JPH11246907A - Method for controlling blowing in converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means with which a molten iron temp. and carbon concn. during blowing are accurately and surely controlled without executing the measurement with a sub-lance on a top-bottom combining blown converter. SOLUTION: A thermo-meter 13 is set in a molten iron 2 in a converter 1, the molten iron temp. is continuously measured and one or two more among on oxygen feeding speed, an interval between a lance and the molten iron surface and the adding quantity of an auxiliary raw material for cooling, are adjusted based on the temp. information. Further, in addition to the above, a carbon concn. measuring means is set in the molten iron 2 to measure the carbon concn. and the controls of the molten iron temp. and the carbon concn. during blowing are executed based on these information of the temp. and the carbon concn. Furthermore, a means for preventing the invasion of outer air by tightly closing the furnace opening part of the converter 1 at the time of blowing, a means for measuring CO, CO2 and inert gas concns. in an exhaust gas and a means for supplying a prescribed quantity of the inert gas into the converter and/or into an exhaust gas duct at the upstream side from the exhaust gas composition measuring point, are set and decarburized quantity is estimated based on the component concn. in the exhaust gas and the flow rate of the inert gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for accurately controlling the temperature and carbon concentration of molten iron during blowing to improve the efficiency of furnace reaction and reduce the melting of refractory in a converter in a top-bottom blown converter. The present invention relates to a method for controlling the blowing of a converter which is controlled reliably.

[0002]

2. Description of the Related Art In a steelmaking converter, it is necessary to control the molten steel temperature and carbon concentration at the end of blowing to predetermined values. In particular, in recent years, there has been a strong demand for improvement in steelmaking efficiency, and it has become necessary to control the end point as accurately as possible in order to avoid reblowing and the like.

Further, in order to increase the efficiency of a furnace reaction such as dephosphorization, it is necessary to appropriately control the transition of the molten iron temperature during refining. Furthermore, in order to reduce the melting damage of the converter refractories, it is necessary to appropriately control the temperature at the end of blowing.

[0004] Therefore, dynamic control using a computer has been generally performed for controlling the blowing end point of a converter. This is because when estimating the transition of molten iron temperature and carbon concentration during blowing by material balance and heat balance calculations, etc., the estimation accuracy is improved by learning calculation based on information of preceding heat, and furthermore, sublance ( Measure the molten iron temperature and carbon concentration by measuring lance) and correct the trajectory,
It is intended to perform the blowing end point control reliably and accurately.

In order to further improve the accuracy of the dynamic control, there is also a so-called decarburization speed meter which measures information on exhaust gas, for example, the concentration of CO and CO _{2 in} exhaust gas, the flow rate of exhaust gas, and estimates the amount of decarburization from these. It is heavily used.

[0006]

The estimation of the molten iron temperature based on the heat balance calculation or the like has low accuracy. Further, the conventional decarburization speed meter based on exhaust gas information has a problem in measuring the exhaust gas flow rate, and its reliability is low. Therefore, in the conventional blowing control, it was indispensable to measure the molten iron temperature and the carbon concentration using a sublance and correct the trajectory.

However, the probe of the sublance (consumable thermocouple or consumable carbon terminator) is a consumable item, so that the cost is high and the reliability of the measurement is low at the beginning of blowing when the cold material such as scrap is not melted. For this reason, it is customary to measure at a specific time in the latter half of blowing (usually once), which is insufficient from the viewpoint of obtaining information on the entire blowing period.

On the other hand, in recent years, in order to increase the productivity of the converter, the yield of iron, and the like, there have been proposed a number of pressurized converter steelmaking methods in which the internal pressure of the converter is raised above the atmospheric pressure and blowing is performed (for example, see, for example). JP-B-43-9982, JP-A-2-20561, JP-A-2-298209, JP-A-4-160109, and the like.

In such a pressurized converter steelmaking method, measurement using a sublance is not preferable because its equipment and work are complicated. That is, a seal structure for the sliding portion of the sub-lance and a pressurizing chamber for probe replacement are required, and the furnace equipment becomes complicated. In addition, it is necessary to adjust the pressure of the pressurizing chamber to be equal to the pressure in the furnace, which imposes a heavy work load.

As described above, a new blowing control method that does not depend on the measurement by a sublance is used in both the converter operation under the existing atmospheric pressure and the converter operation under pressure, which may be put to practical use in the future. It is desired to provide.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides temperature control and end point control during blowing of a converter without performing measurement using a sublance in a converter operation under atmospheric pressure or pressure. It is an object of the present invention to provide means capable of accurately and reliably performing the above.

[0012]

Means for Solving the Problems The inventors of the present invention have made it possible to relatively easily and continuously measure a temperature by arranging a thermometer in an iron bath section of a converter with the recent advances in temperature measurement technology. It was found to be very useful for controlling the blowing of a converter.

Further, the present inventors have found that the furnace port can be easily sealed not only in a pressurized converter but also in a converter under atmospheric pressure. Inspired by the fact that low-concentration inert gas components can be analyzed with high accuracy, the results of various studies indicate that the amount of decarburization can be accurately estimated by measuring the mass balance of inert gas without measuring the exhaust gas flow rate. did.

The gist of the present invention based on these findings is that a thermometer is arranged in an iron bath in an upper and lower blown converter to continuously measure the molten iron temperature, and based on the temperature information, an acid feed rate and a lance pressure are measured. −
A blowing control method for a converter, comprising controlling one or more of a molten metal surface space and an added amount of a cooling auxiliary material to control a molten iron temperature during blowing.

Further, a thermometer and a carbon concentration measuring means are arranged in an iron bath in the top and bottom blown converter to measure the temperature and the carbon concentration of the molten iron, and based on the information on the temperature and the carbon concentration, the acid is fed. Blowing control of a converter characterized by controlling one or more of a speed, a lance-gap and a cooling auxiliary material addition amount to control a molten iron temperature and a carbon concentration during blowing. Is the way.

Further, a thermometer is arranged in an iron bath in the top and bottom blown converter to continuously measure the molten iron temperature, and the furnace opening of the converter is sealed during blowing to prevent outside air from entering. Means for measuring the concentration of CO, CO ₂ and inert gas in the exhaust gas, and means for supplying a predetermined flow rate of the inert gas into the converter furnace or / and the exhaust gas duct upstream of the exhaust gas composition measurement point. The decarburization amount is estimated on the basis of the concentration of components in the exhaust gas and the flow rate of the inert gas. By adjusting one or more of the additional amounts of auxiliary materials for
This is a method for controlling the blowing of a converter, wherein the temperature of the molten iron and the carbon concentration during the blowing are controlled.

[0017]

FIG. 1 is an explanatory diagram showing an example of an embodiment of the present invention. An iron bath 2 is formed in a converter 1 provided with an upper blowing lance 3 and a bottom blowing tuyere 4, and an auxiliary material is added from a hopper 7 for the auxiliary material to a cutting device 8 and a charging chute 9. .

A temperature measuring tuyere 10 is installed at the bottom of the converter 1, and an image fiber 12 is inserted into a nozzle for introducing a purge gas supplied from a purge gas supply line 11. Usually, Ar is used as the purge gas, but N ₂ or CO may be used. In addition, O ₂ , air, and CO ₂ can be supplied as needed to open the nozzle.

The information obtained by the image fiber 12 is subjected to image processing and signal processing by a signal processing and temperature measuring device 13 and then converted from luminance to temperature and output as temperature information. The measurement of the molten iron temperature does not need to be limited to the above-described optical method, but may be, for example, a durable protective tube type thermocouple.

The operating conditions are calculated based on the temperature information.
The instruction is an upper blowing gas flow control device 6, a lance position control device (not shown), and a cooling auxiliary material (one or two of iron ore, shredded scrap, limestone, and dolomite) provided in the upper blowing gas line 5. The molten iron temperature during blowing is controlled by adjusting one or more of the acid supply speed, the lance-to-gap surface distance, and the added amount of the cooling auxiliary material by being transmitted to the cutting device 8).

FIG. 2 is an explanatory diagram showing an example of the embodiment of the present invention described in claim 2. In the example of FIG.
The tuyere 10 for temperature measurement and the tuyere 14 for analysis are installed at the bottom of the furnace, and the molten iron temperature is measured as well as the molten iron carbon concentration as in FIG.

The analysis tuyere 14 has an analysis fiber 16 inserted into a nozzle for introducing a purge gas supplied from a purge gas supply line 15.
The carbon concentration is measured according to 7. Ar is used as a purge gas to measure light elements such as carbon,
₂ , CO may be used. In addition, O ₂ , air, and CO ₂ can be supplied as needed to open the nozzle.

As an analysis method, see, for example, JP-A-60-4
There is an analysis method utilizing emission by a laser as disclosed in Japanese Patent No. 2644.

As described above, by simultaneously obtaining the information on the molten iron temperature and the carbon concentration, one or more of the acid supply rate, the lance-to-gap spacing, and the added amount of the cooling auxiliary material are adjusted in the same manner as described above. Thereby, the molten iron temperature and the carbon concentration during blowing can be controlled to change in a predetermined pattern, and the control of the molten steel temperature and the carbon concentration at the end point of the blowing becomes easier and more reliable.

FIG. 3 is an explanatory diagram showing an example of the embodiment of the present invention described in claim 3. In the example of this figure, in addition to continuously measuring the molten iron temperature by the temperature measuring tuyere 10 provided at the furnace bottom of the converter 1 as in FIG. 1, the decarburization amount is estimated by the following method.

In the example shown in FIG. 3, the converter 1 is connected to a hood 19 by a furnace port sealing device 18 at the time of blowing, and the furnace port is sealed to prevent the intrusion of outside air. In the exhaust gas duct,
Means for analyzing the composition of the exhaust gas (in this example, a sample gas is collected from the sampling hole 20 and analyzed by the gas analyzer 21), and the concentrations of CO, CO ₂ and N ₂ in the exhaust gas are measured. Further, a gas inlet 22 is provided upstream of the exhaust gas duct, and a predetermined flow rate of N ₂ gas is blown into the duct via a flow meter 23.

The type of the furnace port sealing device 18 does not need to be particularly limited, and an appropriate method may be selected in consideration of heat resistance, workability and, if necessary, pressure resistance. Further, in order to more completely shut off the outside air, it is desirable to provide a lance hole sealing device 24 also in the insertion hole of the upper blowing lance 3 and to make the auxiliary material supply system a closed system.

Since the invasion of outside air can be completely prevented by the above means, the decarburization amount during oxygen blowing can be estimated by the following equation (1). ΔC = (12 / 22.4) · Q _n · ((CO + CO ₂ ) / N ₂ ) (1) where ΔC: decarburization amount (kg / min) Q _n : N ₂ gas flow rate ( Nm ³ / min) CO, CO ₂ , N ₂ : CO, CO ₂ , N ₂ concentration in exhaust gas
(vol.%).

The above equation is a basic equation, which is corrected by comparing the estimated value of the decarburization amount in the preceding heat with the actually measured value, or corrected by the space volume up to the exhaust gas composition measurement point. Can be increased in estimation accuracy.

The N ₂ gas is not necessarily blown into the duct, N ₂ used for other purposes, for example as a carrier gas of N ₂ and auxiliary raw material powder for bottom blowing, the sub-hole or the like of the oxygen lance It may be N ₂ blown from the air. Alternatively, these may be used in combination with N ₂ blowing into the duct.

In the example of FIG. 3, N _{2 is used} as the inert gas.
In this case, Ar may be used.
₂ and Ar may be used in combination.

Estimation of the amount of decarburization based on conventional exhaust gas information is as follows:
The reliability of the measured value of the exhaust gas flow rate was low, and the estimation accuracy was poor. On the other hand, according to the method of the present invention, the decarburization amount can be estimated without measuring or estimating the exhaust gas flow rate, and the estimation accuracy can be improved.

It was confirmed that the method of the present invention can accurately estimate the decarburization amount and the transition of the molten iron [C], as will be shown in Examples described later. Thereby, accurate blowing control can be performed without actually measuring the molten iron carbon concentration as in the example of FIG.

In the present invention, the molten iron temperature and the carbon concentration may be measured as in the example of FIG. 2, and the decarburization amount may be estimated by the method as shown in FIG. As described above, by having the means for obtaining the information on the decarburization amount and the carbon concentration redundantly, it is possible to cope with troubles such as measurement, and it is possible to reliably and accurately determine the transition of the carbon concentration.

According to the blowing control method of the present invention, it is not necessary to perform measurement using a sub-lance, so that the cost of consumables such as probes can be reduced, and the equipment for measuring the sub-lance in pressurized converter blowing is required. Work load can be eliminated.

Further, since the molten iron temperature or the information of the molten iron temperature and the carbon concentration can be continuously obtained from the initial stage to the early stage of the blowing, information such as improvement of dephosphorization reaction efficiency and reduction of refractory erosion can be obtained. Also useful above.

For example, in the early stage of blowing, the molten iron temperature is low and the dephosphorization ability is very large. However, since the initial temperature could not be measured and the temperature was not controlled, dephosphorization progressed in a short time after the start of blowing. It was a difficult high temperature range. As shown in Examples described later, it was confirmed that the dephosphorization proceeded extremely efficiently by setting the temperature in the period from 3 minutes to 6 minutes after the start of blowing to 1350 to 1500 ° C. by the method of the present invention. .

In addition, since the accuracy of the estimation of the molten iron temperature before the conventional blowing is not sufficiently high, the temperature is changed to a higher temperature, and a cold material such as iron ore is charged based on the temperature measurement result by the suprense, and the predetermined blowing is performed. The stop temperature was adjusted. For this reason, the high temperature period in the latter half of the blowing was long, and the amount of erosion of the refractory was large.

As will be shown in the examples described later, the method of the present invention makes it possible to adjust the temperature of the blow stop to a predetermined blow stop temperature without cooling material during a period from 5 minutes before the blow stop to 1 minute before the blow stop. Since the high-temperature period before blowing is shortened, the amount of erosion of the refractory can be greatly reduced.

[0040]

(Example 1) Using a 6-ton scale top-bottom blow test converter having a furnace port sealing device, a lance hole sealing device, and a closed type auxiliary material supply system as shown in FIG. The amount of decarburization was estimated by the method of the invention. A four-hole lance having a nozzle throat diameter of 12 mφ was used as the upper blowing lance, and the oxygen supply rate was 1500 to 1800 Nm ³ / h. For bottom blowing, oxygen and LPG as a cooling gas were supplied using a double tube tuyere. The oxygen flow rate was about 100 Nm ³ / h.

At the outlet side of the dry coarse dust collector behind the exhaust gas duct, an exhaust gas sample is continuously taken and CO, CO ₂
And while measuring the N ₂ concentration was bubbled N ₂ gas 60 Nm ³ / h in the hood nearest exhaust gas duct.

[C] When degassing about 4.2% of hot metal to a low-carbon region, the molten iron obtained from the exhaust gas information by the method of the present invention.
FIG. 4 shows the result of investigating the relationship between the estimated value of [C] and the actually measured value of molten iron [C], which was obtained by analyzing a molten iron sample spot by sublance during blowing.

The estimated value of the molten iron [C] is obtained by inputting data such as the exhaust gas composition analysis value and the flow rate of the blown N ₂ into a computer, performing a certain correction on the relationship of the above equation (1), and calculating the decarburization amount. The integrated value is obtained and calculated from the integrated value and the balance of Fe and C of the charge.

As shown in FIG. 4, the estimated value of molten iron [C] obtained by the method of the present invention was in good agreement with the measured value of the sample of Sublance.

(Example 2) In the same test converter as in Example 1, the amount of decarburization was estimated in the same manner as in Example 1, and a thermometer was arranged in the iron bath to continuously measure the temperature. Blowing control was performed based on the information on the amount of coal and the temperature.

The continuous temperature measurement was performed using a 5 mmφ Ar
This was performed by inserting an image fiber into the gas injection hole and obtaining a brightness image. The obtained brightness image includes not only the brightness of the molten steel seen through the Ar bubbles but also the brightness of the metal (mushroom) generated at the surrounding gas injection pipe and the outlet of the injection hole.
This was image-processed, and only the luminance information of the true molten steel portion was extracted and converted into temperature. The Ar flow rate was 6 Nm ³ / h.

Desiliconized and desulfurized C: 4.2%,
Si: 0.15%, Mn: 0.15%, P: 0.095
%, S: 0.011%, temperature: 1350 ° C., and a scrap with a hot metal ratio of 10% were charged into a converter, and then acid-supplied from an upper blowing lance to decarbonize. In response to the temperature change during the blowing acid,
Iron ore was added as cold material.

Iron ore 10 kg / t for 4 minutes from the start of blowing acid
Was added continuously to control the temperature at 1350-1450 ° C. In addition, for 2 minutes before blowing, control was performed without adding a cold material. The blow stop conditions are as follows: C: 0.06%, P: 0.015
%, Temperature: 1635 ° C, and quicklime basic unit is 31 kg
/ T and the wear of the refractory was extremely small.

On the other hand, in the comparative example, the temperature and carbon concentration of the molten iron were measured two to three times by a sublance during blowing in the same test converter, and blowing control was performed based on this information. Acid transfer conditions,
The bottom blowing conditions, the amount of hot metal charged and the amounts of scrap were almost the same as in the example, but the composition of the hot metal was C: 4.3% and Si: 0.4%.
14%, Mn: 0.16%, P: 0.098%, S:
0.010% and hot metal temperature was 1355 ° C.

The temperature measured 5 minutes after the start of blowing was 15
Since the temperature reached 70 ° C., iron ore was added and cooled. In addition, since the temperature measured 3 minutes before blowing was 1670 ° C., iron ore was added as a cold material. The blow stop condition is
C: 0.06%, P: 0.018%, temperature: 1658 ° C
However, the basic unit of quicklime was 48 kg / t, and the refractory was greatly worn.

[0051]

According to the present invention, it is possible to accurately and reliably perform temperature control and blowing end point control during blowing of a converter without performing measurement using a sublance. In particular, according to the method of the present invention, since the molten iron temperature can be accurately controlled during the entire blowing period, it is possible to improve the efficiency of the dephosphorization reaction at the beginning of blowing and to reduce the refractory wear at the end of blowing.

Further, since measurement by sublance is not required, the cost of the probe can be reduced, and
Equipment costs and work costs in the pressurized converter can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an example of an embodiment of the present invention described in claim 2;

FIG. 3 is an explanatory diagram showing an example of an embodiment of the present invention described in claim 3;

FIG. 4 is a diagram showing a relationship between an estimated value of molten iron [C] and an actually measured value in the present embodiment.

[Explanation of symbols]

1: Converter, 2: Iron bath, 3: Top blowing lance,
4: bottom blowing tuyere, 5: top blowing gas line, 6: top blowing gas flow control device, 7: hopper 8: cutout device, 9: charging chute, 10: temperature measuring tuyere, 1
1: purge gas supply line, 12: image fiber, 13: signal processing and temperature measuring device, 14: analysis tuyere, 15: purge gas supply line, 16: analysis fiber, 17: analysis device, 18: furnace port sealing device , 19: food, 20: sampling hole, 2
1: gas analyzer, 22: gas inlet, 23: flow meter, 24: lance hole sealing device

Claims (3)

[Claims] 1. An iron bath in an upper and lower blown converter, a thermometer is continuously arranged to measure a molten iron temperature, and based on the temperature information, an acid feed rate, a lance-to-metal surface gap, and a cooling auxiliary material. A method for controlling the blowing of a converter, comprising controlling one or more of the addition amounts to control the temperature of molten iron during blowing. 2. A thermometer and a carbon concentration measuring means are arranged in an iron bath in the top and bottom blown converter to measure the temperature and the carbon concentration of the molten iron, and the acid transfer is performed based on the information on the temperature and the carbon concentration. Blowing control of a converter characterized by controlling one or more of a speed, a lance-gap and a cooling auxiliary material addition amount to control a molten iron temperature and a carbon concentration during blowing. Method. 3. A thermometer is provided in an iron bath in the top and bottom blown converter to continuously measure molten iron temperature, and a furnace opening of the converter is sealed during blowing to prevent outside air from entering. Means for measuring the concentration of CO, CO ₂ and inert gas in the exhaust gas, and means for supplying a predetermined flow rate of the inert gas into the converter furnace or / and the exhaust gas duct upstream of the exhaust gas composition measurement point. The decarburization amount is estimated on the basis of the concentration of components in the exhaust gas and the flow rate of the inert gas. A method for controlling blowing of a converter, wherein one or more of the additional amounts of auxiliary raw materials are adjusted to control the molten iron temperature and carbon concentration during blowing.