TWI804075B - Operation method of converter and blowing control system of converter - Google Patents

Abstract

The present invention provides a converter operation method for controlling the temperature of the molten metal at the point in time when the sub-lance is put in midway to a range in which the temperature and composition of the molten steel when blowing is stopped can hit the target value by means of correction in dynamic control. The converter operation method of the present invention uses static control and dynamic control to control the temperature and composition of the molten steel at the time of blowing stop blowing to the target value, and in the oxygen blowing of molten iron, the estimated value of the temperature of the molten metal is estimated successively, that is, blowing The estimated value of the temperature during refining and the estimated value of the carbon concentration in the molten metal, that is, the estimated value of carbon concentration during blowing (S-4), calculates the predetermined intermediate temperature at a specific period (S-5) before putting the sub-lance The difference between the target value and the predicted value of the temperature of the molten metal at the time when the subgun is put in, that is, the predicted value of the intermediate temperature (intermediate temperature difference) (S-6), when the absolute value of the calculated intermediate temperature difference is greater than the predetermined threshold When the value of the sub-gun is not used, the cooling material or heating material (S-8, S-10) is put into the converter before the sub-gun is put in, and the temperature of the molten metal during the sub-gun input period is controlled.

Description

Operation method of converter and blowing control system of converter

The present invention relates to a method for operating a converter for producing molten steel from molten iron by blowing oxidizing gas from a top blowing lance to molten iron in the converter for oxygen blowing, and a blowing control system for the converter.

In a converter for producing molten steel from molten iron, molten iron is decarburized and refined by blowing with oxygen from a top-blown lance (hereinafter also simply referred to as "blowing") to produce molten steel. In this converter operation, static control and dynamic control are performed as a blowing control method for making the temperature of molten steel or the concentration of molten steel components at the time of oxygen blowing stop (end) hit the target value. Among them, the static control is the following control: before the start of blowing, it is calculated according to the information of molten iron and iron filings used in the blowing to set the molten steel temperature and molten steel composition at the target value when the blowing is stopped. Calculate the required oxygen supply, and calculate the amount of auxiliary materials used to set the molten steel temperature and molten steel composition at the target value when the blowing is stopped.

The dynamic control is the following control: the measured value of the sub-lance (molten metal temperature, or molten metal temperature and melt Both the carbon concentration in the metal), adapt the amount of oxygen supplied or the auxiliary materials input, and adjust the molten steel temperature and molten steel composition to the target value when the blowing is stopped. The input of the sub-lance on the way was performed at the point in time when the oxygen amount obtained by subtracting a specific amount of oxygen from the supplied oxygen amount required by the static control was supplied to obtain the measured value of the sub-lance.

With static control, when the deviation between the measured value of the sub-lance and the target molten steel temperature and target carbon concentration when blowing is stopped becomes large, it is difficult to perform correction in dynamic control. As a result, the molten steel temperature or the carbon concentration and/or oxygen concentration in molten steel at the time of blowing stop largely deviated from the target values.

When the molten steel temperature is higher than the target temperature when the blowing is stopped, the blowing time is prolonged due to the cooling material being put into the furnace, the productivity is deteriorated, and the melting loss of the lining refractory of the converter becomes large, and the lining refractory Increased maintenance costs. On the other hand, when the temperature of molten steel at the time of blowing stop is lower than the target temperature, blowing is resumed, and the temperature rises due to combustion of iron (Fe) in molten steel. Since the blowing is restarted, the oxygen content in the molten steel at the time of the blowing stop becomes higher than the target value, the input amount of metal aluminum (Al) for deoxidizing the molten steel increases, and the manufacturing cost increases. In this case, due to restarting blowing, the carbon content in molten steel at the time of blowing stop usually falls below the target value.

Therefore, a technology is required to make the molten steel temperature and molten steel components (carbon concentration, oxygen concentration) at the time of oxygen blowing stop blowing reach target values.

In order to use static control and dynamic control to make the molten steel temperature and molten steel composition hit the target value when the blowing is stopped, it is necessary to adjust the temperature of the molten metal or the carbon concentration in the molten metal at the point when the sub-lance is put in through the correction in the dynamic control The measured value of the sub-lance is controlled to be within the range where the molten steel temperature and molten steel composition can easily hit the target value when the blowing is stopped.

Previously, as a method for determining the time point of sub-lance input in the middle, for example, in Patent Document 1, the time required for dynamic control is determined according to the blowing conditions, and the amount of oxygen blown in is calculated by using the determined dynamic control time, and blown into the static control The time point at which the oxygen amount obtained by subtracting the calculated oxygen amount (pre-supply amount) from the calculated oxygen amount (pre-supply amount) is determined as the time point at which the midway subgun is introduced.

Also, in Patent Document 2 and Patent Document 3, the emission spectrum, exhaust gas flow rate, and exhaust gas component concentration observed from the furnace mouth of the converter are measured, and the carbon concentration in the furnace is successively estimated, thereby reducing the time for the decarburization oxygen efficiency to decrease. The point is determined as the switching time point between the static control and the dynamic control, that is, the input time point of the sub-gun midway. [Prior art literature] [Patent Document]

Patent Document 1: Japanese Patent Laid-Open No. 2007-327113 Patent Document 2: Japanese Patent Laid-Open No. 2020-105611 Patent Document 3: International Publication No. 2019/220800

[Problem to be Solved by the Invention]

However, the method disclosed in Patent Document 1 uses static control to determine the measurement time point of the sub-gun in the middle, and the measurement time point of the sub-gun in the middle becomes inappropriate when the blowing conditions change due to disturbance. As a result, the following problems may occur: the time for dynamic control cannot be ensured; or it takes time from the insertion of the sub-lance midway until the blowing is stopped, and the accuracy of dynamic control decreases.

In addition, in Patent Document 2 and Patent Document 3, regardless of how the blow tempering situation changes, the timing of putting in the subgun in the middle is determined based on the calculated value successively calculated from the measured value. However, even if the sub-gun is put into the midway at the determined time point, the measured molten metal temperature or the carbon concentration in the molten metal may not be in the range that can be corrected by subsequent dynamic control.

That is, Patent Documents 1 to 3 only determine the time point when the sub-gun is put in, and do not disclose that the temperature of the molten metal or the carbon concentration in the molten metal at the time point when the sub-gun is put in is easily controlled by correction in the dynamic control. The technical idea of making the molten steel temperature and molten steel composition hit the range of the target value when the blowing is stopped.

The present invention has been made in view of the above circumstances, and its object is to provide a method for operating a converter that uses static control and dynamic control to control the molten steel temperature and molten steel composition to target values when blowing is stopped. , and through the correction in the dynamic control, the temperature of the molten metal at the point when the sub-lance is put in halfway can be controlled to the range that can make the molten steel temperature and molten steel composition hit the target value when the blowing is stopped. Also, a converter blowing control system for performing the converter operating method is provided. [Means to solve the problem]

The gist of the present invention to solve the above-mentioned problems is as follows.

[1] A method of operating a converter, in which, during blowing in which an oxidizing gas is blown to the molten iron in the converter to decarburize and refine the molten iron, a sublance is put into the furnace, and at least the melting of the molten metal in the furnace is carried out. The measured value of the sub-lance of the metal temperature is measured, and based on the measured value of the sub-lance obtained from the actual measurement, the amount of oxygen that should be supplied when the blowing is stopped and whether to put in cooling material or heating material and the input amount are determined, so as to stop the blowing. The temperature and component concentration of the molten steel at the time are controlled as the target value, and Determine the target value of the molten metal temperature when the sub-lance is put in, that is, the target value of the intermediate temperature, and determine the prediction of the intermediate temperature target value and the molten metal temperature for the time when the sub-lance is put in during blowing before the sub-lance is put in. The difference between the mid-point temperature prediction value of the value is the confirmation time point for confirmation of the mid-point temperature difference, Based on the operating conditions and measured values of the converter obtained at the start of blowing and during blowing, the estimated value of the temperature of the molten metal at the point in time when the blowing is in progress, that is, the estimated value of the temperature during blowing, and the estimation of the carbon concentration in the molten metal are successively estimated The value is the estimated value of carbon concentration in blowing, and After the blowing has been carried out to the confirmation time point, the intermediate temperature difference is calculated based on the estimated temperature during blowing and the estimated carbon concentration during blowing, When the absolute value of the calculated intermediate temperature difference is greater than a predetermined threshold value, the cooling material is injected into the converter or the temperature is raised during blowing after the confirmation time point and before the sub-lance is put in. material input.

[2] The method for operating a converter according to [1] above, wherein the confirmation time point is determined by an estimated value of carbon concentration during blowing.

[3] The method for operating a converter according to [2] above, wherein the confirmation time point is determined within a range in which the estimated carbon concentration during blowing is within a range of 0.6% by mass to 1.4% by mass.

[4] The method for operating a converter according to any one of [1] to [3] above, wherein the predetermined threshold value is selected from values of 10° C. or higher.

[5] The method for operating a converter according to any one of [1] to [4] above, wherein when the absolute value of the intermediate temperature difference is greater than a predetermined threshold value, at The amount of the cooling material or the amount of the heating material injected in the blowing after the confirmation time point and before the sub-lance is put in is based on the estimated value of the temperature in the blowing and the target value of the molten steel temperature when the blowing is stopped. and the amount of quicklime thrown into the converter during the blowing is determined by one or more of them.

[6] The method for operating a converter according to any one of [1] to [5] above, wherein the measured values of the converter obtained at the start of blowing and during blowing include Either or both of the measured values obtained by the gas flow meter and the exhaust gas analyzer.

[7] The method for operating a converter according to any one of [1] to [6] above, wherein the measured value of the converter obtained at the start of blowing and during blowing is the same as that of blowing. The measured values related to the optical properties of the converter mouth portion during smelting include the change rate of the luminous intensity of the spectrum derived from the reduction reaction of iron oxide in the slag.

[8] The method for operating a converter according to any one of the above [1] to the above [7], wherein the measured values of the converter obtained at the start of blowing and during blowing are included as The temperature of the molten iron measured by non-contact optical method when the molten iron used as the raw material for blowing flows into the converter from the molten iron holding container.

[9] A blowing control system for a converter, comprising: a sub-lance for controlling at least the melting of molten metal in the furnace during blowing in which an oxidizing gas is blown to the molten iron in the converter to decarburize and refine the molten iron The sub-gun measurement value of the metal temperature is measured; The first computer sequentially estimates the estimated value of the temperature of the molten metal at the point in time when the blowing is in progress, that is, the estimated value of the temperature during blowing, and the temperature in the molten metal, based on the operating conditions and measured values of the converter obtained at the start of blowing and during blowing. The estimated value of the carbon concentration is the estimated value of the carbon concentration during blowing, and based on the measured value of the sub-lance measured by the sub-lance, it is calculated that the temperature and component concentration of the molten steel when the blowing is stopped are set as target values. The amount of oxygen supplied and whether to put in cooling material or heating material and the amount of input; The computer for operation control, based on the amount of oxygen calculated by the first computer and the input amount of the cooling material or heating material, the temperature of molten steel and the carbon concentration in molten steel when blowing is stopped are set as target values to control the operating conditions; The second computer sets the target value of the molten metal temperature at the time when the sub-lance is put in, that is, the target value of the intermediate temperature, and sets the target value of the intermediate temperature and the molten metal at the time when the sub-lance is put in during blowing before the time when the sub-lance is put in. The difference between the predicted value of the temperature and the predicted value of the midway temperature, that is, the confirmation time point at which the midway temperature difference is confirmed, and Calculate the difference between the intermediate temperature target value and the intermediate temperature prediction value, that is, the intermediate temperature difference, and based on the calculated absolute value of the intermediate temperature difference, after the confirmation time point and before the sub-lance is put into the blowing , to determine whether to input the cooling material or the heating material into the converter; and The third computer calculates the input amount of the cooling material or the input amount of the heating material when the cooling material or the heating material is injected.

[10] The converter blowing control system described in [9] above, wherein the exhaust gas treatment equipment of the converter includes an exhaust gas flow meter and an exhaust gas analyzer, and the exhaust gas flow meter and the exhaust gas analyzer are used to The exhaust gas data measured by the gas analyzer is sent from the exhaust gas flowmeter and the exhaust gas analyzer to the first computer, and the first computer uses the sent exhaust gas data for blowing It is constituted by sequential estimation of the middle temperature estimated value and the carbon concentration estimated value during blowing.

[11] The blowing control system of the converter as described in [9] or [10], comprising: a spectroscopic camera, arranged around the converter, to photograph the combustion flame at the furnace mouth from the gap between the converter and the movable cover; and an image analysis device, which records the image data sent from the spectroscopic camera in an extractable manner, and calculates the luminous intensity of the luminescence spectrum of the image data at wavelengths in the range of 580 nm to 620 nm, and converts the The data of the luminous intensity is sent from the image analysis device to the first computer, and the first computer uses the sent data of the luminous intensity to estimate the temperature during blowing and the estimated carbon concentration during blowing. constituted in a sequential manner.

[12] The blowing control system of the converter according to any one of the above [9] to the above [11], comprising a temperature measuring device for optically measuring The temperature of the molten iron used as the raw material is charged into the converter as the temperature of the molten iron at the time of charging, and the data of the measured temperature value obtained by the temperature measuring device is sent from the temperature measuring device to the The first computer is configured to use the transmitted temperature measurement value data for sequential estimation of an estimated temperature during blowing and an estimated carbon concentration during blowing. [Effect of the invention]

According to the present invention, in the converter operation method that uses static control and dynamic control to control the molten steel temperature and molten steel composition to the target values when the blowing is stopped, through the correction in the dynamic control, the half-way sub-lance is put into the time point to be lowered. The temperature of the molten metal is controlled within the range that can make the molten steel temperature and molten steel composition hit the target value when blowing is stopped, so the molten steel temperature and molten steel composition can hit the target value with high precision when blowing is stopped.

Hereinafter, the operating method of the converter and the blowing control system of the converter according to the present invention will be described.

In the converter operation in which molten iron is decarburized and refined by oxygen blowing from a top blowing lance to produce molten steel, in order to determine the molten steel temperature and carbon concentration when the oxygen blowing is stopped (at the end) The component concentration is controlled to a target value, and blowing control combining static control and dynamic control is performed. Also in the operating method of the converter of the present invention, blowing is controlled by combining static control and dynamic control.

Static control uses a numerical model based on heat balance calculation and material balance calculation to determine the amount of oxygen supplied and the input amount of cooling materials or heating materials required to control the temperature of molten steel and the concentration of molten steel components to target values before blowing begins . Then, start blowing based on the determined oxygen supply amount and the input amount of cooling material or heating material, after blowing for a certain period of time (for example, blowing in 80% to 90% of the calculated oxygen supply amount in static control) time, etc.), put the sub-gun into the furnace. The temperature of the molten metal in the furnace, or both the temperature and the carbon concentration of the molten metal in the furnace are measured using the sublance. The sub-lance thrown into the converter in the middle of blowing is also called "mid-way sub-lance".

In the dynamic control, the measured value of the sub-lance (the molten metal temperature, or both the molten metal temperature and the carbon concentration in the molten metal) measured by the sub-lance, and a numerical model based on heat balance and material balance and a reaction model are used, Correct the oxygen supply amount or the input amount of cooling material or heating material determined in the static control, and finally determine the oxygen supply amount and the input amount of cooling material or heating material until the blowing is stopped.

Here, "molten metal" is molten iron or molten steel. In oxygen blowing or decarburization refining in a converter for producing molten steel from molten iron, the molten iron charged into the furnace is converted into molten steel by decarburization reaction. In the middle of oxygen blowing, it is difficult to distinguish molten iron and molten steel, so in this specification, molten iron and molten steel are collectively indicated as molten metal. In the case where molten iron and molten steel can be clearly distinguished, it is expressed as "molten iron" or "molten steel".

Calculation formulas for heat balance calculation under static control include, for example, a heat input determining term, a heat output determining term, a cooling term or a temperature rising term, an error term, and an operator-dependent temperature correction term. In addition, the formula for calculating the oxygen supply amount (oxygen supply amount) includes, for example, molten iron composition, auxiliary material input amount, target molten steel temperature and target molten steel composition when blowing is stopped.

However, the static control is calculated based on the information before blowing starts. Therefore, when the change of the furnace condition or the change of the height of the lance or the amount of oxygen supply leads to changes in the secondary combustion rate or the yield of auxiliary materials, the static control will error occurs. That is, there may be a case where the timing of putting the subgun on the way determined by the static control is not accurate. Therefore, in Patent Document 2 or Patent Document 3, based on converter exhaust information (exhaust gas flow rate, exhaust gas composition) or furnace mouth spectroscopic information, the carbon concentration of molten metal in blowing is estimated successively, and the decarburization oxygen efficiency At the point when it starts to lower, put in the sub-gun halfway. Here, "decarburization oxygen efficiency" is the ratio of oxygen that participates in the decarburization reaction among the oxygen supplied into the furnace, and "lance height" is the distance from the tip of the top blowing lance to the still bath surface of molten iron in the converter. Also, "secondary combustion" is a phenomenon in which CO gas generated in the furnace due to decarburization reaction is combusted into CO ₂ gas by oxygen supplied from the top blowing lance.

However, control using only the estimation of the change in carbon concentration during blowing is not sufficient to control the temperature of molten steel and the carbon concentration in molten steel within the target range when blowing is stopped.

The inventors of the present invention have made intensive studies and found that the temperature of the molten metal at the point when the sub-lance is put in midway varies as a reason why the control accuracy of the molten steel temperature does not improve when the blowing is stopped. In particular, it is found that the time point of putting in the sub-gun on the way determined by the time point at which the decarburization oxygen efficiency starts to decrease obtained by successive estimation of the carbon concentration in the molten metal and the time point of putting in the middle sub-gun determined in the static control When the deviation is large, the deviation of the molten metal temperature at the time when the subgun is thrown in the middle becomes large.

It is considered that the reason for the deviation at the time point when the subgun was put into operation is that the blown oxygen is not used for the reaction with the components or auxiliary materials in the molten metal estimated in the static control, but is used for example for secondary combustion or in the molten metal. Deviations in the proportion of iron burned. However, it is difficult to accurately reflect these deviations in static control.

Therefore, the present inventors think that not only the carbon concentration of the molten metal in blowing is estimated, but also the temperature of the molten metal is estimated successively, and the molten metal temperature at the time point when the sub-lance is thrown in the middle can be obtained by using the successively estimated values of the molten metal temperature. By dynamically controlling the range of correction, it is sufficient to implement the action (behavior, operation) to adjust the temperature of the molten metal before putting the sub-gun in the middle.

The method described in Patent Document 2 or Patent Document 3 can be applied to the sequential estimation of the carbon concentration of molten metal in the present invention. That is, based on the measurement results of the temperature and component concentration of the molten metal, information on the flow rate and component concentration of the exhaust gas, and information on the optical characteristics of the mouth portion of the converter based on at least any one of before and during blowing Estimate the amount of carbon in the molten metal (the spectroscopic results of the furnace mouth, the information on the optical properties of the furnace mouth), the information on the amount and speed of oxygen feeding, the information on the flow rate of the gas used for stirring, and the information on the input amount of raw materials (main raw materials and auxiliary materials). concentration. Here, as the information related to the optical characteristics of the furnace mouth portion of the converter, for example, the emission spectrum of the furnace mouth combustion flame sprayed from the furnace mouth of the converter or the emission spectrum of the tapping hole combustion flame can be measured and calculated. It is obtained by the temporal change of the emission intensity at the wavelength in the range of 580 nm to 620 nm of the measured emission spectrum.

The sequential estimation of the molten metal temperature in the present invention is performed as follows. First of all, in order to minimize the oxygen balance in the furnace, according to the oxygen supply amount or the input amount of oxygen such as iron oxide and the exhaust flow rate and exhaust gas composition (CO gas concentration, CO ₂ gas concentration, O ₂ gas concentration, etc. ) is corrected for the oxygen output obtained, thereby obtaining the amount of oxygen used for the combustion of carbon in the molten metal. Then, the carbon concentration in the molten metal is estimated from the amount of carbon in the burned molten metal. At this time, the calculated change in carbon concentration is converted into heat of reaction, thereby estimating the molten metal temperature.

Furthermore, in the estimated calculation of the molten metal temperature, not only the reaction heat of carbon and oxygen in the molten iron component is used as a calculation item, but also the reaction heat of silicon, manganese, phosphorus, and iron and oxygen in the molten iron component is used as a calculation item, In addition, the heat absorption of iron filings and auxiliary materials, the sensible heat of gas corresponding to the exhaust flow rate, and the heat dissipation corresponding to the temperature of the converter iron sheet are taken as calculation items. The heat of reaction is corrected by multiplying the coefficient determined from past operation results by regression so that the error between the measured value of the molten metal temperature obtained by the intermediate subgun and the calculated molten metal temperature is minimized.

The difference between the molten metal temperature at the time when the decarburization oxygen efficiency starts to decrease and the estimated molten metal temperature at the time when the sub-lance is put in during the process calculated by the conventional static control is calculated as a standard deviation of 1σ It is 19.6°C. Relative to the temperature error of the molten metal temperature at the time when the decarburization oxygen efficiency starts to decrease and the estimated molten metal temperature at the time when the sub-lance is put in through successive calculations of the molten metal temperature It is 14.4° C. with a standard deviation of 1 σ. That is, by calculating the temperature of the molten metal successively to determine the time point when the sub-gun is put in, thereby improving the temperature estimation accuracy at the time point when the sub-gun is put in.

For example, when the unit consumption of quicklime in the furnace is 5 kg to 15 kg/ton of molten iron, as the molten steel temperature and carbon concentration in molten steel when the blowing is stopped, set the target molten steel temperature ± 10°C and the target carbon concentration ± 0.015% by mass was set as the target range. In this case, confirm that if the carbon concentration in the molten metal is 0.1% to 0.3% by mass at the point when the sub-lance is put in halfway, the temperature of the molten metal at the point when the sub-lance is put in halfway is "target temperature when blowing is stopped - 35°C" To the range of 'the target temperature at the time of blowing stop -65 ℃', the simultaneous hit rate of the molten steel temperature and the carbon concentration in the molten steel at the time of stopping the blowing is high (88%).

In the present invention, the carbon concentration in the molten metal at the point when the sub-lance is thrown in the middle and the molten metal temperature at the point when the sub-lance is thrown in the middle are set within the above-mentioned ranges.

Next, an example of an embodiment of the present invention will be described in accordance with the steps of oxygen blowing. FIG. 1 shows an example of a flowchart of a blowing control system performed in accordance with the steps of oxygen blowing.

Firstly, the molten iron conditions (S-1) such as the temperature of the molten iron to be used or used in blowing, the charged amount of molten iron, and the composition of the molten iron are obtained.

Next, in this blowing, the following two points are determined (S-2). The time of confirmation may be any time as long as it is before the confirmation time point of (2) below, but from the viewpoint of time allowance, it is preferably before about 1/2 of the scheduled blowing time Determined, preferably before starting blowing.

(1) The setting of the midway temperature target value: The "intermediate temperature target value" is the target value of the molten metal temperature at the time of putting on the subgun halfway.

(2) Confirm the setting of the time point: 'Confirmation time point' is the target value of the molten metal temperature at the time when the sub-gun is put in during blowing, that is, the target value of the molten metal temperature at the time when the sub-gun is put in during the blowing process, that is, the "intermediate temperature target value" and the molten metal temperature at the time when the sub-gun is put in The time point (period or time point) at which the difference between the predicted value of the 'intermediate temperature prediction value', that is, the 'intermediate temperature difference' is confirmed.

The 'intermediate temperature target value' is preferably determined by considering the target molten steel temperature and the amount of slag in the furnace when the blowing is stopped. For example, it is preferably obtained by combining a linear expression of the target molten steel temperature at the time of blowing stop and a polynomial of the unit consumption of quicklime to be charged into the furnace during blowing as in the following expression (1). Furthermore, formula (1) is a combination of the polynomial of the unit consumption of quicklime that is scheduled to be input, and the polynomial of the unit consumption of quicklime that is scheduled to be input can be replaced by a polynomial of the amount of slag in the furnace based on the unit consumption of quicklime that is scheduled to be input .

Intermediate temperature target value (°C) = stop blowing target molten steel temperature (°C) - a × W - b × W ² -c... (1) Here, W is the unit consumption of quicklime in the blowing (kg/molten iron-ton), a (°C×molten iron-ton/kg), b (°C×(melt iron-ton) ² /kg ² ), and c (°C) are coefficients. The coefficient a, the coefficient b, and the coefficient c are set from past operation results using regression calculation so that the hit rate at the time of blowing off is the highest.

In addition, the confirmation time point is determined based on the successive estimated values of the carbon concentration in the molten metal, such as the time point at which the estimated value of the carbon concentration in the molten metal calculated successively during blowing becomes 1.0% by mass. In particular, it is preferable to determine the time point at which the successive estimated value of the carbon concentration in the molten metal is within the range of 0.6% by mass to 1.4% by mass as the confirmation time point.

When determining the time point when the successively estimated value of the carbon concentration in the molten metal exceeds 1.4% by mass as the confirmation time point, the confirmation time point is too early, and there is a risk of being unable to cope with changes in the blowing conditions thereafter. On the other hand, when the time point when the successively estimated value of the carbon concentration in the molten metal is less than 0.6% by mass is determined as the confirmation time point, the confirmation time point is too late, and there is a problem during the period from the confirmation time point to the midway subgun injection. There is a possibility that the sub-gun may be used for measurement before all the added auxiliary materials (cooling material and heating material) are reacted, so there is a possibility that the accuracy of the dynamic control performed thereafter may be reduced.

During the blowing after the start of blowing, the exhaust gas information such as the flow rate and composition of the converter exhaust gas is obtained step by step. At the same time, the oxygen supply information (S-3) of the oxygen supply amount and oxygen supply speed from the top blowing lance is also obtained successively.

In addition, in the blowing after the start of blowing, a numerical model based on heat balance calculation and material balance calculation is used, based on the data obtained at the start of blowing and during blowing obtained in step (S-1) and step (S-3). The obtained operating conditions and measured values of the converter are successively estimated values of the temperature of the molten metal at the point in time when the blowing is in progress, i.e. the 'in-blowing temperature estimated value' and the successive estimated values of the carbon concentration in the molten metal, i.e. 'the carbon in blowing Estimated Concentration' (S-4).

The decarburization reaction proceeds with the progress of the blowing, and reaches the "confirmation time point" (S-5) at which the estimated value of the carbon concentration in the blowing calculated successively falls within the range of 0.6% by mass to 1.4% by mass. After the blowing progresses to the confirmed time point, the predicted value of the molten metal temperature at the sub-lance input period, that is, the 'intermediate temperature predicted value' is calculated. The "intermediate temperature prediction value" is determined at the point of confirmation by successively estimated values of carbon concentration in the molten metal, and the value of this carbon concentration, that is, the "estimated value of carbon concentration during blowing" is set to C _X (mass %) In the case of , it is estimated using the following formula (2).

Predicted value of intermediate temperature (°C)=T(C _X )+d×(C _X -C _SL )...(2) Here, T(C _X ) is the 'estimated value of carbon concentration in blowing' and C _X (mass %) at the time point of 'Blowing Temperature Estimated Value' (°C), C _X is the 'Blowing Carbon Concentration Estimated Value' (mass %) at the confirmation time point, C _SL is the scheduled time point when the sub-lance is put into the middle carbon concentration (mass %). d is the molten metal temperature rise rate (° C./mass %) when 1.0 mass % of carbon in the molten metal is burned, and it is preferable to use a value obtained by regression from the past actual results of converter blowing.

That is, the 'predicted value of midway temperature' is obtained from the 'estimated value of temperature during blowing' and 'estimated value of carbon concentration during blowing' as shown in the above-mentioned formula (2).

Then, the "intermediate temperature difference" is calculated using the obtained "intermediate temperature target value" and the obtained "intermediate temperature predicted value" (S-6).

The 'intermediate temperature target value' is expressed by (1) formula, and the 'intermediate temperature predicted value' is expressed by (2) formula. Therefore, according to (1) and (2) formulas, the 'intermediate temperature predicted value' when the subgun is put in midway The difference from the "intermediate temperature target value", that is, the "intermediate temperature difference" is represented by the following formula (3).

Mid-way temperature difference (°C) = mid-way temperature prediction value (°C) - mid-way temperature target value (°C) = T (C _X ) + d × (C _X -C _SL ) - [stop blowing target molten steel temperature (°C) - a×W－b×W ² －c]...(3) The case where the 'intermediate temperature difference' calculated by the formula (3) exceeds 0 (zero) corresponds to the case where the 'intermediate temperature predicted value' is higher than the 'intermediate temperature target value'', on the other hand, the case where the 'intermediate temperature difference' is less than 0 (zero) corresponds to the case where the 'intermediate temperature predicted value' is lower than the 'intermediate temperature target value'.

Therefore, regardless of whether the 'intermediate temperature difference' is a positive number or a negative number, when the absolute value of the 'intermediate temperature difference' is large, it is necessary to perform an action (behavior, operation) of correcting the molten metal temperature. That is, when the absolute value of the 'intermediate temperature difference' is greater than a predetermined threshold value, it is necessary to take an action to make the 'intermediate temperature predicted value' approach the 'intermediate temperature target value' after the operation.

Therefore, it is determined whether or not the 'intermediate temperature difference' is larger than a predetermined threshold value (positive number) (S-7). When the 'intermediate temperature difference' is a positive number and exceeds a threshold value (positive number), a coolant is injected in order to lower the molten metal temperature (S-8).

When the 'intermediate temperature difference' is equal to or less than a predetermined threshold value (positive number), it is determined whether the 'intermediate temperature difference' is smaller than the threshold value (negative number) (S-9). When the 'intermediate temperature difference' is a negative number and is smaller than a threshold value (negative number), a heating material is injected in order to increase the molten metal temperature (S-10).

When the absolute value of the "intermediate temperature difference" is equal to or less than a predetermined threshold value, the operation for adjusting the molten metal temperature is not performed.

For example, if the predetermined threshold value is set to 15°C, when the "intermediate temperature difference" exceeds +15°C, the "intermediate temperature predicted value" after the action is reduced to approach the "intermediate temperature target value". In this way, cooling materials such as scale or iron ore are put into the furnace to cool the molten metal. The input amount of cooling material is determined by multiplying the cooling coefficient by the 'intermediate temperature difference'. On the other hand, when the 'intermediate temperature difference' is less than -15°C, for example, the carbon material is put into the furnace so that the 'intermediate temperature predicted value' after the operation rises and approaches the 'intermediate temperature target value' (by The temperature is raised by the combustion of contained carbon), or Fe-Si alloy (the temperature is raised by the combustion of contained silicon (Si)) to raise the temperature of molten metal. The input amount of heating material is determined by multiplying the "intermediate temperature difference" by the heating coefficient.

The threshold value predetermined as the absolute value of the "intermediate temperature difference" may be appropriately determined according to the circumstances of individual steelmaking plants, and is preferably a value selected from values of 10° C. or higher. For example, it is determined to be 15°C.

If the absolute value of the "intermediate temperature difference" is less than 10°C, even if the cooling material or the heating material is not put into the converter during the blowing after the confirmed time point and before the sub-lance is put in, the dynamic control corrections. Therefore, the predetermined threshold value may be set to a value of 10° C. or higher. In addition, when the absolute value of the "intermediate temperature difference" is larger, in the blowing after the confirmed time point and before the sub-lance is put in, by increasing the amount of cooling material or heating material in the converter, , and the smaller the correction amount using dynamic control, the easier it is to make the molten steel temperature and molten steel composition hit the target value when the blowing is stopped, so there is no need to determine the upper limit of the absolute value.

Then, based on the successive estimated values of the carbon concentration in the molten metal, that is, the "estimated value of carbon concentration during blowing", the time point at which the decarburization oxygen efficiency starts to decrease (as described below in the "estimated value of carbon concentration during blowing" It becomes approximately 0.45% by mass), and the subgun is put into the middle at this time point.

After the midway sub-lance is put in, dynamic control is implemented based on the measured value of the sub-lance measured by the midway sub-lance, and the operation shown in the dynamic control is performed to end the oxygen blowing.

By performing the above operations, the temperature control of the molten metal at the point when the sub-lance is put in becomes easier than before, and the molten steel temperature when the blowing is stopped can be accurately controlled to the target value by the subsequent dynamic control.

In the embodiment of the present invention, it is important to perform sequential estimation of the 'in-blowing temperature estimated value' and the 'in-blowing carbon concentration estimated value' more accurately in order to further express the effect. Therefore, as the measured value of the converter obtained at the start of blowing and during blowing, it is preferable to use the exhaust gas obtained by using the above-mentioned exhaust gas flowmeter installed in the flue of the exhaust gas treatment equipment of the converter. Either or both of the measured value of the flow rate and the measured value of the exhaust gas component (CO gas concentration, CO ₂ gas concentration, O ₂ gas concentration, etc.) obtained by the exhaust gas analyzer. Furthermore, it is preferable to employ other measured values useful for sequential estimation of the 'in-blowing temperature estimated value' and the 'during blowing carbon concentration estimated value' in combination with these.

For example, as the measured value of the converter to be used, it is preferable to use a measured value related to the optical characteristics of the furnace mouth portion of the converter during blowing, and it is a change in the emission intensity of the spectrum derived from the reduction reaction of iron oxide in the slag. Rate. By adopting this value, the successive estimation accuracy of the carbon concentration in the molten metal during blowing improves. Specifically, as the optical characteristics of the mouth of the converter, the reduction reaction of iron oxide in the slag represented by the reaction formula of the following (4) formula, in the wavelength band (spectrum) of the light emitted by the decarburization reaction For example, the maximum value of the emission intensity in the wavelength band of 550 nm to 650 nm is detected, and the measured value is used.

FeO+C→Fe+CO...(4) It is known that if the carbon concentration in the molten metal reaches near the critical carbon concentration by sending oxygen for decarburization, the efficiency of the decarburization reaction (decarburization oxygen efficiency) shown in the formula (4) will decrease, resulting in Luminous intensity also decreases. Here, the 'critical carbon concentration' is the melting under the boundary where the decarburization reaction rate of oxygen decarburization moves from the state limited by the supply rate of oxygen to the state limited by the movement (diffusion) of carbon in the molten metal carbon concentration in the metal. In other words, the 'critical carbon concentration' is the carbon concentration in the molten metal at the point when the decarburization oxygen efficiency starts to decrease. Furthermore, the critical carbon concentration varies depending on the agitation force of the top blowing gas and the bottom blowing gas on the molten metal and the flow rate of the oxidizing gas, but it is approximately 0.45% by mass.

Therefore, in the embodiment of the present invention, it is preferable to calculate the rate of change of the emission intensity of the maximum value of the emission intensity in the above wavelength band and reflect it in the sequential estimation of the carbon concentration in the molten metal during blowing. For example, the time point when the rate of change of the luminous intensity changes from a positive value to a negative value can be detected as the time point when the carbon concentration in the molten metal reaches a critical carbon concentration.

Also, for example, it is preferable that the measured value used include the temperature of the molten iron measured using a non-contact optical method when the molten iron used as the raw material for blowing flows into the converter from the molten iron holding container. By adopting this value, the successive estimation accuracy of the 'temperature estimation value during blowing' is improved.

Specifically, it is preferable to use a value determined based on the temperature of the molten iron measured when the molten iron holding container flows into the converter as the initial value of the "in-blowing temperature estimated value". Usually, as this initial value, the temperature measured by immersing a thermocouple in the molten iron filled in the molten iron holding container before loading into the converter is used. However, after measuring the temperature of the molten iron in the molten iron holding container, the temperature of the molten iron in the molten iron holding container drops before it is loaded into the converter. Not reflected in the initial value. Therefore, it is preferable to measure the temperature of the molten iron during charging of the molten iron into the converter, and to set a value determined based on the temperature as an initial value of the 'in-blowing temperature estimated value'. The initial value of 'Temperature Estimated Value During Blowing' can be directly used for the temperature of the molten iron measured from the molten iron holding vessel when it flows into the converter, and it can also be used considering the previously charged tapping to the current loading. The value obtained by correcting the temperature of the molten iron measured when the molten iron holding vessel flows into the converter from the time until the molten iron is melted, that is, the empty furnace time or the amount of iron filings charged.

The measurement of the temperature of the molten iron when the molten iron flows from the molten iron holding vessel into the converter was performed using a non-contact optical method. As this optical method, specifically, it is preferable to use a so-called dichroic thermometer that measures the luminescence spectrum emitted from the molten iron, and uses two different wavelengths selected from the measured luminescence spectrum. The temperature of the molten iron is calculated from the radiant energy ratio. The reason is that by using a dichroic thermometer as a temperature measuring device to optically measure the temperature of molten iron, even when the emissivity of the temperature measurement object changes, as long as the relationship between the two spectral emissivities with different wavelengths remains proportional If the relationship changes, the ratio of the two spectral emissivities depends only on temperature, and the temperature can be accurately measured regardless of changes in the emissivity.

Here, when the two different wavelengths used by the dichroic thermometer are set to λ1 and λ2 (λ2>λ1), it is desirable that both λ1 and λ2 are in the range of 400 nm to 1000 nm. When λ1 and λ2 are less than 400 nm, since the wavelength is short, it is difficult to detect radiant energy with a general spectroscopic camera. On the other hand, when λ1 and λ2 exceed 1000 nm, since the wavelength is long, the influence of emissivity ratio fluctuation is large. Furthermore, it is preferable that the absolute value of the difference between λ1 and λ2 is not less than 50 nm and not more than 600 nm. When the absolute value of the difference between λ1 and λ2 is less than 50 nm, since the wavelengths of λ1 and λ2 are close to each other, it is difficult to split light with a normal spectroscopic camera, which is not preferable. On the other hand, when the absolute value of the difference between λ1 and λ2 exceeds 600 nm, one of the wavelengths (λ2) must be selected from the range of long wavelengths. Since the wavelength is long, the influence of emissivity ratio changes is large, so it is insufficient good.

When the molten iron used as raw material for blowing flows from the molten iron holding container into the converter, the temperature of the molten iron measured using a non-contact optical method is used as the initial value of the 'in-blowing temperature estimated value' When the decarburization oxygen efficiency starts to decrease, the molten metal temperature when the sub-lance is put into the midway and the temperature of the "predicted value of blowing temperature" at the time point when the sub-lance is put in through the successive calculation of the molten metal temperature The error is reduced to 12.9°C in terms of standard deviation 1σ. That is, by using the value determined based on the temperature of the molten iron measured using a non-contact optical method when it flows into the converter as the initial value of the 'in-blowing temperature estimated value', the temperature at the point when the sub-gun is put in halfway is estimated Accuracy is further improved.

As the measured value of the converter used, the measured value related to the optical characteristics of the mouth of the converter during blowing (the rate of change of the luminescence intensity of the spectrum derived from the reduction reaction of iron oxide in the slag) In the case of both the molten iron temperature measured when the molten iron used as the raw material flows into the converter from the molten iron holding container, either measurement can be handled by a spectroscopic camera. That is, even one spectroscopic camera can measure both. Here, a spectroscopic camera is generally a general term for a camera that can also capture spectroscopic data in addition to a plane image for temperature measurement such as a so-called thermal view. Note that the spectroscopic data is data obtained by collecting a plurality of wavelengths included in emitted light for each wavelength.

Hereinafter, the configuration of a converter plant including a blowing control system suitable for implementing the converter operating method of the present invention will be described with reference to the drawings. Figure 2 shows a schematic diagram of a suitable converter plant for the practice of the invention.

The suitable converter equipment 1 that implements the present invention comprises: converter 2; An image analyzing device 8 records the photographed image captured by the spectroscopic camera 7 in an extractable manner, and analyzes the photographed image; the first computer 9 inputs the data analyzed by the image analyzing device 8; and The computer 12 for operation control inputs the data analyzed by the first computer 9 .

Furthermore, it includes: the second computer 10, which inputs the data analyzed by the first computer 9; and the third computer 11, which inputs the data analyzed by the second computer 10. The data analyzed by the second computer 10 and the data analyzed by the third computer 11 are input to the computer 12 for operation control. The first computer 9 , the second computer 10 and the third computer 11 may also include one computer. The computer 12 for operation control transmits a control signal based on the data input from the 1st computer 9 and the 3rd computer 11.

Furthermore, it includes a spray gun height control device 13, a sub-lance lifting control device 14, an oxidizing gas flow control device 15, and a bottom blowing gas flow control device 16, which can be separately actuated by control signals sent from the operation control computer 12. , and auxiliary material input control device 17. The spray gun height control device 13 is a device for adjusting the spray gun height of the top blowing spray gun 3 , and the sub-lance lifting control device 14 is a device for controlling the descent and rise of the sub-lance 5 . The oxidizing gas flow control device 15 is a device for adjusting and measuring the flow rate of the oxidizing gas injected from the top blowing lance 3 . The bottom blowing gas flow control device 16 is a device for adjusting the flow rate of the stirring gas blown in from the bottom blowing port 4, and the auxiliary material input control device 17 is to control the kind and input amount of the auxiliary material contained in the furnace upper hopper 24 installation.

Feedback control is performed by inputting respective actual performance values from these control devices to the computer 12 for operation control. Here, auxiliary material is a general term for solvents such as quicklime, cooling materials such as iron ore, and heating materials such as carbon materials. Compared with auxiliary materials, the main raw materials are molten iron and iron filings.

Furthermore, an exhaust gas flowmeter 22 for measuring the flow rate of the exhaust gas discharged from the rotary furnace 2 and for analyzing the composition of the exhaust gas is provided in the flue 29 for exhaust gas discharge that is arranged on the top of the furnace mouth 20. (CO gas, CO ₂ gas, O ₂ gas, etc.) gas analyzer 23. Each measured value obtained by the exhaust flow meter 22 and the gas analyzer 23 is input into the first computer 9 .

The structure of the converter 2 used in the present invention is that the oxidizing gas jet 19 can be sprayed from the top blowing lance 3 to the molten iron 6 in the furnace, and the stirring gas can be blown from the bottom tuyere 4 at the bottom of the furnace at the same time. As the oxidizing gas blown from the top blowing lance 3, pure oxygen (industrial pure oxygen) or a mixed gas of oxygen and an inert gas can be used. Usually pure oxygen is used as the oxidizing gas.

The converter processing computer (not shown) inputs the composition (C, Si, Mn, P, S, etc.), temperature, quality, and the blown iron 6 used in the blowing (feeding) to the first computer 9. The quality (loading amount) of iron filings in smelting and other information. Further, the measured value of the sub-lance obtained by the sub-lance 5 , that is, the measured value of the molten metal temperature, or the measured values of both the molten metal temperature and the carbon concentration in the molten metal is input to the first computer 9 . Furthermore, from the converter processing computer, the target value of molten steel temperature and the target value of molten steel component concentration such as carbon concentration are input to the first computer 9 when oxygen blowing is stopped (at the end). In addition, the target value of the molten steel temperature and the target value of the concentration of molten steel components such as the carbon concentration at the time of the blowing stop of the oxygen blowing can also be directly set in the first computer 9 .

The first computer 9 is based on the target value of the molten steel temperature and the target value of the molten steel component concentration when the blowing is stopped based on the input of the blowing, and the input composition, temperature, quality and The mass of iron filings is statically controlled using a numerical model based on heat balance calculation and material balance calculation. Then, the first computer 9 calculates the oxygen supply amount, solvent input amount, and cooling material or heating material input amount required to control the molten steel temperature and molten steel component concentration at the time of blowing stop to target values as data for static control. That is, the first computer 9 implements static control before blowing starts.

The static control data obtained by the first computer 9 are input into the computer 12 for operation control. The computer 12 for operation control is based on the static control data input from the first computer 9, and sends control to the spray gun height control device 13, the oxidizing gas flow control device 15, the bottom blowing gas flow control device 16, and the auxiliary material input control device 17 respectively. Signal, so that the temperature of molten steel and the concentration of molten steel components when the blowing is stopped become the target values. Thus, blowing by static control starts.

The first computer 9 uses a numerical model based on heat balance calculation and material balance calculation in the blowing after the start of blowing, and successively estimates based on the operating conditions and measured values of the converter obtained at the start of blowing and during blowing. The "in-blowing temperature estimated value" which is the sequentially estimated value of the molten metal temperature at each time point in blowing progress, and the "during blowing carbon concentration estimated value" which is the successively estimated value of the carbon concentration in the molten metal.

As a method of successively estimating the "estimated value of carbon concentration during blowing", for example, the supply amount of the oxidizing gas input from the oxidizing gas flow control device 15, the carbon content of the molten iron 6 before oxygen blowing input from the converter processing computer, etc. are used. Concentration, the measured value of the exhaust gas flow rate input from the exhaust gas flow meter 22, and the measured value of the exhaust gas composition input from the gas analyzer 23 are used to calculate the material balance of carbon and oxygen in the decarburization reaction, and estimate the gas content in the furnace. Carbon concentration of molten metal.

The second computer 10 sets the above-mentioned 'interim temperature target value' and 'confirmation time point'. The "intermediate temperature target value" which is the target value of the molten metal temperature during the injection period of the subgun is calculated using the above-mentioned (1) formula. The set period may be any time as long as it is before the 'confirmation time point', but it is preferably determined before about 1/2 of the scheduled blowing time, more preferably before starting blowing.

Here, the "confirmation time point" is as described above, which is the predicted value of the "intermediate temperature target value" and the molten metal temperature at the time of sub-lance input during the period before the sub-lance input during blowing, that is, " The difference between the intermediate temperature prediction value' is the time point at which the 'intermediate temperature difference' is confirmed. Furthermore, the confirmation time point is preferably determined as the time point at which the "in-blowing carbon concentration estimated value" of the successive estimated values obtained by the first computer 9 falls within the range of 0.6% by mass to 1.4% by mass. .

During blowing, the first computer 9 will send the signal of the "estimated carbon concentration in blowing" to the "confirmation time point" calculated by the first computer 9 successively. Enter the second computer 10 . When the "confirmation time point" is input from the first computer 9, the second computer 10 calculates the "predicted midway temperature value" using the above-mentioned (2) formula. Then, using the calculated 'intermediate temperature prediction value' and the calculated 'intermediate temperature target value', the 'intermediate temperature difference' is calculated by the above-mentioned (3) formula.

The second computer 10 determines whether to inject a cooling material or a heating material into the converter in the blowing before the sub-lance is loaded, based on the obtained absolute value of the "intermediate temperature difference". Specifically, for example, the threshold value of the absolute value of the "intermediate temperature difference" is set at 15°C, and when the "intermediate temperature difference" exceeds +15°C, it is determined that scale or iron ore, etc. are thrown into the furnace. As for the cooling material, on the other hand, when the 'intermediate temperature difference' is less than -15°C, it is determined that a heating material such as a carbon material or an Fe-Si alloy is thrown into the furnace. In this case, if the absolute value of the "intermediate temperature difference" is 15 degrees C or less, input of a cooling material and a heating material will not be implemented. When the 'intermediate temperature difference' is a positive number exceeding +15°C, the cooling material is put in, and when the 'intermediate temperature difference' is a negative number exceeding -15°C, the heating material is put in. The absolute value of the midway temperature difference' becomes smaller. That is, the difference between the intermediate temperature target value and the intermediate temperature predicted value at the point of insertion of the subgun becomes smaller by the input of the cooling material or the heating material. The second computer 10 transmits the presence or absence of input of the cooling material or the heating material to the third computer 11 and the operation control computer 12 .

When a signal that the cooling material or the heating material is injected is input from the second computer 10, the third computer 11 calculates the input amount of the cooling material or the input amount of the heating material. The input amount of the cooling material and the heating material is calculated based on the absolute value of the 'intermediate temperature difference'. For example, if the cooling material is iron ore, when the 'intermediate temperature difference' exceeds +15°C and is below +20°C, put in a cooling material with a unit consumption of 2.7 kg/molten iron-ton, and in the 'intermediate When the temperature difference' exceeds +20°C and is below +25°C, put in cooling materials with a unit consumption of 3.6 kg/molten iron-ton, and when the 'intermediate temperature difference' is a positive number, the 'intermediate temperature The larger the difference' is, the more the input amount of the cooling material is increased. On the other hand, when the "intermediate temperature difference" is a negative number, the larger the absolute value of the "intermediate temperature difference", the more the input amount of the heating material is increased.

The calculated input amounts of the cooling material and the heating material are sent from the third computer 11 to the computer 12 for operation control. The computer 12 for operation control, which receives the input amount signal of the cooling material and the heating material from the third computer 11, sends a control signal to the auxiliary material input control device 17 to inject a specific amount of cooling material or heating material into the furnace. The auxiliary material input control device 17 that receives the control signal injects a specific amount of cooling material or heating material into the furnace.

Thereafter, when the "estimated value of carbon concentration during blowing" successively calculated by the first computer 9 becomes the carbon concentration (approximately 0.45% by mass) at which the decarburization oxygen efficiency begins to decrease, the first computer 9 sends the signal to the operation Computer 12 for control. The operation control computer 12 that has received the signal sends a control signal for subgun drop-in to the subgun elevating control device 14 . The sub-gun lifting control device 14 that receives the control signal drops into the sub-gun 5 in the furnace.

The sublance 5 measures the molten metal temperature, or both the molten metal temperature and the carbon concentration in the molten metal. Here, the molten metal temperature is measured by a thermocouple provided in the sub-gun probe at the tip of the sub-gun 5 . In addition, the carbon concentration in the molten metal is obtained from the cooling curve when the molten metal collected by the molten metal sampler in the subgun probe is solidified in the molten metal sampler. The measured value of the sub-lance obtained by the sub-lance 5 , that is, the measured value of the molten metal temperature, or the measured values of both the molten metal temperature and the carbon concentration in the molten metal is sent to the first computer 9 .

The first computer 9 calculates the amount of oxygen that should be supplied and whether to inject a cooling material or a heating material in order to set the temperature and component concentration of the molten steel when the blowing is stopped as target values based on the measured value of the sub-lance 5 actually measured by the sub-lance 5 . and input volume. That is, the first computer 9 implements dynamic control after putting in the sub-gun.

The dynamic control signal obtained by the first computer 9 is sent to the computer 12 for operation control. The operation control computer 12 having received the dynamic control signal obtained by the first computer 9 sends a control signal to the oxidizing gas flow control device 15 to supply a specific amount of oxidizing gas into the furnace. At the same time, a control signal is sent to the auxiliary material input control device 17 to inject a specific amount of cooling material or heating material into the furnace. The oxidizing gas flow control device 15 having received the control signal supplies a specific amount of oxygen into the furnace. In addition, the auxiliary material input control device 17 which receives the control signal from the computer 12 for operation control injects a specific amount of cooling material or heating material into the furnace.

After the supply of oxygen and the input of cooling material or heating material through the dynamic control of the first computer 9 are completed, the oxygen blowing is ended.

With the blowing control system of the above structure, it is easier to control the temperature of the molten metal at the point when the sub-lance is put in than before, and through the subsequent dynamic control, the temperature of the molten steel when the blowing is stopped can be accurately controlled. control to the target value.

In the present invention, in order to more accurately perform sequential estimation of the "estimated value of temperature during blowing" and "estimated value of carbon concentration during blowing", as described above, as the The measured value of the converter is preferably a measured value related to the optical characteristics of the converter mouth portion during blowing, and/or measured using a non-contact optical method when the molten iron flows from the molten iron holding container into the converter. The measured value of the temperature of the molten iron obtained.

In order to measure the measured values related to the optical characteristics of the mouth of the converter and the measured values of the temperature of the molten iron measured using a non-contact optical method, the converter equipment 1 used in the present invention includes a spectroscopic camera7. The symbol 25 in Fig. 2 is the input chute of the auxiliary material, the symbol 26 is the oxidizing gas supply pipe towards the top-blowing spray gun, the symbol 27 is the cooling water supply pipe towards the top-blowing spray gun, and the symbol 28 is the cooling water discharge from the top-blowing spray gun Tube.

A spectroscopic camera 7 is installed around the converter 2 at a position where the emission spectrum of the combustion flame 18 at the furnace mouth of the converter can be measured. With the installed spectroscopic camera 7, the combustion flame 18 at the furnace mouth that can be observed from the gap between the furnace mouth 20 and the movable cover 21 of the rotary furnace is photographed. The captured images (image data) captured by the spectroscopic camera 7 are sequentially sent to the image analysis device 8 . The transmitted captured image (image data) is recorded in the image analysis device 8, and line analysis is performed on any scanning line of the image data to analyze the emission wavelength and the emission intensity at each wavelength.

The analyzed image data of the combustion flame 18 at the furnace mouth is sent to the first computer 9 at any time. The first computer 9 uses the analysis image of the emission spectrum of the combustion flame 18 at the furnace mouth input from the image analysis device 8 when successively estimating the "estimated value of carbon concentration in blowing" by calculating the mass balance of oxygen and carbon. data, successively deduce the 'concentration estimated value of carbon in blowing'. Thereby, the estimation accuracy of the "in-blowing carbon concentration estimation value" improves.

Here, the "burning flame at the furnace mouth" refers to the flame in the furnace blown from the furnace mouth 20 of the rotary furnace 2 to the upper flue 29 . The emission spectrum of the combustion flame 18 at the furnace mouth includes CO gas generated by the decarburization reaction in the converter, and _CO2 generated by natural ignition due to the mixing of a part of the CO gas with the air sucked from the furnace mouth. Information related to gas, or information related to FeO* (intermediate product) from iron atoms evaporated from the fire point in the furnace.

The inventors of the present invention have confirmed that by measuring the emission intensity at each wavelength in real time in the wavelength range of 580 nm to 620 nm in the emission spectrum, it is possible to easily estimate the state of the converter in real time. Furthermore, the present inventors confirmed that when FeO* is produced, an absorption peak can be seen in this wavelength range, and on the other hand, when FeO* disappears, an emission peak can be seen in the same wavelength range, wherein the luminescence intensity is the same as that of FeO*. The disappearance speed is linked.

Monitor the electromagnetic waves of specific wavelengths that are emitted or absorbed when the electronic state of FeO*, which is mainly generated by the fire point of the molten iron bath in the furnace, changes. Since FeO* is integrated with the flame rising from the furnace, for example, the amount of FeO* produced and the amount of FeO* reacted decrease near the end of the decarburization reaction. Luminescence intensity decreases at wavelengths ~620 nm. That is, when the decarburization reaction rate becomes the rate-limiting mass transfer of carbon in the molten metal, the production of FeO becomes dominant over the reduction of FeO, and the emission intensity at a wavelength of 580 nm to 620 nm decreases rapidly.

Next, a method of measuring the temperature of the molten iron 6 using the spectroscopic camera 7 when the molten iron 6 used in blowing flows into the converter 2 from the molten iron holding container 30 will be described.

Fig. 3 is a schematic diagram showing the measurement of the temperature of molten iron flowing from the molten iron holding container into the converter. When the molten iron 6 used as the raw material for blowing flows into the converter 2 from the molten iron holding container 30, when the temperature of the molten iron is measured, the spectroscopic camera 7 is installed, for example, in front of the furnace on the loading side of the converter to measure the temperature of the molten iron. The position where the injection flow when the molten iron 6 flows into the converter 2 from the molten iron holding container 30 is observed. If the spectroscopic camera 7 is installed at an angle of looking up at the injection flow, it is less likely to be affected by the dust generated when the molten iron is charged, which is preferable. The spectroscopic camera 7 is used to collect the two-color temperature information at a preset sampling rate (for example, at intervals of 1 second) from the beginning to the end of molten iron loading.

The two-color temperature information collected by the spectroscopic camera 7 is sent to the image analysis device 8, and the molten iron temperature is calculated by the image analysis device 8. The calculated molten iron temperature is input to the first computer 9, and the first computer 9 uses the value determined based on the input molten iron temperature as the initial value of the "in-blowing temperature estimated value" to perform the "blowing temperature estimated value". 'The successive calculations.

By using the value determined based on the molten iron temperature measured by the spectroscopic camera 7 as the initial value of the 'in-blowing temperature estimated value', the accuracy of temperature estimation at the point in time when the subgun is put in is further improved.

As a method of measuring the two-color temperature information by the spectroscopic camera 7, a large amount of wavelength data can be collected in advance by the spectroscopic camera 7, and the data of any two wavelengths can be extracted from the obtained data by using the image analysis device 8, if it is spectroscopic A camera including a band-pass filter in the camera can also extract any two wavelengths through the band-pass filter. In addition, the imaging of the spectroscopic camera 7 is often performed by a charge-coupled-device (CCD) element, and a plurality of CCD elements may be mounted, and each CCD element measures another wavelength range.

Spectroscopy can be included for the measurement of the optical properties of the mouth of the converter during blowing (the rate of change in luminous intensity of the spectrum derived from the reduction reaction of iron oxide in the slag) and the measurement of the molten iron temperature during charging of the converter. The camera 7 can also be shared. In the case of sharing, the furnace mouth combustion flame 18 which can be seen from the gap between the furnace mouth 20 of the rotary furnace 2 and the movable cover 21, and the injection flow when the molten iron 6 flows into the converter 2 from the molten iron holding container 30 are both. The location where the observer takes the observation. Alternatively, a moving mechanism may be provided so that it can be installed at a position where the injection flow of the molten iron 6 from the molten iron holding container 30 into the converter 2 can be observed during charging of the molten iron, and blowing can be started after the molten iron is charged. Move forward to the position where the furnace mouth combustion flame 18 visible in the gap between the furnace mouth 20 of the rotary furnace 2 and the movable cover 21 can be observed.

As explained above, according to the present invention, in the converter operation method using static control and dynamic control to control the molten steel temperature and molten steel composition to the target values when the blowing is stopped, through the correction in the dynamic control, the halfway The temperature of the molten metal at the point when the sub-lance is put in is controlled within the range that can make the molten steel temperature and molten steel composition hit the target value when the blowing is stopped, so the molten steel temperature and molten steel composition can be kept at a high level when the blowing is stopped. Accuracy hits the target value. [Example]

After performing desulfurization and dephosphorization treatment on the molten iron in advance, use a 350-ton capacity top-bottom blowing converter (oxygen top blowing, argon bottom blowing) as shown in Figure 2. Oxygen blowing of 300 to 350 tons of molten iron is carried out under dynamic control, and the molten iron is decarburized and refined to produce molten steel. The target molten steel temperature at the time of stopping the blowing varies with each blowing, and is in the range of 1660°C to 1700°C. The hitting range of the target molten steel temperature when blowing is stopped in each blowing is the target molten steel temperature ±10°C. Table 1 shows the chemical composition and temperature of molten iron used in blowing.

[Table 1] Composition of molten iron (mass%) Melting iron temperature (℃) C Si mn P S Fe 2.5～2.9 0.01～0.08 0.04～0.15 0.016～0.042 0.007～0.016 Bal. 1350～1400

According to the relationship between the exhaust gas flowmeter and exhaust analyzer installed in the flue of the exhaust gas treatment equipment of the converter, and the amount of oxygen supplied from the top blowing lance and the amount of solid oxygen injected (iron ore, etc.), the furnace Determine the amount of combustion of the components in the furnace in such a way that the oxygen balance error in the furnace becomes the smallest. The obtained reaction amount of the components in the furnace is converted into the heat of reaction, and the "estimated value of temperature during blowing" is successively calculated. In addition, the successive estimation of the 'in-blowing carbon concentration estimated value' is performed based on the material balance calculation of oxygen and carbon.

When the molten iron is charged into the converter, the molten iron visible between the mouth of the converter and the molten iron holding container is photographed with a spectroscopic camera. The molten iron temperature when loaded into the converter was calculated from the luminescence intensities at wavelengths of 550 nm and 850 nm in the obtained luminescence spectrum of the molten iron. In addition, during blowing, the luminescence spectrum of the combustion flame at the furnace mouth was photographed by a spectroscopic camera, and the luminescence intensity at each wavelength was measured in real time for wavelengths in the range of 580 nm to 620 nm in the luminescence spectrum. Set the wavelength used to 610 nm. As the spectroscopic camera, one spectroscopic camera is used, and it is installed at a position where the combustion flame at the furnace mouth and the injection flow of the molten iron from the molten iron holding container into the converter can be observed by using a moving mechanism.

In the example of the present invention, the successive calculations of the "estimated temperature during blowing" were performed using the molten iron temperature measured at the time point when the molten iron was charged into the converter as the initial value of the "estimated temperature during blowing". In addition, when calculating and estimating the "estimated value of carbon concentration in blowing" using the material balance of oxygen and carbon, the "estimated value of carbon concentration in blowing" is successively estimated using the analytical image data of the emission spectrum of the combustion flame at the furnace mouth. .

Also, in the example of the present invention, the point at which the "estimated value of carbon concentration during blowing" becomes 1.2% by mass is determined as the "confirmation time point", and the target molten steel temperature when blowing is stopped for each blowing is determined using the above-mentioned The formula (1) described above is used to obtain the 'target value of midway temperature'. The 'intermediate temperature target value' is within the range from 'target molten steel temperature when blowing stops -35°C' to 'target molten steel temperature when blowing stops -65°C'.

Then, in the example of the present invention, the "intermediate temperature difference" was obtained using the formula (3) when the "estimated value of carbon concentration during blowing" reached 1.2% by mass. When the obtained 'intermediate temperature difference' exceeds +15°C, iron ore is put into the furnace as a cooling material until it is put into the intermediate sub-gun. On the other hand, when the 'intermediate temperature difference' is less than -15°C, a carbon material (with a carbon content of 75% by mass or more) is charged into the furnace as a heating material until the intermediate sub-lance is injected.

The input amount of the iron ore as the cooling material and the carbon material as the heating material is the value obtained by multiplying the cooling coefficient and the heating coefficient by the "intermediate temperature difference". The cooling coefficient and heating coefficient are respectively obtained by regression based on the previous blowing calculation results. The cooling coefficient is -0.18 [(iron ore・kg)/(molten iron・ton×℃)], and the heating coefficient is + 0.25 [(carbon material・kg)/(molten iron・ton×℃)].

Then, based on the successive estimated values of the carbon concentration in the molten metal, that is, the "estimated value of the carbon concentration during blowing", the time point at which the decarburization oxygen efficiency starts to decrease (the carbon concentration in the molten metal ≒ 0.45% by mass) is obtained, and at this time Point into the sub-gun halfway.

After the sub-lance is put in, dynamic control is performed based on the measured values of molten metal temperature and carbon concentration in the molten metal obtained by using the sub-lance, and the operation shown in the dynamic control is performed to end the oxygen blowing.

On the other hand, in the comparative example, the temperature of the molten iron measured at the time point when the molten iron was loaded into the converter was not used as the initial value of the "estimation value of the temperature during blowing", but the thermocouple was dipped before the molten iron was loaded into the converter. The temperature of molten iron measured in the molten iron filled in the molten iron holding container was used as the initial value of the "estimated value of temperature during blowing" to carry out successive calculations of "estimated value of temperature during blowing". In addition, the "estimated value of carbon concentration during blowing" was calculated and estimated using the mass balance of oxygen and carbon without using the analysis image data of the emission spectrum of the combustion flame at the furnace mouth.

Then, the sublance was injected at the time point when the "in-blowing carbon concentration estimated value" became 0.45% by mass. Dynamic control is performed based on the actual measurement values of the molten metal temperature and the carbon concentration in the molten metal obtained by the sub-lance on the way, and the operation shown in the dynamic control is performed to end the oxygen blowing.

Table 2 shows the test conditions and test results of the examples of the present invention and the comparative examples.

[Table 2] static control Temperature control of molten metal at [mass%C]=1.2 Halfway hit rate ^*1 (%) End hit rate ^*2 (%) Example of the invention have have 94 87 comparative example have none 40 60 *1: The measured value of the molten metal temperature obtained by using the intermediate sub-lance is ±15°C from the 'intermediate temperature target value' when the intermediate sub-lance is put into operation, and the measured value of the carbon concentration satisfies the ratio of 0.1% by mass to 0.3% by mass*2: The temperature of the molten steel when the blowing is stopped is the target temperature ± 10°C and the carbon concentration in the molten steel when the blowing is stopped meets the target carbon concentration ± 0.015% by mass

It can be confirmed that the hit rate when blowing is stopped (end point) in the example of the present invention is as high as 87%, and the hit rate when blowing is stopped (end point) is greatly improved compared with the comparative example.

4 is a graph showing the relationship between the molten metal temperature and the carbon concentration in the molten metal at the point in time when the subgun is introduced in the middle of the inventive example and the comparative example. According to Fig. 4, in the example of the present invention, it can be confirmed that the deviation of the molten metal temperature at the point when the sub-lance is put in halfway is reduced relative to the target molten steel temperature when the blowing is stopped, and the temperature of the molten metal at the point when the sub-lance is put in halfway is controlled. .

Fig. 5 is a graph showing the error between the target molten steel temperature and the actual molten steel temperature when blowing was stopped in Examples of the present invention and Comparative Examples. As shown in FIG. 5 , it was confirmed that the present invention can accurately control the molten steel temperature at the time of blowing stoppage to the target molten steel temperature.

1: Converter equipment 2: Converter 3: Top blowing spray gun 4: Bottom air outlet 5: Secondary gun 6: molten iron 7:Spectral camera 8: Image analysis device 9: First computer 10: Second computer 11: The third computer 12: Computer for operation control 13: Spray gun height control device 14: Secondary gun lifting control device 15: Oxidizing gas flow control device 16: Bottom blowing gas flow control device 17: Accessory material input control device 18: Burning flame at the furnace mouth 19: Oxidizing gas jet 20: Furnace mouth 21: Movable cover 22: Exhaust flow meter 23: Gas analyzer 24: Furnace Hopper 25: Input chute of auxiliary materials 26: Oxidizing gas supply pipe facing the top blowing lance 27: Cooling water supply pipe facing the top blowing spray gun 28: Cooling water discharge pipe from top blowing spray gun 29: flue 30: Molten iron holding container

Fig. 1 is a diagram showing an example of a flow chart of a blowing control system performed in accordance with an oxygen blowing step in an embodiment of the present invention. Figure 2 is a schematic diagram of a converter plant including a blowing control system suitable for practicing the invention. Fig. 3 is a schematic diagram of measuring the temperature of molten iron flowing from a molten iron holding vessel into a converter. Fig. 4 is a graph showing the relationship between the molten metal temperature and the carbon concentration in the molten metal at the point in time when the subgun is inserted in the middle of the inventive example and the comparative example. Fig. 5 is a graph showing the error between the target molten steel temperature and the actual molten steel temperature when blowing was stopped in Examples of the present invention and Comparative Examples.

Claims (12)

A method for operating a converter in which, during blowing in which an oxidizing gas is blown to molten iron in the converter to decarburize and refine the molten iron, a sublance is put into the furnace to control the temperature of the molten metal including at least the molten metal in the furnace. Based on the measured value of the sub-lance, determine the amount of oxygen that should be supplied when the blowing is stopped and whether to put in cooling material or heating material and the amount of input, so as to reduce the amount of oxygen that should be supplied when the blowing is stopped. The temperature and component concentration of molten steel are controlled to target values, and the target value of the molten metal temperature at the time when the sub-lance is put in, that is, the target value of the half-way temperature is determined, and the target value of the half-way temperature is determined during blowing before the time when the sub-lance is put into operation , The difference between the predicted value of the temperature of the molten metal at the time when the sub-lance is put into operation and the predicted value of the middle temperature, that is, the confirmation time point of the half-way temperature difference, is based on the operating conditions and measurements of the converter obtained when blowing is started and during blowing value, successively estimate the estimated value of the molten metal temperature at the time point when the blowing is carried out, that is, the estimated value of the temperature in blowing, and the estimated value of the carbon concentration in the molten metal, that is, the estimated value of the carbon concentration in blowing, and the blowing is carried out until the above-mentioned After confirming the time point, calculate the intermediate temperature difference based on the estimated temperature during blowing and the estimated carbon concentration during blowing, and when the absolute value of the calculated intermediate temperature difference is greater than a predetermined threshold value In the case of this case, the cooling material or the heating material is injected into the converter during the blowing after the confirmation time point and before the sub-lance is injected. The method for operating a converter according to Claim 1, wherein the confirmation time point is determined by the estimated value of the carbon concentration in blowing. The method for operating a converter according to claim 2, wherein the confirmation time point is determined within a range in which an estimated value of carbon concentration during blowing is 0.6% by mass to 1.4% by mass. The method for operating a converter according to any one of claim 1 to claim 3, wherein the predetermined threshold value is selected from values above 10°C. The method for operating a converter according to any one of claim 1 to claim 3, wherein, when the absolute value of the intermediate temperature difference is greater than a predetermined threshold value, after the confirmation time point and The amount of the cooling material or the amount of the heating material input in the blowing before the sub-lance is put in is based on the estimated temperature during the blowing, the target value of the molten steel temperature when the blowing is stopped, and the temperature during the blowing. Determined by one or more of the amount of quicklime put into the converter. The method for operating a converter according to any one of claim 1 to claim 3, wherein the measured values of the converter obtained at the start of blowing and during blowing include exhaust gas flowmeters and exhaust gas analysis. Either or both of the measured values obtained by the meter. The method for operating a converter according to any one of claim 1 to claim 3, wherein the measured value of the converter obtained at the start of blowing and during blowing is the same as that of the furnace mouth of the converter during blowing The measured values related to the optical properties of the slag include the change rate of the emission intensity of the spectrum derived from the reduction reaction of iron oxide in the slag. The method for operating a converter according to any one of claim 1 to claim 3, wherein the measured values of the converter obtained at the start of blowing and during blowing are included in the raw materials for the blowing. The molten iron used is the temperature of the molten iron measured by a non-contact optical method when the molten iron holding vessel flows into the converter. A blowing control system of a converter, comprising: a sub-lance, in blowing blowing oxidizing gas to the molten iron in the converter to decarburize and refine the molten iron, controlling the temperature of the molten metal at least including the molten metal in the furnace Actual measurement of the measured value of the sub-gun; the first computer, based on the operating conditions and measured values of the converter obtained at the start of blowing and during blowing, successively estimates the estimated value of the temperature of the molten metal at the point in time when blowing is in progress, that is, the temperature during blowing The estimated value and the estimated value of the carbon concentration in the molten metal, that is, the estimated value of the carbon concentration in blowing, and based on the measured value of the sub-lance measured by the sub-lance, calculate the temperature and temperature of the molten steel when the blowing is stopped. The amount of oxygen that should be supplied when the component concentration is set to the target value, and whether to put in the cooling material or the heating material and the input amount; the computer for operation control is based on the amount of oxygen calculated by the first computer and the cooling material or The input amount of the heating material controls the operating conditions so that the temperature of the molten steel and the carbon concentration in the molten steel become the target values when the blowing is stopped; the second computer sets the target value of the molten metal temperature when the sub-lance is input, that is, the mid-way temperature The target value, and the difference between the target value of the intermediate temperature and the predicted value of the intermediate temperature which is the predicted value of the molten metal temperature during the injection period of the auxiliary gun, that is, the intermediate temperature difference is set to confirm in the blowing before the injection period of the sub-lance. Confirm the time point, and calculate the difference between the intermediate temperature target value and the intermediate temperature prediction value, that is, the intermediate temperature difference. Based on the calculated absolute value of the intermediate temperature difference, after the confirmation time point and the sub-gun is put into In the previous blowing, it is determined whether to input the cooling material or the heating material into the converter; and the third computer, when the cooling material is input or the heating material is input, Calculate the input amount of the cooling material or the input amount of the heating material. The blowing control system of the converter as described in claim 9, wherein the exhaust gas treatment equipment of the converter includes an exhaust gas flow meter and an exhaust gas analysis meter, and the gas measured by the exhaust gas flow meter and the exhaust gas analyzer The exhaust gas data is sent from the exhaust gas flowmeter and the exhaust gas analyzer to the first computer, and the first computer uses the sent exhaust gas data for temperature estimation during blowing and Consists of sequential estimation of carbon concentration estimated value during blowing. The blowing control system of the converter as described in claim 9 or claim 10, comprising: a spectroscopic camera, arranged around the converter, and photographing the combustion flame at the furnace mouth from the gap between the converter and the movable cover; and an image analysis device, with The image data sent from the spectroscopic camera can be recorded in an extractable manner, and the luminous intensity of the luminous spectrum of the image data at a wavelength in the range of 580nm to 620nm is calculated, and the luminous intensity data is obtained from the The image analysis device sends to the first computer, and the first computer is configured to use the transmitted data of luminous intensity for sequential estimation of an estimated temperature during blowing and an estimated carbon concentration during blowing. The blowing control system of the converter according to claim 9 or claim 10, comprising a temperature measuring device for optically detecting that molten iron used as a raw material for blowing in the converter is charged into the The temperature of the molten iron during the converter is used as the temperature of the molten iron at the time of loading, and the data of the measured temperature value obtained by the temperature measuring device is sent from the temperature measuring device to the first computer, and the first computer It is configured to use the data of the transmitted temperature measurement value for sequential estimation of the temperature estimated value during blowing and the carbon concentration estimated value during blowing.

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