FURNACE SLAG AMOUNT ESTIMATION DEVICE, FURNACE SLAG AMOUNT ESTIMATION METHOD, AND MOLTEN STEEL PRODUCTION METHOD

A furnace slag amount estimation device (1) includes: an input unit (11) configured to receive input data including furnace shape data for a converter, data on components and temperatures of molten metal and slag before start of or during blowing treatment, and slag height data in a furnace of the converter; a slag bulk density calculation unit (13) configured to calculate a slag bulk density after the converter is tilted, using the input data and a model; a slag volume calculation unit (14) configured to calculate a slag volume in the furnace after the converter is tilted, using the slag height data after the converter is tilted, the furnace shape data, and a model; and a slag weight calculation unit (15) configured to calculate a slag weight in the furnace after the converter is tilted and slag is discharged, using the calculated slag bulk density and the calculated slag volume.

TECHNICAL FIELD

The present disclosure relates to a furnace slag amount estimation device, a furnace slag amount estimation method, and a molten steel production method. The present disclosure relates, in particular, to a furnace slag amount estimation device, a furnace slag amount estimation method, and a molten steel production method by which a furnace slag amount in refining equipment in the iron and steel industry is estimated.

BACKGROUND

At steelworks, the components and the temperature of hot metal tapped out of a blast furnace are adjusted in refining equipment, such as pretreatment equipment, converters, or secondary refining equipment. The converters are a process of blowing oxygen into the furnaces, so as to remove impurities from molten metal and raise the temperature, and they play a very important role, for example, in controlling steel quality and rationalizing refining costs. In recent years, the development of hot metal pretreatment treatment methods (desiliconization treatment and dephosphorization treatment) in converters has progressed, and a method is becoming popular in which a converter is tilted after blowing treatment so as to discharge slag in the furnace out of the furnace (slag-removal), and then the converter is turned upright so as to perform continuing blowing treatment. In this method, the charge amount of auxiliary raw materials, such as lime, is adjusted so as to obtain desired components of slag in blowing (secondary blowing) after the slag-removal, based on the components of slag at the end of blowing (primary blowing) before the slag-removal and a furnace slag weight after the slag-removal. Conventionally, the furnace slag weight after the slag-removal has been calculated by an operator by visually estimating the slag amount discharged out of the furnace by the slag-removal, or by weighing a pot that receives the slag discharged out of the furnace by the slag-removal and measuring the weight of the discharged slag, to thereby determine the charge amount of auxiliary raw materials in the secondary blowing. However, visual estimation is inaccurate because slag is bubbled during blowing treatment due to CO gas or the like generated by reaction in the furnace, and its bulk density varies significantly. Furthermore, it is difficult to prevent slag from overflowing from the pot during the slag-removal process. Moreover, the effects of metal spilled during the slag-removal and iron droplet in slag cannot be eliminated, and the accuracy of measuring the slag weight by a weighing instrument is not always high. The low accuracy of estimating the furnace slag weight after the slag-removal tends to lead to excessive charging of auxiliary raw materials in the secondary blowing, thus resulting in a lower cost efficiency and a lower iron yield rate.

Patent Literature (PTL) 1 therefore describes a method of estimating calming properties of slag in a furnace by measuring a slag height in the furnace multiple times before slag-removal, and estimating a furnace slag weight after the slag-removal, based on the calming properties and a tilt pattern of the converter during the slag-removal.

CITATION LIST

Patent Literature

SUMMARY

Technical Problem

In PTL 1, however, the furnace slag weight after the slag-removal is calculated, based on a slag volume in the furnace that has been geometrically calculated from the calming properties during the slag-removal and a tilt angle of the converter. For example, when the shape of a furnace throat of the converter changes due to wear of refractory bricks, attachment of skull, or the like, the relationship between the tilt angle of the converter and the furnace slag volume changes, and the estimated value of the furnace slag weight deviates from the actual value. In addition, the shape in the vicinity of the furnace throat of the converter may change due to attachment of skull or the like, even during one time of blowing treatment. It is therefore difficult to obtain accurate shape information at all times. Thus, it is difficult to estimate the furnace slag weight after the slag-removal with high accuracy by such a method of geometrically calculating the furnace slag volume from the tilt angle of the converter.

It would be helpful to provide a furnace slag amount estimation device, a furnace slag amount estimation method, and a molten steel production method by which a furnace slag weight after slag-removal can be estimated with high accuracy.

Solution to Problem

A furnace slag amount estimation device according to an embodiment of the present disclosure is a furnace slag amount estimation device that estimates a slag weight remaining inside a converter in blowing treatment that includes a process of tilting the converter so as to discharge slag in a furnace out of the furnace, the furnace slag amount estimation device including:an input unit configured to receive input data including furnace shape data for the converter, data on components and temperatures of molten metal and slag before start of or during the blowing treatment, and slag height data in the furnace of the converter;a slag bulk density calculation unit configured to calculate a slag bulk density after the converter is tilted and the slag is discharged, using the input data and a slag bulk density estimation model;a slag volume calculation unit configured to calculate a slag volume in the furnace after the converter is tilted and the slag is discharged, using the slag height data after the converter is tilted and the slag is discharged, the furnace shape data, and a slag volume estimation model; anda slag weight calculation unit configured to calculate the slag weight in the furnace after the converter is tilted and the slag is discharged, using the calculated slag bulk density and the calculated slag volume.

A furnace slag amount estimation method according to an embodiment of the present disclosure isa furnace slag amount estimation method to be executed by a furnace slag amount estimation device that estimates a slag weight remaining inside a converter in blowing treatment that includes a process of tilting the converter so as to discharge slag in a furnace out of the furnace, the furnace slag amount estimation method including:an input step of receiving input data including furnace shape data for the converter, data on components and temperatures of molten metal and slag before start of or during the blowing treatment, and slag height data in the furnace of the converter;a slag bulk density calculation step of calculating a slag bulk density after the converter is tilted and the slag is discharged, using the input data and a slag bulk density estimation model;a slag volume calculation step of calculating a slag volume in the furnace after the converter is tilted and the slag is discharged, using the slag height data after the converter is tilted and the slag is discharged, the furnace shape data, and a slag volume estimation model; anda slag weight calculation step of calculating the slag weight in the furnace after the converter is tilted and the slag is discharged, using the calculated slag bulk density and the calculated slag volume.

A molten steel production method according to an embodiment of the present disclosure includesproducing molten steel, by determining a charge amount of auxiliary raw materials in secondary blowing, based on the slag weight in the furnace calculated by the above furnace slag amount estimation method, and performing refining operation.

Advantageous Effect

According to the present disclosure, the furnace slag amount estimation device, the furnace slag amount estimation method, and the molten steel production method by which the furnace slag weight after slag-removal can be estimated with high accuracy are provided.

DETAILED DESCRIPTION

Hereinafter, a furnace slag amount estimation device, a furnace slag amount estimation method, and a molten steel production method according to an embodiment of the present disclosure will be described with reference to the drawings. Here, the furnace slag amount means a slag weight remaining inside (in the furnace of) a converter.

FIG.1is a schematic diagram illustrating a configuration of a furnace slag amount estimation device1according to an embodiment of the present disclosure. In the present embodiment, the furnace slag amount estimation device1is used as part of equipment for producing molten steel. The equipment for producing molten steel includes refining equipment, and a blowing control system that includes the furnace slag amount estimation device1.

As illustrated inFIG.1, the refining equipment includes a converter100, a lance103, a hopper104above the furnace, and a slag height measurement device105. The lance103is arranged above molten metal101in the converter100. High-pressure oxygen is ejected from a tip of the lance103toward the molten metal101located below. The high-pressure oxygen oxidizes impurities in the molten metal101and incorporates them into slag102(refining treatment). Auxiliary raw materials, including lime, carburization materials, and coolants, are charged into the converter100from the hopper104above the furnace or the like and incorporated into the molten metal101and the slag102.

The slag height measurement device105is set at the top of the converter100and measures the distance from a furnace throat of the converter100to a surface of the slag102contained in the converter100. The slag height measurement device105may be, for example, a microwave rangefinder. The microwave rangefinder may measure the distances to the furnace throat of the converter100and to the surface of the slag102in the converter100, by converting time it takes to emit microwaves and receive reflected waves from the furnace throat of the converter100and from the surface of the slag102in the converter100into distances. The slag height may be measured at any time or continuously. Signals indicating measurement results of the slag height measurement device105are transmitted to a control terminal10.

Here, in refining using the converter100, the processes of “loading,” “primary blowing,” “slag-removal,” “secondary blowing,” and “tapping” are performed in sequence during a single charge. In the “loading” process, raw materials, such as hot metal, are loaded into the converter100. In the “primary blowing” process, auxiliary raw materials are charged into the converter100for the purpose of, for example, desiliconization, or desiliconization and dephosphorization, and blowing is performed. In the “slag-removal” process, part of the slag102with a relatively low basicity (CaO concentration/SiO2concentration) generated in the primary blowing is discharged out of the furnace by slag-removal treatment. In the “secondary blowing” process, auxiliary raw materials are charged into the converter100for the purpose of dephosphorization and/or decarburization, for example. In the “tapping” process, the molten metal101is tapped out. Normally, these processes are repeated with multiple charges in the refining. The slag102from the secondary blowing of the nthcharge that remains in the converter100may be carried over to the (n+1)thcharge.

Some of the processes will be explained more concretely with reference to the refining equipment ofFIG.1. After the primary blowing ends, the lance103is withdrawn to the top of the converter100, and the slag-removal treatment is conducted, by tilting the converter100so as to discharge the slag102in the furnace out of the furnace. The slag-removal treatment ends immediately before the molten metal101is discharged, and after the converter100is returned to the upright position, the lance103is again installed on top of the molten metal101, and the secondary blowing is started. Blowing conditions, including the amount of auxiliary raw materials to be charged from the hopper104above the furnace or the like, in the secondary blowing are determined based on results of the primary blowing and results of the slag-removal treatment. The furnace slag amount estimation device1is a device that estimates the weight of the slag102in the converter100after the slag-removal treatment.

The blowing control system includes the control terminal10, a display device20, and the furnace slag amount estimation device1as main components. The control terminal10may be configured by an information processing device, such as a personal computer or a workstation. The control terminal10collects track record data regarding blowing treatment and slag-removal treatment, and controls blowing conditions, including the amount of auxiliary raw materials to be charged from the hopper104above the furnace or the like, so that the temperature and the component concentrations of the molten metal101and the composition of the slag102are within desired ranges. The display device20may be configured by a liquid crystal display (LCD) or cathode ray tube (CRT) display, for example. The display device20may display calculation results or the like that are output from the furnace slag amount estimation device1.

The furnace slag amount estimation device1is configured by an information processing device, such as a personal computer or a workstation. The furnace slag amount estimation device1includes an input unit11, a database12, a slag bulk density calculation unit13, a slag volume calculation unit14, a slag weight calculation unit15, and an output unit16.

The input unit11is an input interface that receives various types of information related to the refining equipment. The input unit11may include, for example, a keyboard, a mouse, a pointing device, a data receiver, and/or a graphical user interface (GUI). The input unit11receives track record information, parameter setting values, or the like from the outside and writes the information into the database12and transmits it to the slag bulk density calculation unit13and the slag volume calculation unit14. Input data is input into the input unit11from the control terminal10. The input data includes furnace shape data, which indicates measurement results or calculation results regarding the furnace shape of the converter100. The input data includes data that indicates measurement results or calculation results regarding the components and the temperature of the molten metal101and the slag102before the start of or during blowing treatment. The input data also includes slag height data, which indicates measurement results of the slag height in the furnace of the converter100after slag-removal treatment. Additionally, the input unit11can be used for manual data input (manual input) by, for example, an operator of the refining equipment. Parameter setting values for a model formula may be input manually.

The database12stores various measurement results and calculation results in blowing treatment and slag-removal treatment, models and parameters for calculating the furnace slag amount, and estimation results of the furnace slag amount. The database12is configured, for example, by a storage device, such as memory or a hard disk drive. The storage device may further store computer programs. Various types of information input through the input unit11and estimation results of the furnace slag amount that have been calculated by the slag weight calculation unit15are transmitted to the database12. The models and parameters stored in the database12are to be used by the slag bulk density calculation unit13and the slag volume calculation unit14.

Using measurement results regarding the height of the slag102in the furnace after the slag-removal treatment (slag height data), furnace shape data, and a slag volume estimation model, the slag volume calculation unit14calculates the volume of the slag102after the slag-removal treatment. The slag volume calculation unit14transmits the calculated volume of the slag102after the slag-removal treatment to the slag weight calculation unit15.

Using the slag bulk density after the slag-removal treatment that has been calculated by the slag bulk density calculation unit13and the slag volume after the slag-removal treatment that has been calculated by the slag volume calculation unit14, the slag weight calculation unit15calculates the slag weight in the furnace after the slag-removal treatment. The slag weight calculation unit15transmits the calculated furnace slag amount (weight of the slag102remaining in the furnace after the slag-removal treatment) to the output unit16.

The output unit16transmits the furnace slag amount that has been calculated by the slag weight calculation unit15to the control terminal10and to the database12. In secondary blowing, various manipulated variables are determined and operating conditions are changed, based on calculation results output from the furnace slag amount estimation device1. The output unit16also has the function of transmitting the information calculated by the furnace slag amount estimation device1to the display device20, so that the calculation results output from the furnace slag amount estimation device1can be displayed.

FIG.2is the flowchart illustrating processing of the furnace slag amount estimation method according to an embodiment of the present disclosure. The flowchart ofFIG.2starts at a time when primary blowing ends. That is, after the primary blowing ends, furnace slag amount estimation processing proceeds to Step S1.

In processing of Step S1, after slag-removal treatment ends, the height of the slag102in the converter100is measured. The height of the slag102may be measured after the converter100is returned to the upright position, so as to make it easy to calculate the volume as will be described later. The height of the slag102in the furnace may be obtained based on a single measurement value, but is preferably obtained as a representative value of the height of the slag102over any given period of time, by averaging multiple measurement values that vary in time and space. The measured height of the slag102in the furnace is transmitted to the input unit11. This completes the processing of Step S1, and the furnace slag amount estimation processing proceeds to Step S2.

In processing of Step S2, the input unit11acquires data on the blowing treatment, the slag-removal treatment, or the like. More specifically, the input unit11acquires input data, including furnace shape data for the converter100, data on the components and the temperatures of the molten metal101and the slag102before the start of or during the blowing treatment, and slag height data in the furnace of the converter100. Step S2can be referred to as an input step. Here, the furnace shape data included in the input data may be generated based on measurements of the converter100before the “loading” process, that is, those of the converter100before raw materials are loaded, and may be acquired from the control terminal10together with other data in Step S2. The input unit11also transmits track record data, parameter setting values, or the like to the database12, the slag bulk density calculation unit13, and the slag volume calculation unit14. This completes the processing of Step S2, and the furnace slag amount estimation processing proceeds to Step S3.

In the formula, i denotes a parameter that identifies the item of explanatory variables obtained from results of the primary blowing treatment and results of the slag-removal treatment. vi denotes the explanatory variables. Aidenotes a coefficient corresponding to each explanatory variable. The explanatory variables include at least the tilt angle at which the slag102begins to be discharged from the furnace throat as the converter100is tilted in the slag-removal treatment, and slag-removal treatment time, which is time taken to execute the slag-removal treatment. The explanatory variables may further include the maximum tilt angle during the slag-removal treatment, a calculated value of the weight of the slag102in the furnace at the end of the primary blowing, a calculated value of slag basicity (CaO concentration/SiO2concentration), a calculated value of the iron concentration in the slag, a calculated value of iron flushing weight in the slag, and the like. Here, when the slag begins to flow out by tilting the furnace body, the slag height is almost equal to a furnace height. The volume of the slag in the furnace, which is closely related to the bulk density, can be calculated from the tilt angle of the furnace body at which the slag begins to flow out and the furnace shape data. It is therefore important that the explanatory variables include at least the tilt angle at which the slag102begins to be discharged from the furnace throat. Furthermore, the slag102before slag-removal treatment contains a large amount of air bubbles and has a relatively low bulk density, and during the slag-removal treatment, the air bubbles are often released and the bulk density increases. Accordingly, the longer the slag-removal treatment time, the higher the bulk density of the slag102after the slag-removal treatment tends to be. It is therefore important that the explanatory variables include at least the slag-removal treatment time.

The slag bulk density estimation model after the slag-removal is not limited to the aforementioned linear combination model formula, and a machine learning model or the like may also be used.

Here, the machine learning model can be built based on past data stored in the database12prior to operation. Explanatory variables can be obtained from observable measured values and analytical values, calculated values based on these, or the like. The slag bulk density may be obtained from a calculation result of the volume of slag remaining in the furnace, a measured value of the furnace slag amount, or the like, as will be described below.

The measured value of the furnace slag amount may be obtained from the difference between the furnace slag amount before the slag-removal, which is calculated based on the charge amount of auxiliary raw materials during the primary blowing, and the furnace slag amount after the slag-removal, which is measured by the weighing instrument. The furnace slag amount may also be obtained, by calculating backwards a removed slag weight, from analytical values of the components of slag after the slag-removal and the charge amount of auxiliary raw materials during the primary blowing.

As described above, various machine learning models can be built using not only linear regression models but also objective variables and explanatory variables, which are track record values, as teacher data. A highly accurate model based on any method may be used.

The slag bulk density calculation unit13transmits the calculated bulk density of the slag102after the slag-removal treatment to the slag weight calculation unit15. This completes the processing of Step S3, and the furnace slag amount estimation processing proceeds to Step S4.

In processing of Step S4, the slag volume calculation unit14calculates the volume of the slag102after the slag-removal treatment using the slag height data for the slag102in the furnace after the slag-removal treatment, the furnace shape data, and a slag volume estimation model. Step S4can be referred to as a slag volume calculation step. In the present embodiment, the volume (Vs) of the slag102in the furnace after the slag-removal treatment is calculated by the slag volume estimation model. The slag volume estimation model illustrated in Formula (2) below uses the height (Hslag) of the slag102in the furnace, the furnace shape data, a measured value (Wmetal) of the weight of the molten metal101, and the specific gravity (Pmetal) of the molten metal101.

Here, V (Hslag) denotes the total volume of the molten metal101and the slag102in the converter100that is determined from the height (Hslag) of the slag102in the furnace and the furnace shape data. V (Hslag) may be obtained by the integral method based on the furnace shape data, as a furnace volume from a bottom of the furnace to the height of the slag102. Alternatively, calculated values of V (Hslag) corresponding to heights from the bottom of the furnace may be stored in the database12in advance, based on the furnace shape data, and V (Hslag) may be obtained by selecting a calculated value stored in the database12that corresponds to the height of the slag102. Here, the measured value of the weight of the molten metal101and the specific gravity are obtained from measurement results or calculation results of the components of the molten metal101before the start of or during the blowing treatment that are included in the input data. Additionally, the furnace shape data preferably include furnace profile information measured by a laser rangefinder or the like. For example, the inside of the furnace before the primary blowing starts may be measured by the laser rangefinder, to thereby obtain distance data from a centerline of the furnace body at predetermined intervals in a vertical direction and at predetermined angles around the centerline. The acquired distance data is stored in the database12as a set of points in a polar coordinate system, so as to be used as the furnace body profile information to calculate the furnace volume.

When the furnace body is tilted, the tilt angle may be included as an input and the height of the slag102may be corrected based on the tilt angle before calculating the volume.

The slag volume estimation model is not limited to the above formula, and a machine learning model or the like may also be used.

Here, the furnace shape data may be updated at appropriate times by new measurements, so as to reflect changes in the shape or the like. The furnace shape data may also be corrected using the amount of wear in the furnace that is estimated based, for example, on the count of times the converter100has been used. The slag volume calculation unit14transmits the calculated volume of the slag102after the slag-removal treatment to the slag weight calculation unit15. This completes the processing of Step S4, and the furnace slag amount estimation processing proceeds to Step S5.

In processing of Step S5, the slag weight calculation unit15calculates the weight of the slag102after the slag-removal treatment. The weight of the slag102after the slag-removal treatment is calculated, by multiplying the estimated value of the bulk density of the slag102after the slag-removal treatment that has been calculated by the slag bulk density calculation unit13by the volume of the slag102after the slag-removal treatment that has been calculated by the slag volume calculation unit14. Step S5can be referred to as a slag weight calculation step.

The output unit16transmits the weight of the slag102after the slag-removal treatment that has been calculated by the slag weight calculation unit15to the database12. The output unit16also transmits the weight of the slag102after the slag-removal treatment to the control terminal10. The control terminal10may determine conditions for secondary blowing treatment, based on results of the slag-removal treatment and results of the primary blowing treatment, including the obtained weight of the slag102. The output unit16also transmits the weight of the slag102after the slag-removal treatment to the display device20. An operator can change the conditions for the secondary blowing treatment in accordance with the weight of the slag102after the slag-removal treatment that is displayed on the display device20. This completes the processing of Step S5, and the furnace slag amount estimation processing is completed.

Based on the slag weight remaining inside the converter100that is estimated by the above furnace slag amount estimation method, optimal slag design in the secondary blowing can be made. That is, based on the estimated furnace slag amount, the charge amount of auxiliary raw materials is determined so as to obtain an optimum basicity (CaO concentration/SiO2concentration), and refining operation (decarburization blowing) is conducted, to thereby produce good molten steel. Thus, based on the slag weight in the furnace calculated by the above furnace slag amount estimation method, a favorable molten steel production method can be realized.

As described above, according to the furnace slag amount estimation device1, the furnace slag amount estimation method, and the molten steel production method according to the present embodiment, a slag weight in the furnace after slag-removal can be calculated using a calculated value of slag bulk density after the slag-removal, and a furnace slag volume that has been calculated from measurement results regarding a slag height. This makes it possible to eliminate variation factors, such as changes in the shape in the vicinity of a furnace throat of a converter, and to estimate the furnace slag weight after the slag-removal with high accuracy.

Although an embodiment of the present disclosure has been described based on the drawings and examples, it is to be noted that various modifications and changes may be easily made by those skilled in the art based on the present disclosure. Accordingly, such modifications and changes are included within the scope of the present disclosure. For example, functions or the like included in each component, each step, or the like can be rearranged without logical inconsistency, and a plurality of components, steps, or the like can be combined into one or divided. An embodiment according to the present disclosure can also be implemented as a program that is executed by a processor included in a device, or as a storage medium in which the program is recorded. It is to be understood that these are included within the scope of present disclosure.

For example, in the present embodiment, the furnace slag amount estimation method that is to be performed after slag-removal treatment without tapping is described. Here, in a case in which tapping is performed after blowing treatment and some of the slag in the furnace is carried over to the next blowing treatment, the furnace slag amount can also be estimated by the same furnace slag amount estimation method, by setting the weight of molten metal in the furnace to 0.

REFERENCE SIGNS LIST