JPH0219411A - Converter blow-refining method - Google Patents

Abstract

PURPOSE:To accurately assume molten metal temp. during blow-refining by actually measuring the temp. of the molten metal in a converter to set initial value and on the other hand, calculating variety of the molten metal temp. with oxidizing reaction quantity, etc., grasped from the detected values of components and quantity of furnace gas. CONSTITUTION:While blowing stirring gas into the molten metal in the converter 10 through a bottom blowing nozzle 14, oxygen jet is blown on the molten metal surface from a main lance 20 to execute blow-refining. The components and quantity of the furnace gas generated during this blow-refining are detected at any time with analyzers 34, 35 and a flow meter 36 set to a duct 28. Based on this detected results, actual quantity of the oxygen component in the converter 10 at this time and further, the oxidizing reaction quantity are grasped with a process computer 40. The variety of the molten metal temp. is calculated by using a mathematical model showing the relation between the molten metal temp. and the time from this oxidizing reaction quantity. On the other hand, the temp. of the molten metal in the converter is actually measured with sub-lance method. The actually measured value is set as the initial value and based on the above temp. variety, the molten metal temp. varying at every moment during blow-refining is assumed. By this method, the blow-refining in the converter can be accurately controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a converter blowing method for accurately determining the end point temperature of converter blowing.

[Prior Art] Recently, in converter blowing, dynamic control has been adopted in which blowing conditions are computer-controlled based on various measurement information during blowing. In blowing using dynamic control, in order to control the end point, a sublance (intermediate sublance) is immersed in the molten metal during blowing to directly measure the molten metal temperature and molten metal carbon concentration [C], and the blowing is performed based on this measured temperature. The conditions are appropriately controlled to control the end point temperature and components. After that, another sub-lance (end point sub-lance) is inserted into the molten metal, the temperature and [C] are measured again, and the blowing is finished when the molten metal temperature matches the predetermined tapping temperature (
Stop blowing).

The conventional converter blowing method predicts the transition of the decarburization reaction, which is a dynamic model, based on the molten metal temperature obtained in the intermediate sublance and [C], and calculates the temperature rise of the molten metal from the predicted amount of the decarburization reaction. presume. Then, blowing is appropriately controlled based on the estimated temperature rise amount so that the molten metal temperature (end point temperature) at the end of blowing falls within the target tapping temperature range.

[Problem to be solved by the invention] However, in the conventional converter blowing method, [C] is high in the early and middle stages of blowing, so the temperature dependence of the molten metal due to decarburization reaction is strong; When it reaches , the temperature dependence weakens, and a discrepancy tends to occur between the predicted value due to the decarburization reaction and the actual value. For this reason, the end point temperature may deviate greatly from the tapping temperature, and the end point accuracy rate decreases. For this reason,
It is necessary to directly observe the reaction in the furnace even after the intermediate sublance measurement, which has the drawback of extending the blowing time and increasing operating costs.

This invention has been made in view of the above circumstances, and provides a converter blowing method that can improve the end point accuracy without directly observing the reaction in the furnace even after the intermediate sublance has settled down. The purpose is to provide.

[Means for Solving the Problems] The converter blowing method according to the present invention detects the components and amounts of furnace gas generated during converter blowing at any time, and determines the oxygen components in the converter at that time from the detection results. The amount of oxidation reaction in the furnace is determined, and the amount of change in molten metal temperature is calculated using a predetermined mathematical model that expresses the relationship between the amount of oxidation reaction, molten metal temperature, and time. The method is characterized in that the temperature of the molten metal in the converter is actually measured and used as an initial value, and the molten metal temperature that changes momentarily during blowing is estimated based on this initial value and the amount of temperature change.

[Operation] In the converter blowing method according to the present invention, the components and amounts of the furnace gas are measured at any time, the amount of oxygen present in the furnace gas is ascertained, and the oxygen content in the gas is determined using the following formula (1). The amount of oxygen accumulated in the furnace wo2 is determined from the amount present.

... (1) However, the symbol S is during sublance, the symbol t is t seconds after the intermediate sublance measurement, and INPUT O2 is oxygen entering the furnace (spraying is oxygen gas, auxiliary raw material, bottom blowing gas). , intruding air), and 0UTPUT 02 indicate the total amount of oxygen (exhaust gas, ejected gas) coming out of the furnace.

Next, using the following equation (2), the rate of change in the amount of accumulated oxygen dWo2
Find /d02.

dWO2/ do2= aX 11 exp (W
o2/b)1...(2) However, symbols a and b each indicate a coefficient.

Next, the amount of temperature increase ΔT of the molten metal is calculated using a mathematical model shown in equation (3) below.

10B X Ws L A Q +C1d02-D
X Wco Lo -(
3) However, the symbol WSLACI is the initial slag amount, and the symbol WC
OLD indicates the amount of coolant, and symbols A, B, and CD indicate coefficients, respectively.

On the other hand, the molten metal temperature Ts is actually measured by intermediate sublance measurement, and the molten metal temperature TT after t seconds has elapsed from the sublance measurement is determined from the relationship shown in equation (4) below.

TT""TS+ΔT - (4) From this, the elapsed time t until the temperature TT matches the predetermined tapping temperature T is estimated.

[Embodiments] Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.

The converter 10 is a composite blowing furnace configured to blow stirring gas into the molten metal 12 through a bottom blowing nozzle 14 and to blow an oxygen jet from a main lance 20 onto the surface of the molten metal. Piping 16 and main lance 2 communicating with bottom blowing nozzle 14
Flowmeters 18 and 24 are installed in the piping 22 communicating with o.
are provided, each connected to the input side of the process computer 4o. The computer 4o has a memory that stores input data, an arithmetic unit that executes various operations, and a CPU (central processing unit) that sequentially retrieves and processes data stored in the memory, and collects various process data. Optimum control conditions for blowing are determined based on mathematical models corresponding to predetermined static models and dynamic models, and optimal control commands are issued to various devices.

A hood 26 of a duct 28 is provided to cover the charging port of the converter 10, and gas generated within the converter is guided through the duct 28 to an exhaust gas treatment device (not shown). A chute 30 is attached to the duct 28 near the converter charging inlet, and the auxiliary raw material weighed by the weigher 32 is transferred to the chute 30.
It is cut out into the duct 28 through the duct 28, and further falls into the converter. On the other hand, a gas analyzer 34 and a mass spectrometer 35 are installed at the top of the duct 28,
The components and mass of exhaust gas are detected.

Further, an exhaust gas flow meter 36 is provided at the throttle at the bottom of the duct to detect the flow rate of exhaust gas.

In addition, the weighing device 32. Gas analyzer 34. Each of the mass spectrometer 35 and the flow meter 36 is connected to the input side of the computer 40.

Additionally, a sublance device (not shown) is installed above the converter 10.
is provided, and when the sub-lance is lowered, the tip of the sub-lance is inserted into the converter from the charging port and immersed in the molten metal 12. Incidentally, a probe is attached to the tip of the sublance so that the molten metal's lH degree and carbon concentration [C] can be immediately detected.

Next, a case will be described in which the end point temperature is estimated in this embodiment.

When the final stage of blowing is reached and decarburization of the molten metal progresses, the intermediate sublance is lowered to determine the molten metal temperature TS and [C],
This is input into the computer 40.

The exhaust gas components, the mass of each component, and the exhaust gas flow rate are detected, and these detected values are also input into the computer 40. The amount of (OUTPUT o2) is calculated from these data. On the other hand, from the amount of oxygen supplied, the components and input amount of auxiliary raw materials, the amount of bottom blown gas, and the amount of intruding air, (IN'PUT
o2) Find the quantity, and (OUTPUT 02) f
The accumulated oxygen amount WO2 is calculated from fl. Based on this, the rate of change in the amount of stored oxygen dWO2/dO2 is determined. Furthermore, the amount of temperature increase ΔT after t seconds from the time of intermediate sub-lancing is calculated, and the time t at which the difference between the target tapping temperature T and the actual temperature Ts during sub-lancing matches the amount of temperature rise ΔT is calculated, and The time when time t has elapsed is estimated to be the end point time.

FIG. 2 is a graph showing the accuracy of the accuracy of the estimated temperature at the end point of a composite blowing furnace, with the actual temperature on the horizontal axis and the estimated temperature on the vertical axis.

The circles in the figure are plots of the results of each charge blown using the method of the example.

As is clear from the figure, all of the actual temperatures are within the range of plus or minus 10°C of the estimated temperature, and the temperature deviation can be reduced from the conventional 7 to 8°C to approximately 4.5°C. was able to be made smaller. For this reason, the accuracy rate for falling within a range of plus or minus 10 degrees Celsius of the estimated temperature has been improved from about 94% in the past to nearly 100%.

[Effects of the Invention] According to the present invention, the molten metal temperature can be continuously and highly accurately estimated online without directly observing the reaction in the furnace even after the intermediate sublance measurement. For this reason,
The end point accuracy rate can be improved, and the productivity of converter operation can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining a converter blowing method according to an embodiment of the present invention, and FIG. 2 is a graph diagram showing the effects of the present invention. 10; converter, 12; molten metal, 14; bottom blowing nozzle, 16.
22. Pipe, 18, 24.36; Flow meter, 20; Lance,
26; Hood, 28; Duct, 30; Shooter, 32;
Weighing device, 34, 35; Minute meter, 40; Process computer applicant patent attorney Takehiko Suzue

Claims (1)

[Claims] Detects the components and amount of furnace gas generated during converter blowing at any time,
The amount of oxygen present in the converter at that time is determined from the detection results, the amount of oxidation reaction in the furnace is determined, and the molten metal is calculated using a predetermined mathematical model that expresses the relationship between the amount of oxidation reaction, molten metal temperature, and time. While calculating the amount of change in temperature, the temperature of the molten metal in the converter is actually measured using the sublance method, and this is used as the initial value, and the molten metal temperature, which changes moment by moment during blowing, is estimated based on this initial value and the amount of temperature change. A converter blowing method characterized by: