change of the swing width of “a” becomes small around Δt = 5 s. From the above, in this embodiment, Δt = 5 s.

  FIG. 3 shows an example of a change with time of a for each of the charge whose post-treatment phosphorus concentration has reached the target phosphorus concentration (0.030% or less) and the charge that has not reached the target phosphorus concentration.

  As shown in FIG. 3, the time variation of “a” shows almost the same behavior from the end of the desiliconization period to 400 seconds, which is about ½ of the entire blowing. Since the secondary raw materials such as iron ore are charged in the middle of the blowing, the behavior of a rapidly changes due to disturbance factors due to the addition of the secondary raw materials. Therefore, it is desirable to grasp (evaluate) the blowing condition in the early stage of blowing with few disturbance factors. In this example, the blowing condition was evaluated at 200 seconds, which is about ¼ of the entire blowing. As described above, a in the period from the end of the silicon removal period to the time of 200 s after the start of blowing (a predetermined period after the silicon removal) was used.

  As a result of calculating a for a plurality of charges, the value of a in the period from the end of the desiliconization period to the time of 200 s after the start of blowing is as shown in FIG. In the charge that did not reach, a timing indicating a value out of the range of “−20” to “20” was recognized, but it changed within the range of “−20” to “20”. On the other hand, as shown in FIG. 3A, the value of “a” during the same period changed within the range of “−4” to “4” in the charge in which the post-treatment phosphorus concentration reached the target phosphorus concentration.

  Therefore, in this example, it was determined that it was effective to set an allowable range Bf that does not require changing the operating conditions during the blowing, between “4” and “20” as the absolute value of the amplitude of a. .

  From the above, in order to determine Bf, a value in increments of “1” between “4” and “20” is taken as a candidate value Bi (i = 1, 2,..., 17) of Bf. As schematically shown, in each Bi (i = 1, 2,..., N), the cumulative number of times Ci (i = 1, 2,... 17) was obtained. FIG. 5 shows an example when a value of “15” is adopted as Bi for the period from the end of the silicon removal period in FIG. 3 to the time of 200 s after the start of blowing. As shown in the figure, Ci = 2 for the charge in which the processed phosphorus concentration reached the target phosphorus concentration in (a), and Ci = 15 for the charge in which the processed phosphorus concentration in (b) did not reach the target phosphorus concentration. It is. And the correlation between this Ci and the post-treatment phosphorus concentration which is one of the blowing indices was investigated.

FIG. 6 exemplifies the result of investigating the correlation between Ci and the post-treatment phosphorus concentration by linear regression and obtaining the correlation coefficient when Bi = 11, 15, and 20. FIG. 7 shows the relationship between the correlation coefficient R ² obtained in this way and the candidate value Bi. As shown in the figure, the candidate value Bi correlation coefficient R ² between the "13" - "18" is maximized. In this embodiment, “15” is adopted as Bf. In addition, as a result of comparing the relationship between the candidate value Bi and the correlation coefficient R ² for each of 200 s and 300 s from the end of the desiliconization period, it was confirmed that there was no significant difference between the two. For this reason, as described above, 200 s, which is an earlier timing, is employed in this embodiment.

  Since “15” is adopted as Bf, the threshold value of the cumulative number of times Cf that satisfies the target post-processing phosphorus concentration of 0.030% or less using FIG. 6B where the candidate value Bi is “15”. Ccrit was determined to be “4”.

  That is, if the cumulative number Cf> Ccrit = 4 in which a exceeds Bf from the end of the desiliconization period to 200 s after the start of blowing, if the blowing is continued under that condition, the post-treatment phosphorus concentration will be 0. It can be seen that the probability (possibility) of exceeding 03% is high. In other words, it is necessary to change the blowing conditions when Cf> Ccrit = 4 (that is, when Cf = 5 is reached) in order to obtain the target post-treatment phosphorus concentration of 0.030% or less. It is possible to determine that there is.

  For 6 charges of dephosphorization blowing shown in Table 1 below, using Bf = 15 and Ccrit = 4 determined as described above, an attempt was made to determine whether the operating conditions had to be changed during blowing. It was.

  As shown in the table, charge no. A1 to A3, since the cumulative number of times Cf where a exceeds Bf at the time of 200 s from the end of the desiliconization period to the start of blowing does not exceed Ccrit = 4, it is necessary to change the operating conditions during the blowing. It is determined that there is no. These charges do not change the operating conditions during blowing even in actual operation, but the P concentration after blowing (after treatment) achieves the target of 0.030% or less.

  On the other hand, charge no. In A4 to A6, since the cumulative number of times Cf in which a exceeds Bf at the time of 200 s after the desiliconization period ends and after the start of blowing, Cfrit exceeds 4, it is necessary to change the operating conditions during the blowing. It is determined that there is. However, in actual operation, since the operation conditions are not changed during blowing, the P concentration after blowing (after treatment) cannot achieve the target of 0.030% or less.

  From this, if the present invention is applied in dephosphorization blow smelting operation, it is possible to easily and accurately determine whether or not the operating conditions need to be changed early during blowing, and stably produce hot metal having a target P concentration after treatment. It was confirmed that it was possible.

[Example 2] Dephosphorization and decarburization blowing operation (general dredging, low carbon steel blowing)
For multiple charges of dephosphorization and decarburization blowing of general dredging, using the exhaust gas data, the reaction conditions in the furnace at each charge are evaluated, and in order to avoid the “sloping large” defined below, An attempt was made to determine if a change was necessary.

  Here, slopping refers to a phenomenon in which molten slag is ejected from the furnace outlet. This is an operation-specific phenomenon because it is affected by the capacity of the converter vessel, the amount of hot metal and auxiliary materials charged in the converter. In this specification, a large amount of molten slag is ejected to the outside of the furnace and it is difficult to continue the operation as it is, “sloping is large”, although the occurrence of slopping is seen, the state where the operation can be continued Was defined as “no slopping”, and “no slopping” as a state where no slopping occurred.

  The operating conditions of dephosphorization and decarburization blowing of general soot in this example are as follows.

-Hot metal conditions Charge: 260-290ton
Hot metal components before blowing:
C = 4%
Si = 0.2-0.5%
P = 0.09-0.16%
Molten steel composition after blowing:
C = 0.001 to 0.4%
P = 0.005 to 0.03%
・ Top blowing condition ε _T = 2 to 5 kW / ton
・ Bottom blowing condition ε _B = 0.2 to 0.3 kW / ton

Here, the definitions of ε _T and ε _B are the same as those in the first embodiment.

  Further, as in Example 1, the sampling interval of the exhaust gas flow rate was 1 s and Δt = 5 s.

  In the dephosphorization blowing of Example 1 above, achieving the target post-treatment phosphorus concentration is the highest priority, whereas in the general phosphorus dephosphorization decarburization of this example, the suppression of slopping is the highest priority. It is.

  FIG. 8 shows an example of each change of a with respect to each of the charge that has reached “large slipping” and the charge that has remained “small slipping” during blowing.

  Here, in the slopping, FeO produced excessively in the early stage of blowing is reduced by hot metal C in the middle of blowing, and as a result, the generated CO gas fills the molten slag, and at a certain timing, the CO gas rapidly increases. It refers to a bumping phenomenon in which molten slag escapes from the molten slag and the molten slag in the furnace is ejected outside the furnace.

  That is, it is considered that the slopping is mainly caused by excessive FeO generation in the early stage of blowing. That is, for the prediction of slopping, it is important to grasp the excessive FeO production in the initial stage of blowing.

Further, in FIG. 8 (a), the exhaust gas flow rate time variation a is rapidly increasing, reaching the “sloping large” in the vicinity of the blowing time 5 min (= 300 s), in order to avoid the “sloping large”. Therefore, it is necessary to determine whether it is necessary to change the operating conditions at an earlier stage. Therefore, in this embodiment, it was decided to evaluate the blowing conditions at the time of the oxygen-flow amount 2000 Nm ³ corresponding to about 1/2 of the time of blowing time 5min that led to "slopping large".

In the same manner as in Example 1, the results of calculating the a plurality charge, de珪期period from the end to the point of oxygen-flow amount of the blow after the start 2000 Nm ³ of a in (de珪後predetermined period) value As shown in FIG. 8 (b), in the charge staying in “sloping small”, a timing indicating a value out of the range of “−9” to “9” was recognized, but almost “−9”. It moved within the range of ~ 9. On the other hand, as shown in FIG. 8A, the value of “a” during the same period was almost in the range of “−1” to “1” in the charge that reached “large slipping”.

  Therefore, in this example, it was determined that it is effective to set an allowable range Bf that does not require changing the operating conditions during the blowing, between “1” and “9” as the absolute value of the amplitude of a. .

  From the above, in order to determine Bf, a value in increments of “1” between “1” to “9” is taken as a candidate value Bi of Bf, and as schematically shown in FIG. The cumulative number of times Ci was obtained by integrating the number of times that exceeded the value of Bi.

Here, as an index for evaluating the magnitude of slopping, in this example, the cumulative number Ci ′ in which the value of a exceeds Bi in the period from 4000 Nm ³ to 6000 Nm ³ was used. In other words, when slopping occurs, the exhaust gas flow rate increases due to the generation of CO gas, so a increases, and the cumulative number Ci ′ increases. Therefore, Ci ′ is used as an index for evaluating the occurrence of slopping. In addition, as illustrated in FIG. 8A above, the time to reach “large slopping” is the middle stage of blowing, and in this example, the total amount of acid sent is over 10,000 Nm ³ , so that the slopping is evaluated. The middle stage of blowing as a period was set so that the amount of acid sent was 4000 Nm ³ to 6000 Nm ³ .

9, transmission and Ci in the period (de珪後predetermined period) up to the time of the oxygen-flow amount of the blow after the start 2000 Nm ³ from the de-珪期end in FIG. 8, the blow after the start 4000 Nm ³ of 6000 nm ³ An example in which values of “4”, “7”, and “9” are employed as Bi for the results of investigating the correlation with Ci ′ in the period up to the time point of the acid amount is shown.

The correlation coefficient R ² determine the correlation between Ci and Ci 'in each Bi and linear regression correlation coefficient R ² determined in this way, in FIG. 10 shows the relationship between the candidate value Bi It was. As shown in the figure, the candidate value Bi correlation coefficient R ² between the "6" to "8" is maximized. In this embodiment, “7” is adopted as Bf.

  Since “7” is adopted as Bf, the threshold value Ccrit of the cumulative number of times Cf that does not result in “large slopping” is set to “11” using FIG. 9B where the candidate value Bi is “7”. Decided.

That is, when a is a cumulative number Cf <Ccrit = 11 which exceeds the Bf in oxygen-flow amount of time of blowing start after 2000 Nm ³ from the de-珪期end (de珪後predetermined period), blown in the condition It can be seen that if the smelting is continued, there is a high probability (possibility) of reaching “large slopping” in the middle of blowing. In other words, in order to avoid the “large amount of slopping” in the middle stage of blowing, if Cf <Ccrit = 11 at the time of the amount of acid sent of 2000 Nm ³ , it is necessary to change the blowing conditions at this point It can be determined that there is.

  Whether or not it was necessary to change the operating conditions during blowing using Bf = 7 and Ccrit = 11 determined as described above for 5 charges of dephosphorization and decarburization blowing of general dredge shown in Table 2 below I tried to determine whether.

As shown in the table, charge no. B1 to B3 are the operating conditions during the blowing because the cumulative number of times Cf exceeds Ccrit = 11 when a exceeds the Bf at the time of oxygen delivery amount of 2000 Nm ³ after the start of blowing from the end of the desiliconization period. Is determined not to need to be changed. These charges do not change the operating conditions during blowing even in the actual operation, but during the blowing, the charge remains “no slopping” or “sloping small” and the blowing can be completed. did it.

On the other hand, charge no. B4 and B5 are the operating conditions during the blowing because the cumulative number of times Cf is less than Ccrit = 11 when a exceeds the Bf at the time of the feed amount of 2000 Nm ³ after the start of blowing from the end of the desiliconization period. Is determined to need to be changed. However, in the actual operation, the operating conditions were not changed during the blowing, so the “sloping was large” and the operation had to be stopped halfway.

  Therefore, if the present invention is applied to the dephosphorization and decarburization blowing operation of general dredging, it is possible to easily and accurately determine whether or not the operating conditions need to be changed at an early stage during blowing, and the operation by slapping in the middle stage of blowing It was confirmed that the target molten steel could be produced stably without causing the stoppage.

[Example 3] Dephosphorization and decarburization blowing operation (treated steel, high carbon steel blowing)
Regarding the multiple charges of dephosphorization and decarburization blowing at which the treated soot is blown at P: 0.025% or less and C: 0.5% or more, the reaction status in the furnace at each charge is evaluated using the exhaust gas data. In order to avoid the “large slopping” and to secure the target dephosphorization rate, an attempt was made to determine whether or not the operating conditions had to be changed.

  The operating conditions of the dephosphorization and decarburization blowing of the treated slag in this example are as follows.

-Hot metal conditions Charging amount: 250-275ton
Hot metal components before blowing:
C = 4%
Si = 0.01-0.04%
P = 0.01-0.03%
Molten steel composition after blowing:
C = 0.5-0.9%
P = 0.004 to 0.025%
・ Top blowing condition ε _T = 1 to 3 kW / ton
・ Bottom blowing condition ε _B = 0.15 to 0.25 kW / ton

Here, both definitions of ε _T and ε _B are the same as those in the first and second embodiments.

  Further, as in Examples 1 and 2, the sampling interval of the exhaust gas flow rate was 1 s and Δt = 5 s.

  In the dephosphorization blowing of Example 1, the achievement of the target post-treatment phosphorus concentration is the highest priority, and in the general phosphorus dephosphorization decarburization blowing of the above Example 2, the suppression of slipping is the highest priority. On the other hand, in the dephosphorization and decarburization blowing of the treatment tank of the present embodiment, the achievement of the target dephosphorization rate and the suppression of the slopping are the highest priority issues.

  FIG. 11 shows an example of a change with time of a for each of the charge at which the dephosphorization rate after blowing achieved the target dephosphorization rate (0.5) and the charge that could not be achieved.

  As shown in FIG. 11, the time variation of a shows substantially the same behavior from the end of the desiliconization period to 400 seconds, which is about ½ of the entire blowing. Also in this example, as in Example 1 above, the blowing status is evaluated at about ¼ 200 s of the entire blowing, and from the end of the desiliconization period to 200 s after the start of blowing. A in the period (predetermined period after desiliconization) was used.

  As a result of calculating a for a plurality of charges, the value of a in the period from the end of the desiliconization period to the time of 200 s after the start of blowing (predetermined period after desiliconization) is as shown in FIG. In the charge in which the rate could not achieve the target dephosphorization rate, the rate changed within the range of “−7.5” to “7.5”. On the other hand, as shown in FIG. 11A, the value of “a” during the same period is approximately in the range of “−1.0” to “1.0” when the post-treatment phosphorus concentration reaches the target phosphorus concentration. Changed.

  Therefore, in this example, it was determined that it was effective to set an allowable range Bf between “1.0” and “7.5” that does not require the operation condition to be changed during the blowing.

  From the above, in order to determine Bf, a value in increments of “0.5” between “1.0” and “7.5” is taken as the candidate value Bi of Bf, and as schematically shown in FIG. For each Bi, the number of times exceeding the value of Bi was integrated to obtain the cumulative number Ci. And the correlation between this Ci and the dephosphorization rate which is one of blowing indexes was investigated.

FIG. 12 illustrates the result of investigating the correlation between Ci and the dephosphorization rate by linear regression when Bi = 2.0, 3.5, 6.0, and obtaining the correlation coefficient. is there. FIG. 12 shows the relationship between the correlation coefficient R ² obtained in this way and the candidate value Bi. As shown in the figure, when the candidate value Bi is “3.5”, the correlation coefficient R ² is maximized. Therefore, in this embodiment, “3.5” is adopted as Bf.

  Since “3.5” is adopted as Bf, the cumulative number Cf that satisfies the target dephosphorization rate of 0.5 or less is calculated using FIG. 12B where the candidate value Bi is “3.5”. Threshold Ccrit. The max was determined as “5”.

  That is, the cumulative number of times C exceeds Bf between the end of the silicon removal period and 200 s after the start of blowing, Cf> Ccrit. When max = 5, it can be seen that there is a high probability (possibility) that the dephosphorization rate cannot reach 0.5 if blowing is continued under that condition. In other words, in order to achieve the target dephosphorization concentration of 0.5 or more, Cf> Ccrit. It is possible to determine that it is necessary to change the blowing conditions when max = 5 (that is, when Cf = 6).

  On the other hand, if the FeO generation at the initial stage of blowing is excessive, there is a risk that “sloping is large” due to the rapid generation of CO gas in the middle stage of blowing. For this reason, it is necessary to consider not excessively generating FeO at the initial stage of blowing. When the swing width of a at the initial stage of blowing is small, there is a tendency to generate FeO, and the cumulative number of times Cf exceeding Bf decreases. As shown in FIG. 12, since “large slipping” occurred when Cf = 0, the threshold value Ccrit. min was determined to be “1”.

  That is, the cumulative number of times C exceeds Bf at the time of 200 s after the start of blowing from the end of the silicon removal period Cf <Ccrit. When min = 1 (that is, when Cf = 0), it is found that if blowing is continued under that condition, there is a high probability (possibility) of reaching “large slipping” in the middle of blowing. In other words, in order to avoid “sloping large” in the middle of blowing, Cf <Ccrit. When min = 1 (that is, Cf = 0), it is possible to determine that the blowing condition needs to be changed.

  For 5 charges of dephosphorization and decarburization blowing of the treated soot shown in Table 3 below, Bf = 3.5, Ccrit. max = 5 and Ccrit. Using min = 1, an attempt was made to determine whether the operating conditions had to be changed during blowing.

  As shown in the table, charge no. C1 to C3 indicate that the cumulative number of times Cf exceeds Bf at the time of 200 s from the end of the desiliconization period and 200 s after the start of blowing. min = 1 and Ccrit. Since it is between max = 5, it is determined that there is no need to change the operating conditions during the blowing. These charges do not change the operating conditions during blowing even in actual operation, but no slopping occurs during blowing, and the dephosphorization rate after blowing is the target of 0.5 The above has been achieved.

  On the other hand, charge no. C4 indicates that the cumulative number of times Cf exceeds Bf at the time of 200 s after the start of blowing from the end of the desiliconization period is Ccrit. Since it is less than min = 1, it is determined that it is necessary to change the operation condition during the blowing. However, in the actual operation, the operating conditions were not changed during the blowing operation, resulting in a “sloping large”, and although the dephosphorization rate of the blowing operation achieved the target dephosphorization rate, the subsequent operation Had to stop for a long time.

  In addition, charge No. C5 is the cumulative number of times Cf exceeds Cfrit at the time of 200 seconds after the start of blowing from the end of the desiliconization period. Since it exceeds max = 5, it determines with it being necessary to change an operating condition during the said blowing. However, in the actual operation, since the operation conditions were not changed during blowing, the target dephosphorization rate could not be achieved.

  Therefore, if the present invention is applied to the dephosphorization and decarburization blowing operation of the treated slag, it is possible to easily and accurately determine whether or not the operating conditions need to be changed at an early stage during blowing, and the operation by slapping in the middle stage of blowing It was confirmed that molten steel of the desired quality could be manufactured stably without incurring a stop.

Claims (3)

In the dephosphorization blown operation or dephosphorization decarburization blown operation using a converter, the progress of the reaction in the furnace is evaluated by the fluctuation of the exhaust gas flow rate at the initial stage of the blown operation after the desiliconization, and during the blown operation A method for determining whether or not it is necessary to change operating conditions,
The exhaust gas flow rate time variation a defined by the following formula (1) is calculated at regular intervals during the predetermined period after the silicon removal, and the number of times Cf that the instantaneous value of the exhaust gas flow time variation a deviates from the allowable range Bf. Count
The number of times Cf is compared with a threshold Ccrit to determine whether or not the operation conditions need to be changed during the blowing operation.
The predetermined period after desiliconization is a period from the end of the desiliconization period to the time of a predetermined amount of acid sent that is 1/4 or less of the total amount of acid sent.
The allowable range Bf and the threshold value Ccrit are calculated in advance in the predetermined period after desiliconization based on operation data of a plurality of blowing operations performed in the past of the same type as the above (1 From the correlation between the exhaust gas flow rate time change degree a defined in) and the blowing index in the blowing operation, it is determined from those that do not require changing the operating conditions during the blowing operation.
A method for determining whether or not to change operating conditions during converter blowing.
a = {Q (t + Δt) −Q (t)} / Δt (1)
Here, Q: exhaust gas flow rate, t: time, Δt: time interval.   In comparison with the threshold value Ccrit, when the number of times Cf satisfies the conditional expression that defines the magnitude relationship between the number of times Cf and the threshold value Ccrit, the operation condition is determined during the blowing operation. 2. While determining that there is no need to change, when the number of times Cf does not satisfy the conditional expression, it is determined that the operation condition needs to be changed during the blowing operation. To determine whether or not the operating conditions need to be changed during converter blowing.   The said blowing index is 1 type (s) or 2 or more types selected from the group which consists of the phosphorus density | concentration after blowing, the dephosphorization rate before and behind blowing, and the generation | occurrence | production state of the slopping in blowing. Or the determination method of the necessity of a change of the operating condition in the converter blowing of 2 or 2.

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