JP6515385B2 - Hot metal pretreatment method and hot metal pretreatment control device - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a hot metal pretreatment method and hot metal pretreatment control apparatus for determining the end point of desiliconization treatment in hot metal pretreatment using a converter.

  In recent years, the quality improvement of steel materials has been realized by the improvement of the technology of hot metal pre-treatment using a converter. Components to be subjected to the hot metal pretreatment include components related to the quality of steel materials such as P and Si. Among them, dephosphorization treatment to remove P from hot metal is an important process in hot metal pretreatment.

  The dephosphorization reaction formula is shown in the following formula (1). In the following formula (1), “[substance X]” indicates substance X in hot metal and “(substance Y)” indicates substance Y in slag.

In order to promote the dephosphorization reaction shown in the above formula (1) to remove P efficiently, it is necessary to increase the CaO concentration in the slag and the FeO concentration in the slag. Further, in order to fix the _P 2 _{O 5} produced in the slag, it is necessary to control the slag basicity of _{((CaO) / (SiO 2} )) in an appropriate range. An appropriate range of the basicity of slag is known to be, for example, 1.0 to 3.0, and the larger the basicity, the more the dephosphorization reaction is promoted.

On the other hand, in recent years, the concentration of Si contained in the hot metal discharged from the blast furnace has become high. It is believed that this is because the structure of the blast furnace has changed and the use of iron ore containing a large amount of Si component has increased. When oxygen is supplied to the hot metal in the converter during blowing, from a thermodynamic point of view, Si in the hot metal is preferentially oxidized over other components. Therefore, when the hot metal Si concentration is high, the amount of SiO ₂ generated is also large. In that case, in order to control the basicity of the above-mentioned slag in an appropriate range in order to promote dephosphorization reaction, more CaO containing materials are needed, and the amount of generation of slag also increases. Therefore, the procurement cost of the CaO-containing substance is increased. Moreover, the processing cost of slag also increases with the increase in the usage-amount of a CaO containing material.

  Therefore, a technology has been proposed in which the silicon removal treatment is performed in advance using a converter before the phosphorus removal treatment is performed. Specifically, a technique is proposed in which the concentration of molten silicon Si is reduced in advance before the dephosphorization treatment by performing a desiliconization treatment using blowing in a converter as a step prior to the dephosphorization treatment. Thereby, the input amount of the CaO-containing substance can be reduced. In order to appropriately reduce the input amount of the CaO-containing material, it is required to appropriately predict a point in time when the silicon removal treatment ends (hereinafter, referred to as “point of termination of silicon removal treatment”). That is, it is necessary to determine with high accuracy the concentration of molten iron Si reduced by the silicon removal treatment.

  In order to solve the above problems, in Patent Document 1 below, the FeO concentration in the slag during the silicon removal treatment is estimated, and a specified operation is performed according to the estimated FeO concentration, and a specified time from the start of the silicon removal treatment A technique is disclosed to control the concentration of molten Si within a specific range by adjusting the concentration of FeO over time. Further, in Patent Document 2 below, assuming that the ratio of the amount of oxygen used for oxidation of Si in the molten metal in the silicon removal treatment is 80% of the amount of acid supplied by blowing, all the Si in the molten metal is removed There is disclosed a technique for calculating the amount of acid feed necessary for silicidation.

JP, 2013-13683, A JP, 2014-141696, A

  However, although the time for which the silicon removal treatment is carried out is fixed in Patent Document 1 mentioned above, the silicon removal rate is also considered to be different depending on the structure of the converter and the equipment for blowing and blowing. It is considered that the effects of the disclosed technology can not be exhibited. In addition, no specific adjustment amount for adjusting the FeO concentration in the slag is disclosed. Therefore, there remain questions about the realization of the silicon removal treatment based on Patent Document 1 above. Moreover, in the said patent document 2, the ratio of the amount of oxygen used for the oxidation of Si is being fixed with 80% of the amount of acid supplies by blowing. However, the ratio of the amount of oxygen used for the oxidation of Si in the hot metal in the desiliconization treatment is not constant, and may vary greatly depending on the charge. Therefore, assuming that the amount of oxygen used for oxidizing Si in the molten metal is a fixed value, there is a possibility that the concentration of molten Si after the silicon removal treatment may vary.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to determine with high accuracy the end point of desiliconization treatment in hot metal pretreatment using a converter. It is an object to provide a possible new and improved hot metal pre-treatment method.

In order to solve the above-mentioned problems, according to one aspect of the present invention, there is provided a method of hot metal pre-treatment by blowing using a converter, comprising an initial concentration of a hot metal component containing at least Si, Fe and C. Based on the molten iron data acquisition step for acquiring data, the above-mentioned initial molten iron data acquired, and time-series exhaust gas data including the components and flow rates of the exhaust gas discharged from the converter, the upper blow lance supplies to the molten iron Model at the interface between the molten metal and the slag which progresses in a different area from the mathematical model expressing the fire point reaction which is the oxidation reaction between the molten iron and the molten iron and the area at which the fire point reaction proceeds use in order to express the slag metal interface reaction, a complex reaction models and mathematical model based on competitive reaction model in which the fire point reaction were considered are combined is And the estimation step of sequentially estimating the Si concentration in molten metal and the Si equilibrium concentration at the slag metal interface, and the time when the difference between the above-estimated molten metal Si concentration and the Si equilibrium concentration is less than or equal to a predetermined threshold. There is provided a hot metal pre-treatment method including the silicon removal processing end determination step of determining the end point of the silicon removal processing.

  In the hot metal pretreatment method, the predetermined threshold may be 0.01%.

  The hot metal pre-treatment method stops the blowing when it is determined that the silicon removal treatment is completed, and discharges part or all of the slag generated in the converter, and thereafter The blowing may be resumed.

  In the composite reaction model, the concentration change of the molten metal component is caused by the mass transfer of the molten metal component from the molten metal to the slag metal interface, and the molten metal component from the fire point region to a region different from the fire point region. It may be calculated based on the mass transfer of

  In the composite reaction model, the concentration change of the slag component is generated by the mass transfer of the slag component from the slag to the slag metal interface which proceeds by the slag metal interface reaction, and the oxidation reaction in the fire point region. It may be calculated based on the mass transfer of the slag component contained in the oxide.

In order to solve the above problems, according to another aspect of the present invention, there is provided a hot metal pretreatment control device for controlling hot metal pretreatment by blowing with a converter, comprising at least Si. Based on time series exhaust gas data including a hot metal data acquisition unit for obtaining initial hot metal data including initial concentration, the obtained initial hot metal data, and components and flow rates of exhaust gases discharged from the converter, A mathematical model that expresses the fire point reaction , which is the oxidation reaction between oxygen supplied from the lance to the hot metal and the above hot metal, and the above hot metal that proceeds in a different area from the fire point area where the above fire point reaction proceeds. to represent slag metal interface reaction is a reaction at the interface between the slag and the mathematical model based on competitive reaction model in which the fire point reaction were considered were combined composite anti The estimation unit sequentially estimates the molten iron Si concentration and the Si equilibrium concentration at the slag metal interface using a model, and the difference between the molten iron Si concentration estimated by the estimation unit and the Si equilibrium concentration is predetermined A hot metal preparatory process control device is provided, which includes a silicon removal processing end determination unit that determines a time point equal to or lower than a threshold value as a completion time of silicon removal processing.

  The above-described hot metal pretreatment method sequentially estimates the hot metal Si concentration using a composite reaction model which is a model obtained by combining a mathematical model expressing a fire point reaction and a mathematical model expressing a slag-metal interface reaction. Thereby, it is possible to estimate with high accuracy the change of the hot metal component which changes due to the fire point reaction and the slag metal interface reaction which are caused by the blowing using the converter.

  As described above, according to the present invention, it is possible to more accurately determine the end point of the desiliconization treatment in the hot metal pretreatment using a converter.

It is a figure showing an example of 1 composition of a system concerning one embodiment of the present invention. It is a figure showing an outline of a compound reaction model concerning the embodiment. It is a figure which shows the flowchart of the hot metal preparatory processing method by the system which concerns on the embodiment. It is a graph which shows the change of the oxygen distribution rate by the fire point reaction of each hot metal component in each Example for every component. It is a graph which shows the change of the presumed density | concentration of Si in the hot metal in each Example. It is a graph which shows the change of the presumed density | concentration of P in the hot metal in each Example, and the measured density | concentration of P in the molten hot metal.

  The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. In the present specification and the drawings, components having substantially the same functional configuration will be assigned the same reference numerals and redundant description will be omitted.

<1. System configuration>
FIG. 1: is a figure which shows one structural example of the hot metal preparatory processing system 1 which concerns on one Embodiment of this invention. Referring to FIG. 1, the hot metal pretreatment system 1 according to the present embodiment includes a hot metal pretreatment system 10, a hot metal pretreatment control apparatus 20, a server 30, and an output unit 40.

(Pot hot metal pretreatment equipment 10)
The hot metal pretreatment facility 10 includes a converter 11, a flue 12, a top blowing lance 13, an exhaust gas component analyzer 101, and an exhaust gas flow meter 102. The hot metal pretreatment facility 10 controls the start and stop of the supply of oxygen to the hot metal by the upper blowing lance 13 based on the control signal output from the hot metal pretreatment controller 20 and the control regarding the discharge by the converter 11. Do. Although not shown, the hot metal pre-treatment facility 10 has an oxygen supply device for supplying oxygen to the upper blowing lance 13 and a drive system for charging a cooling material to the converter 11. Various devices used for blowing by a general converter such as a cold material charging device or a secondary material charging device having a drive system for charging the secondary material to the converter 11 may be provided.

  An upper blowing lance 13 used for blowing is inserted from the furnace port of the converter 11, and the oxygen 14 sent from the acid feeder is supplied to the molten iron in the furnace through the upper blowing lance 13. In addition, an inert gas such as nitrogen gas or argon gas is introduced from the bottom of the converter 11 as the bottom blowing gas 15 for stirring the hot metal. In the furnace of the converter 11, a molten metal discharged from the blast furnace, a small amount of iron scrap, and an auxiliary raw material 16 for forming slag such as quick lime are charged. When the auxiliary material 16 is powder, it may be supplied into the converter 11 together with the oxygen 14 through the upper blowing lance 13.

Si in the molten metal oxidizes with the supplied oxygen to form an oxide. The oxide formed here is stabilized as slag. Further, C in the hot metal oxidizes with the supplied oxygen to produce CO or CO _{2, which} is discharged from the converter 11 to the flue 12 as an exhaust gas. The oxidation reaction by blowing removes the components of the impurities, and the amount of C in the hot metal is controlled to produce a low-carbon, low-impurity steel.

The exhaust gas generated by blowing is guided to a flue 12 provided outside the furnace of the converter 11. The flue 12 is provided with an exhaust gas component analyzer 101 and an exhaust gas flow meter 102. The exhaust gas component analyzer 101 analyzes components contained in the exhaust gas. The exhaust gas component analyzer 101 analyzes, for example, the concentration of CO and CO ₂ contained in the exhaust gas. The exhaust gas flow meter 102 measures the flow rate of the exhaust gas. The exhaust gas component analyzer 101 and the exhaust gas flow meter 102 sequentially analyze and measure the exhaust gas.

  The data relating to the exhaust gas component analyzed by the exhaust gas component analyzer 101 and the data relating to the exhaust gas flow rate measured by the exhaust gas flow meter 102 (hereinafter these data will be referred to as “exhaust gas data”) It is sequentially output as time series data to the Si concentration estimation unit 202 of the processing control device 20. At this time, the output period of the exhaust gas data output from the exhaust gas component analyzer 101 and the exhaust gas flow meter 102 is synchronized with the estimation period T of the concentration of each component by the Si concentration estimation unit 202.

(Pot hot metal pre-treatment control device 20)
The hot metal preparatory process control device 20 includes a hot metal data acquisition unit 201, a Si concentration estimation unit 202, and a silicon removal processing end determination unit 203. The hot metal preparatory process control device 20 includes a hardware configuration such as a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and a communication device. The hot metal data acquisition unit Each function of 201, the Si concentration estimation unit 202, and the silicon removal processing end determination unit 203 is realized. In FIG. 1, among the functions possessed by the hot metal preparatory process control device 20, only the functions characteristic of the present invention are mainly illustrated. The hot metal preparatory process control apparatus 20 may have a general function required when performing control concerning a hot metal preparatory process besides the function to illustrate. For example, the hot metal pretreatment control device 20 may have a function of controlling the charging of the cooling material into the converter 11 or a function of controlling the charging of the auxiliary material into the converter 11. Various other known techniques may be applied to other general functions, and thus detailed description will be omitted here.

The hot metal pretreatment controller 20 estimates the concentration of each component in the hot metal or the slag including the hot metal Si concentration, using the various data stored in the server 30 and the exhaust gas data as input values. Then, the hot metal preparatory process control device 20 determines the end of the silicon removal process based on the comparison result of the estimated Si concentration and the like. When it is determined that the silicon removal processing has been completed, the hot metal pretreatment processing control device 20 outputs a control signal to stop the blowing, start of the intermediate discharge, or the like to the hot metal pretreatment facility 10. For example, the hot metal pretreatment control device 20 once stops blowing at the end of the silicon removal processing, discharges all or part of the slag remaining in the converter 11, and then restarts the control signal, It may be output to the hot metal pretreatment facility 10. Thereby, the SiO ₂ in the converter 11 is discharged, so the basicity of the slag in the converter 11 becomes high. Therefore, the efficiency of the dephosphorization process can be improved. Hereinafter, each function which the hot metal preparatory process control apparatus 20 has is demonstrated.

  The molten metal data acquiring unit 201 acquires the molten metal data 301, the parameters 302, and the target data 303 stored in the server 30, and outputs the acquired various data to the Si concentration estimating unit 202. The molten metal data 301 is various data related to molten metal in the furnace of the converter 11. For example, the molten metal data 301 includes information on molten metal (initial molten metal weight for each charge, concentration of molten metal components (C, Si, Fe, Mn, P, etc.), molten metal temperature, molten metal ratio, etc.). The parameters 302 are various parameters used in the Si concentration estimation unit 202. The parameters 302 include various coefficients and parameters such as a silicon removal rate constant and a mass transfer coefficient. The target data 303 includes data such as a target component and a target temperature for each charge after blowing. Further, the target data 303 includes a threshold value Th used to determine the end of the silicon removal processing. The threshold Th will be described later.

  The Si concentration estimation unit 202 determines the concentration of the molten metal component, the concentration of the slag component, etc. based on the various data acquired by the molten metal data acquisition unit 201 and the exhaust gas data acquired from the exhaust gas component analyzer 101 and the exhaust gas flow meter 102. presume. In addition, a slag component is a component of the oxide contained in slag. For example, the Si concentration estimation unit 202 estimates the molten Si concentration, the Si equilibrium concentration at the slag metal interface, and the like. More specifically, the Si concentration estimation unit 202 solves the molten Si concentration, the Si equilibrium concentration, and the like every estimated period T by solving the equations (3) to (17) constituting the composite reaction model described later in a simultaneous manner. Estimate sequentially.

  The molten metal data 301 is initial molten metal data for each charge. Therefore, the Si concentration estimation unit 202 uses the molten metal data 301 as an input value in the first estimation process, but uses an estimation result one cycle before as an input value in the estimation process after the first time. The estimation result includes, for example, molten iron data such as the concentration of the molten iron component including the Si concentration and the concentration of the slag component, or the temperature in each region, estimated one cycle before by the Si concentration estimation unit 202. Thus, the Si concentration estimation unit 202 can sequentially estimate the molten Si concentration that changes for each estimated period T.

  The estimation period T is synchronized with the output period of the exhaust gas data analyzed and measured by the exhaust gas component analyzer 101 and the exhaust gas flow meter 102 as described above. This makes it possible to estimate the hot metal Si concentration based on the latest exhaust gas data. The Si concentration estimation unit 202 outputs the estimated molten Si concentration and Si equilibrium concentration to the silicon removal processing end determination unit 203. Further, the Si concentration estimation unit 202 may output the estimation result to the output unit 40.

  As described above, the Si concentration estimation unit 202 estimates the molten Si concentration and the like by using the composite reaction model. Details of the complex reaction model will be described later.

  The silicon removal processing end determination unit 203 compares the molten Si concentration estimated by the Si concentration estimation unit 202 with the Si equilibrium concentration at the slag metal interface, and determines whether to end the silicon removal processing based on the comparison result. judge. Specifically, the silicon removal processing end determination unit 203 determines whether or not the difference between the molten Si concentration and the Si equilibrium concentration (hereinafter referred to as “Si concentration difference”) falls below the threshold value Th. If it is determined that the Si concentration difference is lower than the threshold Th, the silicon removal processing end determination unit 203 outputs a control signal related to the end of the silicon removal processing to the hot metal pretreatment apparatus 10. The control according to the end of the desiliconization process is, for example, stop control of the blowing by the upper blowing lance 13 or start control of the intermediate discharge process by the converter 11. On the other hand, when it is determined that the Si concentration difference does not fall below the threshold Th, the Si concentration estimation unit 202 estimates the concentration again.

(Server 30)
The server 30 has a hardware configuration such as a CPU, a ROM, a RAM, and a communication device. The server 30 stores various data used in the hot metal preparatory process control device 20. The server 30 stores, for example, hot metal data 301, parameters 302, target data 303, and the like as shown in FIG. These data may be added, updated, changed or deleted via an input device or communication device (not shown). Various data stored in the server 30 are called by the molten metal data acquisition unit 201. In addition, the server 30 may sequentially store the estimation result of the Si concentration estimation unit 202. Although the server 30 according to this embodiment is configured separately from the hot metal preparatory process control device 20, in another embodiment, the server 30 is integrated with the hot metal preparatory process control device 20. It may be configured.

(Output unit 40)
The output unit 40 is realized by an output device such as a display, a printer, or a communication device. The output unit 40 outputs, for example, the estimation result output from the Si concentration estimation unit 202. In addition, the output unit 40 may output the estimation result sequentially stored in the server 30. Thereby, the estimation result by the Si concentration estimation unit 202 can be analyzed ex post. In addition, at the end of the silicon removal processing, the output unit 40 may perform an output such as a display indicating the end of the silicon removal processing. As a result, an operator or the like who has browsed the information output by the output unit 40 can recognize the end of the silicon removal processing.

<2. Complex reaction model>
The configuration of the hot metal preparatory process system 1 according to the present embodiment has been described above. Next, a composite reaction model used to estimate the molten metal Si concentration and the like in the Si concentration estimation unit 202 according to the present embodiment will be described. The Si concentration estimation unit 202 estimates the concentration of the molten metal component including the Si concentration and the concentration of the slag component by sequentially estimating the simultaneous equations represented by the following formulas (3) to (17).

(Outline of complex reaction model)
The dephosphorization reaction shown by Formula (1) occurs at the slag metal interface. The slag metal interface is an interface between the hot metal and the slag in the converter 11. S. Ohguchi et. Al: 'Simultaneous dephosphorylation and desulphurization of molten pig iron' for a model expressing a reaction at the slag metal interface (hereinafter referred to as “slag metal interface reaction”) (so-called “competitive reaction model”) Ironmaking and Steelmaking, 11, (1984), p. 41 (hereinafter, the document is referred to as "non-patent document"). This competitive reaction model can be applied to the mass transfer of the components contained in hot metal and slag at the slag metal interface. That is, it is possible to estimate the concentration of each component in hot metal and slag by using the above-mentioned competitive reaction model.

However, the conventional competitive reaction model is a model applicable only to the slag metal interface reaction, and the oxidation reaction (so-called "fire point reaction") generated between oxygen supplied by blowing and molten metal is a competing reaction. Not reflected in the model. Therefore, for example, the movement of oxides such as SiO ₂ generated by the fire point reaction to the slag is not reflected in the conventional competitive reaction model. Therefore, it has been difficult to use the conventional competitive reaction model as it is for estimating the concentration of each component in hot metal and slag in hot metal pretreatment involving hot point reaction.

  Therefore, the inventors of the present invention have a mathematical model representing a fire point reaction and a mathematical model representing a slag metal interface reaction based on a competitive reaction model which progresses in a different area from the area where the fire point reaction progresses. We have come to propose a complex reaction model.

FIG. 2 is a diagram showing an outline of a combined reaction model of the fire point reaction and the slag metal interface reaction according to the present embodiment. As shown in FIG. 2, movement of substances contained in the hot metal can occur between the spark point region where the fire point reaction takes place and the slag metal interface. In addition, oxides such as SiO ₂ and FeO generated by the fire point reaction move to the slag. The mass transfer amount of these oxides is calculated based on the exhaust gas data generated by the decarburization reaction. A reaction model that takes into account two points of (a) mass transfer of each component in hot metal between multiple regions and (b) mass transfer of oxide produced by the fire point reaction to slag is a combined reaction model. .

The combined reaction model is a combined model of mass balance and heat balance in the fire point reaction, and mass balance and heat balance in the slag metal interface reaction. The mass balance and heat balance are the balance of mass transfer and heat transfer of each component between the three regions of the fire point region, the slag region, the relevant heat point region and the hot metal region other than the relevant slag region. . In the complex reaction model, mass transfer of an oxide containing SiO ₂ or the like generated by the fire point reaction to the slag metal interface is incorporated into the competitive reaction model. The inventors found that this makes it possible to estimate the concentration of each component in hot metal and slag containing Si with high accuracy. The present inventors have also found that it is possible to estimate with high accuracy the formation rate of oxides such as SiO ₂ generated by the fire point reaction by using exhaust gas data in the fire point reaction. . Hereinafter, a composite reaction model, which is a model in which a mathematical model expressing a fire point reaction and a mathematical model expressing a slag metal interface reaction are combined, will be specifically described.

Incidentally, in the following description, unless otherwise described, [X] is to express the concentration of the element X contained in the hot metal, (XO _n) is representing the concentration of the oxide XO _n of the element X contained in slag Do. (XO _n ) is represented by the reaction formula of the following formula (2), and n is a value determined in accordance with the element X.

また、以下の説明においては、特に説明がない限り、各成分の濃度の単位である［質量％］は、［％］と記載する。

Moreover, in the following description, unless otherwise described, [mass%] which is a unit of concentration of each component is described as [%].

(Fire point reaction)
First, a mathematical model that represents the fire point response will be described. In the fire point region, oxygen is supplied from the upper blowing lance 13 or the like to the hot metal, whereby an oxidation reaction of Si, C and Fe contained in the hot metal occurs. The mass balance by the Si, C and Fe fire point reaction is expressed by the following formulas (3) to (5). Formula (3) shows the mass balance of Si in the fire point area | region by desiliconization reaction. Formula (4) shows the mass balance of C in the fire point area | region by decarburization reaction. Equation (5) shows the mass balance of Fe in the fire point region.

_Here, [Si f], _[C f], and [Fe _f] is a hot metal-containing component [%] in the fire spot region. [Si], [C], and [Fe] are hot metal-containing components [%] other than the fire point region. k _Si is a _silicon removal reaction rate constant [% / s]. ΔC is a decarburization rate [% / s] obtained from exhaust gas data. ΔFe is the oxidation rate of Fe [% / s] obtained from the exhaust gas data. V _f is the hot metal deposit [m ³ ] in the fire point region. Also, Q is the amount of reflux [m ³ / s] of the hot metal in the converter 11.

The decarburization rate ΔC is calculated by using the component and flow rate of the exhaust gas contained in the exhaust gas data. Specifically, as shown in the following formula (6), the decarburization rate ΔC is to use the flow rate or the like of the gas component containing at least one of CO and CO ₂ contained in the exhaust gas discharged from the converter 11. Calculated by

Here, Q _offgas is the flow rate [Nm ³ / hr] of the exhaust gas discharged from the converter 11, and the value measured by the exhaust gas flow meter 102 is used. CO, and CO ₂ in the formula (6) in is the concentration of CO discharged from the converter 11, and CO ₂ concentration [%], analyzed values by the exhaust gas component analyzer 101 is used. W _f is the weight [ton] of hot metal in the fire point region.

Next, a method of calculating the oxidation rate ΔFe of Fe will be described. In the present invention, it is assumed that the oxygen supplied to the hot metal is all used for the oxidation reaction by Si, C and Fe in the hot metal. Generally, it is known that the oxidation reaction of Si and C in hot metal proceeds preferentially as compared with the oxidation reaction with Fe in hot metal. Therefore, the present invention assumed that only residual oxygen which did not react with Si or C in the molten metal reacts with Fe in the molten metal. Based on the above assumption, in the present invention, the oxidation rate ΔFe of Fe is the supply amount of oxygen supplied to the hot metal in the converter 11 (FO ₂ [Nm ³ / hr]) as shown in the following formula (7) From the above, it is determined from the amount of oxygen calculated by subtracting the amount of oxygen consumed by the desiliconization reaction and the decarburization reaction.

  However, when the value in the parenthesis of the first term on the right side of the above equation (7) is less than 0, that is, when the following equation (8) is satisfied, ΔFe = 0 is considered.

  Thus, by using exhaust gas data to calculate the mass balance of Si, C, and Fe in hot metal in the fire point region, it is possible to actually estimate the amount of oxygen that reacts with each hot metal component in the fire point reaction. it can. This makes it possible to more faithfully express the model of the oxidation reaction in the fire point region, and to estimate the concentration of each molten iron component with higher accuracy.

Change in the concentration of Si and Fe is oxidized in the fire spot area _{(d [Si f] / dt} , and _{d [Fe f] / dt [} % / s]) is, SiO ₂ in slag originating from fire point reaction And the change in concentration of FeO. This is because Si and Fe, which are reduced by the oxidation reaction in the fire point region, are converted to SiO ₂ and FeO and are incorporated into the slag. Therefore, the change in concentration of SiO ₂ and FeO in the slag with respect to the weight W _S of the slag due to the fire point reaction is d (SiO _{2 f} ) / dt and d (FeO _f ) / dt [% / s] Then, the above concentration change is expressed by the following equation (9) and equation (10).

  As described above, the mass balance of each component in the fire point region due to the fire point reaction is expressed by Expression (3) to Expression (5), Expression (9), and Expression (10). Moreover, the heat balance in a fire point area | region is represented like following formula (11) in consideration of reaction heat of the oxidation reaction etc. which arise by a fire point reaction.

Here, cp _f is the specific heat [kcal / (kg · ° C.)] of the hot metal in the fire point region. T _f is the temperature [° C.] of the hot metal in the flash point region. H _{REAC, f} is the heat of reaction in the fire spot region [kcal / s], for _example, is calculated by using the _{[Si f], [C f} ], and [Fe _f]. RQ is the amount of heat inflow [kcal / s] to the fire point region due to reflux in the converter, and is calculated using the value of the temperature T of the hot metal in the region other than the fire point region. RQ _f is the heat quantity of discharge [kcal / s] from the fire point region due to reflux in the converter, and is calculated using, for example, the value of T _f .

  From the above, the behavior of the hot metal component in the fire point region and the behavior of the oxide generated by the fire point reaction and flowing into the slag are expressed by the above formulas (3) to (11).

(Slag metal interface reaction)
Subsequently, a mathematical model that represents the slag-metal interface reaction will be described. First, the reaction relating to the molten metal component at the slag metal interface is expressed by mass transfer driven by the difference between the equilibrium concentration of the molten metal component at the slag metal interface and the concentration of the molten metal outside the fire point region. The mass balance of the element X (Si, C, Fe, Mn, P) contained in the hot metal at the slag metal interface is expressed as the following formula (12).

Here, [X] is the concentration [%] of the element X contained in the molten iron in the region other than the fire point region. V is the volume [m ³ ] of hot metal other than the fire point region. A is the interface area [m ² ] of the slag metal interface. K _X is a mass transfer coefficient [m / s] of the element X which is a hot metal component. [X ^* ] is the equilibrium concentration [%] of the element X contained in the molten metal at the slag metal interface. [X _f ] is the concentration [%] of the element X contained in the hot metal in the fire point region. W _{X, SUB} is a term [% / s] for considering an increase in the concentration of the element X which is a molten metal component due to the addition of the auxiliary material.

The above equation (12) corresponds to the mass transfer (Q x ([X _f ]-[X]) of the hot metal component flowing from the fire point region to the region other than the fire point region in addition to the conventional competitive reaction model Express the material balance by). That is, the above equation (12) is not only the mass transfer from the molten metal to the slag metal interface (corresponding to A × K _X × ([X] − [X ^* ])) that proceeds due to the slag metal interface reaction, but also fire Based on the mass transfer from the point area to the area other than the fire point area, the concentration change of the components of Si, C and Fe in the hot metal is calculated. Thereby, the influence of the concentration change of the component of Si, C, and Fe in the hot metal by a fire point reaction can be reflected on slag metal interface reaction.

In the composite reaction model according to the present embodiment, it is assumed that oxides of elements X (e.g., Mn and P) other than Si, C, and Fe are not generated by the fire point reaction. Therefore, regarding the mass balance of the element X, the value of [X _f ]-[X] in the above equation (12) is zero.

Further, as described in the non-patent document, the equilibrium concentration [X ^* ] of the element X contained in the molten metal at the slag metal interface is expressed by using the interface oxygen concentration ao ^* . The interface oxygen concentration ao ^* is calculated by an oxygen balance equation at the slag metal interface.

Next, the reaction for the slag component at the slag metal interface is, like the reaction for the molten metal component, by mass transfer driven by the difference between the equilibrium concentration of the slag component at the slag metal interface and the concentration of the component in the bulk of the slag. Be expressed. The mass balance of the slag component XO _n (SiO ₂ , FeO, MnO, PO _2.5 , AlO _1.5 , CaO, etc.) at the slag metal interface is expressed as the following equation (13).

Here, (XO _n ) is the concentration [%] of the oxide of the element X contained in the slag. V _s is the volume [m ³ ] of the slag. K _XOn is a mass transfer coefficient of the oxide XO _n is slag component [m / s]. (XO _n ^* ) is the equilibrium concentration [%] of the oxide of the element X contained in the slag at the slag metal interface. W _{XOn, SUB} is a term to account for the increase in concentration of the oxide XO _n is slag components from investing the adjuncts quicklime or scale, etc. [% / s].

Further, as shown in FIG. 2, the concentration of SiO ₂ and FeO contained in the slag also changes due to the influx of oxides produced by the fire point reaction into the slag. Therefore, for the concentration change of SiO ₂ and FeO, it is necessary to consider not only the concentration change due to the slag metal interface reaction but also the formation rate of the oxide produced by the fire point reaction. Therefore, the concentration change of SiO ₂ and FeO in the slag is obtained by adding the term of the concentration change in the slag due to the oxide produced by the fire point reaction to the conventional competition reaction model. Calculated using). Thereby, the change of the density | concentration of the slag component by the inflow to the slag of the oxide produced | generated by the fire point reaction can be expressed.

Here, (SiO ₂ ) represents the concentration of SiO ₂ in the slag, and (SiO ₂ ^* ) represents the equilibrium concentration of SiO _{2 at} the slag metal interface.

Here, (FeO) represents the FeO concentration in the slag, and (FeO ^* ) represents the equilibrium concentration of FeO at the slag metal interface.

  As described above, the mass balance of each component at the slag metal interface due to the slag metal interface reaction is expressed by equations (12) to (15). Further, the heat balance of the molten metal portion constituting the slag-metal interface reaction and the heat balance of the slag portion take into account reaction heat such as reaction caused by the slag-metal interface reaction, and the following equations (16) and (17) Each is expressed as

Here, W is the weight [ton] of the hot metal in the region other than the fire point region. cp is the specific heat [kcal / (kg · ° C)] of the hot metal in the region other than the fire point region. T is the temperature [° C.] of the hot metal in the region other than the fire point region. H _reac is the reaction heat [kcal / s] distributed to the molten metal among the reaction heat generated in the slag metal interface reaction, and is calculated based on the mass transfer of each component involved in the slag metal interface reaction. Further, Q _SUB is a heat dissipation amount [kcal / s] generated by the dissolution of the auxiliary material in the hot metal.

Here, cp _S is the specific heat of slag [kcal / (kg · ° C.)]. T _s is the temperature of the slag [° C.]. H _{reac, S} is the reaction heat [kcal / s] distributed to the slag among the reaction heat generated by the slag metal interface reaction, and is calculated based on the mass transfer of each component involved in the slag metal interface reaction. Further, RQ _S is a heat removal amount [kcal / s] from the slag surface.

  From the above, the behavior of the molten metal component and the slag component at the slag metal interface including the behavior of the molten metal component due to the fire point reaction is expressed by the above formulas (12) to (17).

As described above, the complex reaction model is an equation representing a slag metal interface reaction configured by the equations (3) to (11) expressing the fire point reaction and the competitive reaction model considering the fire point reaction 12) It is a mathematical model which compounded equation (17). The Si concentration estimation unit 202 according to the present embodiment solves simultaneously the simultaneous equations consisting of the equations (3) to (17) constituting the complex reaction model, to thereby obtain the concentration of the molten metal component including the Si concentration and the slag component Estimate the concentration of For example, the Si concentration estimation unit 202 can estimate the molten Si concentration [Si] and the Si equilibrium concentration [Si ^* ] at the slag metal interface by using the above-mentioned combined reaction model.

<3. Hot metal pretreatment method>
FIG. 3 is a diagram showing a flowchart of a hot metal pretreatment method by the hot metal pretreatment system 1 according to the present embodiment. The flow of the hot metal pretreatment method by the hot metal pretreatment system 1 according to the present embodiment will be described with reference to FIG. 3.

  First, the molten metal data acquisition unit 201 of the molten metal preliminary processing control device 20 acquires the molten metal data 301, the parameter 302, and the target data 303 stored in the server 30 (S101). Next, the Si concentration estimation unit 202 acquires exhaust gas data from the exhaust gas component analyzer 101 and the exhaust gas flow meter 102 (S103). In addition, when the estimation of the molten Si concentration or the like is performed in step S105 one cycle earlier, the Si concentration estimation unit 202 acquires the estimation result of the concentration of each component one cycle earlier.

  Next, the Si concentration estimation unit 202 estimates the molten Si concentration and the like using the composite reaction model based on the various data acquired in step S101 and step S103 or the estimation result one cycle before (S105).

Subsequently, the silicon removal processing end determination unit 203 determines whether the difference between the molten Si concentration estimated by the Si concentration estimation unit 202 and the Si equilibrium concentration at the slag metal interface, that is, the Si concentration difference falls below the threshold value Th. To do (S107). Here, the Si concentration difference corresponds to [X]-[X ^* ] (that is, [Si]-[Si ^* ]) included in the right side of the above formula (12) or formula (13). The Si concentration decreases as the reaction in the converter 11 by blowing progresses, so the Si concentration difference also gradually decreases. The decrease in the Si concentration difference indicates that the mass transfer of the Si component from the hot metal to the slag is reduced, that is, the desiliconization reaction is slowed down. Strictly speaking, the silicon removal treatment ends when the Si concentration difference gradually decreases to zero, but practically, when the silicon concentration difference becomes a sufficiently small value, the silicon removal treatment is ended. It is regarded. Therefore, the silicon removal processing end determination unit 203 can appropriately determine the end time of the silicon removal processing by setting an appropriate threshold value.

  Here, when the threshold value Th is set high, the time of the silicon removal processing can be shortened. However, since the concentration of Si remaining in the hot metal remains at a high value, the cost of inputting auxiliary materials such as quick lime used in the post-treatment dephosphorization treatment becomes large. On the other hand, when the threshold value Th is set low, the molten Si concentration can be controlled lower. However, continuing the silicon removal treatment even after the silicon removal reaction has slowed leads to an extension of the silicon removal treatment time. This may cause, for example, a decrease in yield due to the increase in (FeO) generated by the fire point reaction. Therefore, it is necessary to set the threshold Th appropriately. For example, in the present embodiment, an appropriate threshold value Th is set to 0.01%.

  If it is determined in step S107 that the Si concentration difference does not fall below the threshold Th (NO), the Si concentration estimation unit 202 estimates the Si concentration or the like again in step S103. In the case where the Si concentration difference does not fall below the threshold value Th, the hot metal preparatory system 1 repeatedly carries out the above-described steps S103 to S107 for each estimated period T.

  On the other hand, if the Si concentration difference is less than the threshold Th in step S107 (YES), the silicon removal processing end determination unit 203 determines that the time when the silicon concentration difference is less than the threshold Th is the silicon removal processing end time, The control signal relating to the end of the process is output to the hot metal pretreatment apparatus 10. For example, the silicon removal processing end determination unit 203 may output a control signal related to the start of the intermediate displacement processing to the hot metal pretreatment apparatus 10 as a control signal related to the completion of the silicon removal processing (S109). In addition, the silicon removal processing end determination unit 203 may output, to the hot metal pretreatment facility 10, a control signal related to the stop of the acid transfer into the converter 11 by the upper blowing lance 13.

  As described above, according to the hot metal pretreatment method according to the present embodiment, by using a mathematical model using a complex reaction model in the desiliconization process using the converter 11, the hot metal Si concentration and the like can be made with high accuracy. It can be estimated. Therefore, based on the said estimation result, determination of the completion | finish time of a silicon removal process can be performed appropriately. Thereby, it is possible to suppress the input cost of secondary raw materials such as quick lime used for the dephosphorization treatment without causing the deterioration of the production efficiency and the hot metal quality due to the desiliconization treatment.

  In the hot metal pretreatment system 1 according to the present embodiment, the blowing process is once stopped at the end of the desiliconation process determined by the hot metal pretreatment process control device 20, and the intermediate discharge of slag remaining in the converter 11 is performed. Although it has been described that control is performed so as to perform acupuncture and then to restart blowing, the present invention is not limited to this example. For example, the hot metal pretreatment system 1 may not perform the intermediate removal after the determined end point of the silicon removal processing. Instead, the hot metal pretreatment system 1 may perform control for promoting the dephosphorization process after the determined point of time when the desiliconization process is completed. This enables more efficient dephosphorization treatment in the hot metal.

  Next, examples of the present invention will be described. The following examples are merely for verifying the effects of the present invention, and the present invention is not limited to the following examples.

  In this embodiment, the estimation accuracy of the Si concentration according to the present invention was verified. Specifically, first, the oxygen distribution rate estimated based on the exhaust gas data was evaluated. The oxygen distribution rate will be described later. Next, it evaluated about the change (desiliconization rate) of the presumed density | concentration of hot metal Si estimated by the hot metal pre-processing method which concerns on this embodiment. Furthermore, the hot metal P concentration estimated by the hot metal pre-treatment method according to the present embodiment was compared with the P concentration measured after blowing, and the estimation accuracy of the hot metal Si concentration was evaluated. The reason why comparison is performed using not the molten Si concentration but the actual value of the molten P concentration is that it is technically difficult to directly evaluate the Si concentration at the end of the silicon removal treatment. Instead, the estimation accuracy of the hot metal Si concentration was evaluated by comparing the actual measurement value of the hot metal P concentration with the P concentration estimated by the hot metal pretreatment method according to the present embodiment.

(Test conditions)
Initial molten metal data including the concentration [%] of initial molten metal component, molten metal temperature [° C], and basic unit [kg / ton] to molten metal weight of secondary materials (quick lime and scale), and actual molten metal pretreatment time [Sec] is shown in Table 1 below for each example.

  The molten metal data in each Example shown in the above-mentioned Table 1 is molten metal data for every charge charged into the converter 11. During the hot metal pretreatment in each example, the hot metal Si concentration and the hot metal P concentration were estimated using the hot metal pretreatment method according to the present embodiment. The oxygen distribution rate was also estimated during the hot metal pretreatment. Then, the estimated P concentration at the time when the actual blowing time elapsed, and the actually measured value of the hot metal P concentration subjected to the hot metal pretreatment were compared.

(Test results)
First, it evaluated about the oxygen distribution rate by the fire point reaction of Si in a hot metal. FIG. 4 is a graph showing, for each component, a change in oxygen distribution rate due to a fire point reaction of each molten metal component in each example. FIG. 4A is a graph corresponding to Example 1, and FIG. 4B is a graph corresponding to Example 2. The oxygen distribution ratio means the reaction ratio of oxygen supplied from the top blowing lance 13 to Si, C, or Fe in hot metal. The oxygen distribution rate is calculated using the equations (3) to (8).

  According to the graph shown in FIG. 4A, it can be seen that the oxygen distribution ratio to Si in the hot metal in Example 1 changes between approximately 60% and 80%. On the other hand, according to the graph shown in FIG. 4 (b), it can be seen that the oxygen distribution ratio to Si in hot metal in Example 2 changes between approximately 40% and 60%. From the above results, it has been found that the oxygen distribution rate can fluctuate without necessarily taking a constant value for each charge of the molten metal of the converter 11.

  Next, the silicon removal rate of Si in hot metal was evaluated. FIG. 5 is a graph showing a change in estimated concentration of Si in hot metal in each example. FIG. 5A is a graph corresponding to Example 1, and FIG. 5B is a graph corresponding to Example 2. It was found that the slope of the graph shown in FIG. 5 (a) was larger than the slope of the graph shown in FIG. 5 (b). That is, it was found that the silicon removal rate of Example 1 was larger than the silicon removal rate of Example 2 with respect to the silicon removal rate. As shown in FIG. 4, it is considered that the reason is that the oxygen distribution rate of Si in Example 1 is larger than the oxygen distribution rate of Si in Example 2.

  Next, the estimated concentration of P in the molten metal was compared with the measured concentration of P in the molten metal subjected to actual hot metal pretreatment. FIG. 6 is a graph showing the change in the estimated concentration of P in hot metal and the measured concentration of P in blown metal in each example. FIG. 6A is a graph corresponding to Example 1, and FIG. 6B is a graph corresponding to Example 2. In addition, the measurement density | concentration of P is the value measured immediately after the completion of blowing in each Example.

  Referring to FIGS. 6 (a) and 6 (b), in each of Example 1 and Example 2, the estimated concentration and the measured concentration of P at the end of the blow were nearly identical. This indicates that the estimation accuracy of the hot metal P concentration estimated by the hot metal pretreatment method according to the present embodiment is high.

  In addition, although the initial concentration of P in hot metal in each example was the same concentration (0.096%), the estimated concentration of P in hot metal of Example 1 at the end of hot metal pretreatment was It showed a lower value than the estimated concentration of P in the hot metal of Example 2. This is considered to be because the silicon removal rate of Example 1 is larger than the silicon removal rate of Example 2 with respect to the silicon removal rate estimated by the hot metal pretreatment method according to the present embodiment, as shown in FIG. .

  On the other hand, the measured concentration of P in the hot metal of Example 1 at the end of the hot metal pretreatment also showed a lower value than the measured concentration of P in the hot metal of Example 2. This confirms that the silicon removal rate of Example 1 is larger than the silicon removal rate of Example 2 with respect to the silicon removal rate in actual hot metal pretreatment. That is, it was shown that the estimation accuracy of the desiliconization rate by the hot metal pretreatment method according to the present embodiment is high. Since the estimation speed of the desiliconization rate by the hot metal pretreatment method according to the present embodiment is high, it can be said that the estimated concentration of the hot metal Si concentration is also high.

  As described above, according to the example of the hot metal pretreatment method according to the present embodiment, it was found that the hot metal Si concentration can be estimated with high accuracy. Therefore, according to the present invention, it is possible to determine with high accuracy the end point of the silicon removal treatment by estimating the hot metal Si concentration with high accuracy.

  Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is obvious that those skilled in the art to which the present invention belongs can conceive of various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also fall within the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 hot metal pre-treatment system 10 hot metal pre-processing installation 11 converter 12 flue 13 top blow lance 20 hot metal pre-treatment control device 30 server 40 output part 101 exhaust gas component analyzer 102 exhaust gas flow meter 201 hot metal data acquisition part 202 Si concentration estimation part 203 Silicon removal processing end judgment unit

Claims (6)

A method of hot metal pre-treatment by blowing using a converter,
A molten metal data acquisition step of acquiring initial molten metal data including an initial concentration of molten metal components including at least Si, Fe, and C;
In the oxidation reaction between the oxygen supplied from the top lance to the molten metal and the molten metal, based on the acquired initial molten metal data and time-series exhaust gas data including the components and flow rates of the exhaust gas discharged from the converter In order to express a slag metal interface reaction which is a reaction at the interface between the hot metal and the slag which progresses in a region different from a mathematical model expressing a certain fire point reaction and a fire point region which is a region in which the fire point reaction proceeds. Then, using a complex reaction model in which the above-mentioned fire point reaction is considered and a mathematical model based on the competition reaction model are combined, the hot metal Si concentration and the Si equilibrium concentration at the slag metal interface are sequentially estimated. Estimation step,
Desiliconation processing end determination step in which the time point at which the difference between the estimated molten iron Si concentration and the Si equilibrium concentration is equal to or less than a predetermined threshold is determined as the end time of the desiliconization processing;
Hot metal pretreatment method including.   The hot metal pre-treatment method according to claim 1, wherein the predetermined threshold is 0.01%.   When it is determined that the desiliconization processing is completed, the blowing is stopped, a part or all of the slag generated in the converter is discharged, and then the blowing is resumed. The hot metal pre-treatment method according to claim 1 or 2.   In the composite reaction model, the concentration change of the molten metal component is caused by the mass transfer of the molten metal component from the molten metal to the slag metal interface, and the molten metal component from the fire point region to a region different from the fire point region. The hot metal pretreatment method according to any one of claims 1 to 3, which is calculated based on the mass transfer of   In the composite reaction model, the concentration change of the slag component is generated by the mass transfer of the slag component from the slag to the slag metal interface proceeding by the slag metal interface reaction, and the oxidation reaction in the fire point region. The hot metal pretreatment method according to claim 4, which is calculated based on mass transfer of the slag component contained in the oxide. A hot metal pretreatment control device for controlling hot metal pretreatment by blowing using a converter, comprising:
A molten metal data acquisition unit that acquires initial molten metal data including initial concentrations of molten metal components including at least Si, Fe, and C;
In the oxidation reaction between the oxygen supplied from the top lance to the molten metal and the molten metal, based on the acquired initial molten metal data and time-series exhaust gas data including the components and flow rates of the exhaust gas discharged from the converter In order to express a slag metal interface reaction which is a reaction at the interface between the hot metal and the slag which progresses in a region different from a mathematical model expressing a certain fire point reaction and a fire point region which is a region in which the fire point reaction proceeds. Then, using a complex reaction model in which the above-mentioned fire point reaction is considered and a mathematical model based on the competition reaction model are combined, the hot metal Si concentration and the Si equilibrium concentration at the slag metal interface are sequentially estimated. An estimation unit,
A silicon removal end determination unit that determines a point at which a difference between the molten iron Si concentration estimated by the estimation unit and the Si equilibrium concentration is equal to or less than a predetermined threshold as an end time of the silicon removal processing,
, A hot metal pretreatment control device.

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