JP6841391B2 - Estimating method and estimation device for the amount of residual slag in the furnace - Google Patents

Description

The present invention is a method for estimating the amount of residual slag in a furnace, that is, slag is discharged from the furnace mouth while leaving molten iron in the converter by tilting the converter after desiliconization or dephosphorization treatment in the converter. The present invention relates to a method of estimating the amount of slag remaining in the furnace after slag.

By tilting the converter after desiliconization or dephosphorization of hot metal in the converter, a part of the slag is allowed to flow down from the furnace mouth into the drain pot arranged below while leaving the molten iron in the converter. There is a method in which the converter is slagged and then the converter is made upright again to add auxiliary raw materials such as quicklime (main component is CaO) and then refined (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2007-308773 Japanese Unexamined Patent Publication No. 5-140627 International Publication No. 2018/020929

In this method, the slag is formed (foamed) in the converter to increase the bulk volume of the slag, which facilitates slag removal and secures the amount of slag. Here, in the forming of slag, carbon monoxide (CO) gas is generated by the reaction of carbon (C) in molten iron and iron oxide (FeO) in slag, and the CO gas is held in the slag. appear.

After the slag, the converter is upright and auxiliary materials such as quicklime are added to continue refining. Normally, the amount of auxiliary materials added is adjusted according to the amount of residual slag in the furnace. Therefore, if the estimation of the amount of residual slag in the furnace varies, the amount of auxiliary raw material added will be excessive or insufficient. For example, if the amount of residual slag in the furnace is estimated to be larger than the actual amount, the cost will be deteriorated due to the excessive addition of auxiliary materials. On the other hand, if the amount of residual slag in the furnace is estimated to be smaller than the actual amount, incompatibility of components such as phosphorus due to insufficient addition of auxiliary raw materials (hereinafter referred to as “component loss”) is likely to occur. Usually, in order to prevent the components from coming off, auxiliary raw materials are often added in excess. That is, if the estimation accuracy of the amount of residual slag in the furnace is low, there are problems of cost deterioration due to an increase in the amount of auxiliary raw materials used, an increase in the amount of generated slag, an increase in heat loss, a deterioration in iron yield, and the like.

Conventionally, the amount of residual slag in the furnace is estimated by the operator visually observing the slag state or weighing the slag amount with a weighing device installed on the slag trolley. It has been done by subtracting the amount of slag from the estimated amount of slag inside. However, since the slag formed during the slag calms down and the volume of the slag changes from moment to moment, there is a problem that the estimation accuracy is low in the visual estimation by the operator. Also, in the case of weighing with a weighing device, the formed slag overflows beyond the capacity of the drain pan and damages the weighing device, or the accuracy of the weighing device deteriorates due to vibration of the trolley, etc. It was difficult to perform stable and highly accurate weighing because the equipment maintenance load was high and it was necessary to correct the grain iron content that was inevitably mixed in the slag.

Further, Patent Document 1 finds that there is a correlation between the tilt angle of the converter and the amount of residual slag in the furnace, and discloses a method of controlling the amount of residual slag in the furnace based on the tilt angle. However, this method utilizes the relationship between the tilt angle of the converter and the residual volume in the furnace, and is premised on application to unformed slag after decarburization treatment, that is, slag having a constant bulk density. Therefore, it cannot be applied to formed slag after desiliconization or dephosphorization treatment.
Further, Patent Document 3 discloses a waste weight estimation method for estimating the weight of slag with forming discharged from a converter. In this method, the volume flow transition that estimates the change in volume flow rate of the slag discharged from the converter over time is derived, and the change in bulk density that estimates the change in bulk density of the slag discharged from the converter over time is calculated. The value obtained by deriving and integrating the product of the volume flow rate and the bulk density of the slag at each corresponding time point of the volume flow rate transition and the bulk density transition is estimated as the waste weight of the slag discharged from the converter. Derived as a value.

In view of the problems of the prior art, the present invention relates to an operation in which slag is discharged from the furnace mouth while leaving molten iron in the converter by tilting the converter after desiliconization or dephosphorization treatment in the converter. An object of the present invention is to provide a simple and highly accurate method for estimating the amount of residual slag in a furnace.

In order to estimate the amount of residual slag in the furnace with high accuracy, the inventors of the present application estimated the behavior of the formed slag during slag calming down and changing the bulk volume of the slag, and based on this, estimated the behavior in the furnace. The idea was to estimate the amount of residual slag, and we conducted a diligent study. As a result, a method for estimating the forming sedative characteristics and estimating the amount of residual slag in the furnace based on the estimated forming sedative characteristics and the tilt pattern of the converter during the discharge was established, and the present invention was completed. The gist of the present invention is as follows.

<1>
In the operation of discharging slag from the furnace mouth while leaving molten iron in the converter by tilting the converter after desiliconization or dephosphorization in the converter, the amount of slag remaining in the furnace after the discharge is reduced. It ’s a method of estimation,
Step A in which the slag height in the converter is measured multiple times or continuously after the desiliconization or dephosphorization treatment and before the start of slag removal.
Step B, which estimates the forming sedative characteristics of the slag in the furnace based on the results measured in step A, and step B,
Step C, which estimates the amount of residual slag in the furnace based on the sedation characteristics estimated in step B and the tilt pattern of the converter,
A method for estimating the amount of residual slag in a furnace, which comprises.
<2>
Process C is
Based on the sedation characteristics estimated in step B and the tilt pattern of the converter, the sedation behavior and the discharge behavior are sequentially calculated for each time interval from the start time of slag to the end of slag. The method for estimating the amount of residual slag in the furnace according to <1>, which comprises.
<3>
Process C is
The method for estimating the amount of residual slag in a furnace according to <2>, which includes step E in which the slag state at the start of slag is estimated based on the sedation characteristics estimated in step B.
<4>
Process C is
Step F for estimating the residual slag volume transition based on the tilt pattern of the converter, and
It is characterized by including a sedative characteristic estimated in step B and a step G in which the sedative behavior and the discharge behavior that simultaneously proceed during slag are estimated based on the residual slag volume transition estimated in step F. 1> The method for estimating the amount of residual slag in the furnace.
<5>
Process G is
Based on the sedation characteristics estimated in step B and the residual slag volume transition estimated in step F, the step of sequentially calculating the slag state for each time interval from the start time of slag discharge to the end time of slag discharge. The method for estimating the amount of residual slag in a furnace according to <4>, which comprises H.
<6>
Process G is
The method for estimating the amount of residual slag in a furnace according to <5>, which includes step I in which the slag state at the start of slag is estimated based on the sedation characteristics estimated in step B.
<7>
The method for estimating the amount of residual slag in the furnace according to any one of <4> to <6>, wherein in step F, the volume corresponding to the head portion of the slag flowing out is estimated.
<8>
The method for estimating the amount of residual slag in a furnace according to any one of <1> to <7>, wherein the step A is performed using a microwave range finder.
<9>
In the operation of discharging slag from the furnace mouth while leaving molten iron in the converter by tilting the converter after desiliconization or dephosphorization in the converter, the amount of slag remaining in the furnace after the discharge is reduced. It is a device to estimate
A sedation characteristic estimation unit that estimates the forming sedation characteristics of the slag in the furnace based on the results of measuring the slag height in the converter multiple times or continuously after the desiliconization or dephosphorization treatment and before the start of scavenging.
The amount of residual slag in the furnace is characterized by comprising an in-core residual slag amount estimating unit that estimates the amount of residual slag in the furnace based on the sedation characteristics estimated by the sedation characteristic estimation unit and the tilt pattern of the converter. Estimator.
<10>
The residual slag amount estimation unit in the furnace is
A residual volume transition estimation unit that estimates the residual slag volume transition based on the tilt pattern of the converter,
A slag state estimation unit at the start of slag that estimates the slag state at the start of slag based on the sedative characteristics estimated by the sedation characteristic estimation unit, and a slag state estimation unit at the start of slag.
Based on the sedation characteristics estimated by the sedation characteristic estimation unit and the residual slag volume transition estimated by the residual volume transition estimation unit, the period from the start time of slag to the end of slag is divided by a minute time. The device for estimating the amount of residual slag in a furnace according to <9>, comprising a sequential calculation unit for sequentially calculating the slag state.

According to the present invention, in the operation of discharging slag from the furnace mouth while leaving molten iron in the converter by tilting the converter after the desiliconization or dephosphorization treatment in the converter, the residue in the furnace after the discharge is performed. Estimating the amount of slag becomes easier and the estimation accuracy improves. As a result, variations in the estimation of the amount of residual slag in the furnace can be suppressed, and auxiliary raw materials can be added in just proportion. With the above effects, it is possible to reduce costs (reduce the amount of auxiliary raw materials used, reduce the amount of slag generated, suppress heat loss, and improve iron yield).

It is a figure which shows the time-dependent change of the slag height in the furnace in the state where the converter is upright, (a) shows the state immediately after the desiliconization or dephosphorization treatment is completed, and (b) is desiliconization or desiliconization. It shows the state when a certain amount of time has passed after the completion of phosphorus treatment. It is a figure which shows an example of the result of having measured the slag height in a converter after dephosphorizing treatment. In the example, it is a figure which shows the result of having measured the slag height with a microwave range finder before scavenging, and estimating the forming sedative characteristic from the height change. It is a figure which shows the tilting pattern of the converter in the slag in the Example. In the Example, it is a figure which shows the time-dependent change of the amount of residual slag in a furnace estimated from the forming sedative characteristic shown in FIG. 3A and the tilt pattern shown in FIG. 3B. It is a figure which compared the calculated value from the actual scale value, the estimated value by the method of this invention, the estimated value by the operator's visual inspection, and the estimated value by the method of Patent Document 1 in the estimation of the residual slag amount in the furnace of an Example. .. It is a functional block diagram which shows the structure of the residual slag amount estimation apparatus in a furnace of embodiment. It is a block diagram which shows the structure of the computer which realizes the furnace residual slag amount estimation apparatus of embodiment.

[About forming sedation]
FIG. 1 shows the time course of the slag height in the converter in the state where the converter 6 is upright after the desiliconization or dephosphorization treatment. The upper layer of the slag is a low-density slag layer 3 that is formed and contains a large amount of bubbles, and the lower layer of the slag is a high-density slag layer 4 in which slag that does not contain bubbles after bubble rupture is settled, and the molten iron 5 is below the slag layer 4. FIG. 1A shows a state immediately after the completion of the desiliconization or dephosphorization treatment, and FIG. 1B shows a state when a certain amount of time has passed after the completion of the desiliconization or dephosphorization treatment.

As shown in FIG. 1, it can be seen that with the passage of time, the bubbles in the forming slag (low density slag layer 3) burst and the slag height decreases, that is, the forming calms down. Specifically, since the calmed low-density slag layer 3 becomes the high-density slag layer 4, the height of the low-density slag layer is greatly reduced and the height of the high-density slag layer is slightly increased.

FIG. 2 shows an example of the result of measuring the slag height in the converter after the dephosphorization treatment.
The broken line in the figure shows the continuous measurement result by the microwave range finder 1, and the point (◯) shows the discontinuous measurement result by the measuring rod 2. Both values are almost the same.
The height of the slag in the converter is the height obtained by subtracting the height of the molten iron from the height of the upper surface of the slag, that is, the height of only the slag layer. The height of the upper surface of the slag is measured by the microwave range finder 1 or the measuring rod 2, and the height of the molten iron is subtracted from the height of the upper surface of the slag to calculate the slag height. The molten iron height is calculated from the shape of the converter and the amount of iron charged, or measured before processing.
The measurement with the microwave range finder 1 and the measuring rod 2 can be performed during the dephosphorization treatment or immediately after the dephosphorization treatment, and the time t = 0 means immediately after the completion of the dephosphorization treatment.

[Forming sedation during slag and its effects]
Similarly, forming sedation occurs when the converter is tilted and the slag is discharged by utilizing the increase in the bulk volume of the slag due to forming (while the slag is being discharged).
Therefore, when the forming sedation is fast, the bulk volume of the slag decreases in the latter half of the slag, so that the slag cannot be sufficiently slagged and the amount of residual slag (weight) in the furnace increases. On the other hand, when the forming sedation is slow, the bulk volume of the slag can be secured even in the latter half of the slag, so that the slag can be sufficiently discharged and the amount of residual slag in the furnace is reduced. In this way, the amount of residual slag in the furnace is affected by the forming sedation rate.
In another explanation, even if the same bulk volume of slag remains at the end of scavenging, the ratio of low-density slag and high-density slag to the bulk volume is affected by the forming sedation rate. Even with the same bulk volume, the weight changes according to the ratio of low-density slag and high-density slag, so the amount of residual slag (weight) in the furnace is affected by the forming stagnation rate.

[Forming sedative properties are affected by various factors such as slag physical properties and gas generation rate. ]
Here, the forming situation changes with the passage of time after the desiliconization or dephosphorization treatment, but its sedative properties are affected by the physical properties of the slag (viscosity, surface tension, etc.), the gas generation rate, and the like. Of these factors, the physical properties of slag are affected by the composition and temperature of the slag, and the gas generation rate is affected by the shape of the converter and operating conditions (bottom blowing conditions, etc.) in addition to the composition and temperature of the slag. ..

These compositions, temperatures, and operating conditions are not always constant and vary. Depending on these variations, the forming situation and the amount (weight) of residual slag in the furnace after slag will also vary. Such circumstances make it difficult to accurately estimate the amount of residual slag in the furnace.

Therefore, the inventors of the present application have found that estimating the forming stagnation characteristic is important for estimating the amount of residual slag in the furnace, and establish a method for estimating the forming slag characteristic of the slag in the furnace, and further estimate it. The idea was to estimate the amount of residual slag in the furnace from the forming sedation characteristics and the tilt pattern of the converter during scavenging, and we conducted a diligent study.

[Estimation of sedative characteristics]
Therefore, in the present invention, the slag height in the converter is measured a plurality of times or continuously in a state where the converter is upright after the desiliconization or dephosphorization treatment and before the start of slag removal. Then, the forming sedative characteristics of the slag in the furnace (hereinafter, simply referred to as "sedative characteristics") are estimated from the measurement results.
According to this method, as the measurement result of the slag height used for estimating the sedation characteristics, the result of measuring the slag of the operation for which the amount of residual slag in the furnace is estimated is used. It is possible to capture the influence of the circumstances peculiar to (the operation that is the target of estimation) on the slag. This point is one of the differences from the method disclosed in Patent Document 3.

[Measurement method of slag height change]
The method for measuring the slag height in the converter a plurality of times or continuously is not particularly limited, and for example, there are the following methods.
One method is to immerse the measuring rod 2 a plurality of times and obtain the height of the slag attached to the measuring rod 2 as shown in FIG. Another method is a method of continuously measuring using a microwave range finder 1. A microwave range finder is a device that transmits and receives microwaves having a wavelength that transmits dust in a converter and the like from an antenna installed on the furnace and measures the distance to the upper surface of the slag.

When estimating the sedation characteristics from the measurement results (change in slag height), the method of continuous measurement using a microwave rangefinder or the like is better than the method of non-continuous measurement using a measuring rod or the like. It is advantageous in terms of accuracy, measurement time, and measurement load.

[Specific example of sedative characteristic estimation method]
The specific method for estimating the sedative characteristics from the measurement results is not particularly limited, and for example, there are the following methods.
One method is to estimate by the extrapolation method (extrapolation method) from the measurement results before the start of slag. As another method, there is a method in which a calculation model for estimating the sedation characteristics from the measurement result before the start of slag is created in advance, and the parameters of this calculation model are calculated and estimated from the measurement result before the start of slag. .. Since the forming sedation speed during slag is affected by the shape of the converter and the operating conditions such as the flow rate of bottom blowing gas, it is necessary to conduct a preliminary test for each converter and make the above estimation. Become.

The solid line in FIG. 3A is an estimation result (example described later) by a calculation model for estimating the sedation characteristic. It was estimated by determining the model parameters based on the measurement results before slag (broken line in the figure).

[Estimate the amount of residual slag in the furnace based on the sedative characteristics and tilt pattern]
Next, the amount of residual slag in the furnace is estimated based on the estimated sedative characteristics and the tilt pattern of the converter. A specific example will be described below.

[Derivation of residual slag volume transition _{Vr, t]}
First, the transition V _{r, t} (transition of residual slag volume) in the furnace residual slag volume is estimated based on the tilt pattern.

The volume of residual slag in the furnace during slag varies depending on the tilt pattern of the converter.
For example, if the tilting speed of the converter is very slow and it can be considered that it is tilted almost quasi-statically, the residual slag volume in the furnace at a tilting angle includes the lower end position of the furnace mouth at that tilting angle. It is the volume of the furnace below the horizontal plane minus the volume of molten iron.
On the other hand, when the tilting speed of the converter is relatively high, a volume corresponding to the head portion of the slag flowing out is added as the residual slag volume in the furnace.

Therefore, when estimating the residual slag volume transition in the furnace (residual slag volume transition), it is preferable to consider the head portion from the viewpoint of accuracy. The method for estimating the residual slag volume in the furnace in consideration of the head portion is not particularly limited, and for example, there are the following methods.

One method is to use computational fluid dynamics. In this method, the residual slag volume in the furnace is calculated with the shape and tilt pattern of the converter as input conditions, and the tilt pattern and the residual slag volume in the furnace are associated with each other. In the actual slag, the tilting speed is at most about 1 ° / sec, and if the tilting pattern and the residual slag volume in the furnace are calculated in advance and a regression equation is created, the calculation load can be suppressed. ..
As another method, the same association can be performed by performing a model experiment instead of the computational fluid dynamics calculation.
Since the volume of residual slag in the furnace is affected by the shape of the converter, it is necessary to perform calculations and experiments for each converter and make the above association.

[Estimate the amount of residual slag in the furnace based on the sedative characteristics and residual slag volume]
Next, the amount of residual slag in the furnace is estimated based on the estimated sedative characteristics and the estimated residual slag volume transition.

The time immediately after the desiliconization or dephosphorization treatment is t = 0, the time when the slag starts to flow out from the furnace port is t = t _1, and the time when the slag ends is t = t ₂ .
W _{s and t} are the weights of all the slag in the furnace at time t, V _{f and t} are the volumes of the low-density slag layer _{in the furnace at time t, and V d and t} are the volumes of the high-density slag layer in the furnace at time t. The volumes V _{s and t are the volumes ρ f} of all the slags in the furnace at time t, and _{the bulk density ρ d} of the low density slag layer is the bulk density of the high density slag layer. _{The bulk density ρ f} of the low-density slag layer and the bulk density ρ _d of the high-density slag layer are set to constant values.

(T = 0)
_{In this case, the volumes V f, 0} of the low-density slag layer and the volumes V _{d, 0} of the high-density slag layer immediately after the treatment (t = 0) are obtained by using the equations (1) and (2). Can be done.


... (1)


... (2)

The left side of the equation (1) is the amount of slag in the furnace W _{s, 0} immediately after the treatment (before the slag), and can be obtained by the mass balance calculation.
The left side of the equation (2) is the slag volume V _s, 0 in the furnace at t = 0, and the result measured by a microwave range finder, a measuring rod, or the like can be used.

(T = t ₁ )
Next, the slag state at the start of slag discharge (t = t _{1) is obtained.}

No slag is discharged from the converter from immediately after the treatment to the start of slag. Therefore, it is not necessary to consider the slag emission amount (emission volume) when estimating the slag state. Therefore, it can be obtained by using the following equations (3) to (5).

... (3)

... (4)

... (5)

_{The volumes V f and t 1} of the low-density slag layer at the start of slag discharge (t = t 1) can be obtained by Eq. (3) from the estimated sedative characteristics. _{The function f (V f} , t, ...) On the right side of equation (3) is a function _{of the initial value V f, 0} of the volume of the low-density slag, the elapsed time t, and other parameters. It is considered that the change in the volume of the low-density slag is affected by the initial value and the elapsed time of the volume of the low-density slag.
On the other hand, since the calmed low-density slag layer becomes a high-density slag layer, the volumes V _{d and t1} of the high-density slag layer at the start of scavenging are expressed by Eq. (4) from the mass balance calculation.
The in-furnace slag volumes Vs _{and t1} at the start of slag are expressed by Eq. (5).

(T1 <t <t2)
Next, consider the change in the slag state from the start of slag to the end of slag. From the start of slag to the end of slag, sedation of low-density slag and slag discharge due to tilting proceed at the same time. Therefore, the sedative behavior affects the discharge behavior, and the sedative behavior affects the sedative behavior.
Therefore, in this specific example, the slag state (specifically, the low-density slag layer) is estimated by estimating the sedation behavior and the discharge behavior at each time interval in which the time from the start of the discharge to the end of the discharge is divided by a minute time. Volume, volume of high-density slag layer, etc.) are calculated sequentially.

When t ₁ <t <t ₂ , the relationship between the slag state at a certain current time t and the slag state at the next time point t + Δt is expressed by the following equation.

... (6)

... (7)

... (8)

The two items on the right side of Eq. (6) represent the sedation behavior of the low-density slag layer (specifically, the amount of change in volume of the low-density slag layer due to sedation).
The sedative behavior of the low-density slag layer at the present time t is affected by _{the volumes V f, t of the low-density slag layer at the present time t. Therefore, the volumes V f and t} of the low-density slag layer at the present time are substituted into the two-item function f on the right side of the equation (6).
For example, unlike sedation in which the converter is kept upright, the slag is progressing by the present time t when the slag is _{being discharged (t 1} <t <t _{2). Therefore, the volumes V f and} t of the low-density slag layer at the present time t are small. Therefore, the sedation rate (volume reduction amount) at the present time t is usually smaller than the sedation rate at the present time t when the converter is sedated while it is upright.

_{The three items min (V r, t + Δt} −V _{s, t} , 0) in Eq. (6) represent the discharge behavior (specifically, the amount of change in the volume of the low-density slag layer due to discharge).
V _{r, t + Δt} represent the residual slag volume in the furnace (residual slag volume) at the next time point t + Δt, and of the in-core _{slag volumes V s and t at the present time t, the residual slag in the furnace at the next time point t + Δt.} It is said that the volume exceeding the volume (residual volume) V _{r, t + Δt} is discharged from the slag on the upper layer side to the outside of the furnace. In this example, for the sake of simplicity, only the upper low-density slag layer is discharged.

On the other hand, the volume of the high-density slag layer is expressed by Eq. (7) because the sedative content of the low-density slag increases.

By this sequentially calculated from Haikasu start time (t ₁₎ until Haikasu end (t _2), low density slag layer and the dense layer of slag remaining in the furnace at Haikasu end (t ₂₎ The amount (weight) is calculated, and the total amount is used as the estimated value of the residual slag amount (weight) in the furnace.

[Supplemental Information]
_{In the above specific example, after estimating the residual slag volume transition Vr, t} based on the tilt pattern (tilt angle transition), the discharge behavior (discharge volume) is based on the estimated residual slag volume and sedative characteristics. An example of estimating the _{velocity, min (V r, t + Δt} −V _{s, t} , 0), which is the three items of Eq. (6), has been described. However, it is not always necessary to estimate the residual slag volume transition.
That is, based on the tilt pattern and the sedation characteristic, the discharge behavior (volume change due to discharge, specifically, the part corresponding to the three items of Eq. (6)) is estimated without estimating the residual slag volume transition. You may.

Further, in the above specific example, the calculation that only the low-density slag layer is discharged is used, but the present invention is not limited to this. For example, in consideration of the fact that the high-density slag layer is discharged just before the end of the discharge, the correction may be made accordingly.

Further, in the above-mentioned method, the slag state in the furnace is sequentially calculated for each time interval during the slag (from the start of the slag to the end of the slag) divided by a minute time. Therefore, it can also be used as a control method for controlling the amount of residual slag in the furnace by controlling the tilt pattern of the converter so that the amount of residual slag in the furnace becomes a desired amount.
Further, in the above description, a method of measuring the slag height in the converter in an upright state of the converter has been described, but the present invention is not limited to this. It is preferable to perform the measurement in the upright state of the converter because of the ease of measurement, but it is not always necessary that the converter is in the upright state.

[Estimator]
Next, the furnace residual slag amount estimation device 10 will be described.

The in-core residual slag amount estimation device 10 is an apparatus for estimating the in-core residual slag amount by using the waste weight estimation method according to the above-described embodiment. FIG. 5 shows a functional block diagram showing the configuration of the in-core residual slag amount estimation device 10.

That is, the furnace residual slag amount estimation device 10 includes a sedation characteristic estimation unit 11 and a furnace residual slag amount estimation unit 12.
The sedative characteristic estimation unit 11 estimates the sedative characteristic (for example, the above-mentioned function f) from the measurement result (slag height change) before the start of slag.
The furnace residual slag amount estimation unit 12 derives an estimated value of the furnace residual slag amount based on the sedation characteristic estimated by the sedation characteristic estimation unit 11 and the tilt pattern (tilt angle transition).

Specifically, the furnace residual slag amount estimation unit 12 includes a residual volume transition estimation unit 13, a slag state estimation unit 14 at the start of slag discharge, and a sequential calculation unit 15.
The residual volume transition estimation unit 13 derives the transition of the residual volume of the slag in the furnace (transition of the residual volume) from the tilt pattern.
The slag state estimation unit 14 at the start of slag derives the slag state at the start of slag (for example, the volume of low-density slag or the volume of high-density slag) based on the slag characteristics estimated by the stagnation characteristic estimation unit 11. To do.
The sequential calculation unit 15 determines the sedation behavior (for example, the volume change of the low-density slag due to sedation) and the discharge behavior (for example, the low-density slag due to the discharge) for each time step in which the period from the start of the discharge to the end of the discharge is divided by a minute time. Volume change) is calculated sequentially.

The furnace residual slag amount estimation device 10 can be realized by, for example, the computer 20 shown in FIG. The computer 20 includes a CPU (Central Processing Unit) 21, a main storage device 22 that provides a temporary storage area, an auxiliary storage device 23 that provides a non-volatile storage area, and an input / output interface (I / F) 24. The CPU 21, the main storage device 22, the auxiliary storage device 23, and the input / output I / F 24 are connected to each other via the bus 25.

The auxiliary storage device 23 can be realized by a Hard Disk Drive (HDD), a Solid State Drive (SSD), a flash memory, or the like. The auxiliary storage device 23 stores a furnace residual slag amount estimation program 30 for causing the computer 20 to function as the furnace residual slag amount estimation device 10. The CPU 21 reads the in-core residual slag amount estimation program 30 from the auxiliary storage device 23, deploys it to the main storage device 22, and sequentially executes the process described in the in-core residual slag amount estimation program 30, so that the computer 20 can perform the computer 20. , It functions as a sedation characteristic estimation unit 11 and a furnace residual slag amount estimation unit 12.

Examples and comparative examples of the present invention will be described below.
However, the conditions of the examples are examples of the conditions adopted for confirming the feasibility and effect of the present invention, and the present invention is not limited to this example. Various conditions can be adopted as long as the gist of the present invention is not deviated and the object of the present invention is achieved.

(Example 1)
The test was carried out in a 350 ton scale top-bottom blown converter. The inner diameter of the furnace opening of the converter was about 4.6 m, the inner diameter of the straight body of the converter was about 6.6 m, and the distance from the upper end of the straight body to the furnace opening was about 2.7 m.

By numerical fluid calculation, the residual slag volume in the furnace was calculated with the shape of the converter and the assumed tilt pattern as input conditions. Based on this, an estimation formula (regression formula) was created for associating the tilt pattern in the converter with the residual slag volume in the furnace.

Next, the slag height is measured for 1 minute with a microwave range finder after the dephosphorization treatment and before the slag is discharged, the forming stagnation characteristics are estimated from the height change, and the slag is tilted during the subsequent tilting. The amount of slag remaining in the furnace was sequentially calculated for each minute time according to the rolling pattern, and the amount of slag remaining in the furnace (weight) was estimated.

An example thereof is shown in FIGS. 3A to 3C.
FIG. 3A shows the result of measuring the slag height with a microwave range finder before scavenging and estimating the forming sedative characteristics from the height change.
Here, the broken line in the figure is the result of slag height measurement for 1 minute by the microwave range finder, and the solid line is the parameter of the calculation model for estimating the forming sedation characteristic based on the measured value of the microwave range finder. The result.

FIG. 3B shows the tilt pattern (transition of tilt angle) of the converter. As shown in FIG. 3B, the converter is kept upright for the initial 1 minute, and the slag height is measured with a microwave range finder before the slag is discharged. After that, the tilting was started, and the tilting was performed so that the formed slag did not overflow from the slag pan, and the molten iron flowed out from the converter at about 83 °, so that the slag was completed.
FIG. 3C shows the time course of the residual slag amount (weight) in the furnace estimated from the estimated forming sedation characteristics (solid line in FIG. 3A) and the actual tilt pattern (FIG. 3B).

As shown in FIG. 3C, the estimated value of the residual slag amount (weight) in the furnace at the end of the slag is almost the same as the value calculated from the actual weighing value by the weighing device.
Here, the calculated value from the actual scale value was obtained by subtracting the actual scale value of the discharge amount from the amount of slag in the furnace before the discharge obtained by the mass balance calculation. The actual scale value is corrected to remove the amount of grain iron that is inevitably mixed in the slag. As a correction method, a part of the slag was sampled, the ratio of the grain iron contained in the slag was obtained, and the portion was subtracted from the actual scale value.
On the other hand, the method of the present invention does not require correction of the grain iron content.

Further, a plurality of tests were carried out, and the amount of residual slag in the furnace was compared with the calculated value from the actual scale value, the estimated value by the method of the present invention, the estimated value visually by the operator, and the estimated value by the method of Patent Document 1. The result of the above is shown in FIG.

In the method of Patent Document 1 referred to here, the volume of slag remaining in the furnace is estimated from the final tilt angle without considering the head portion of the slag flowing out, and the slag remains in the furnace. This is a method of estimating the bulk density of existing slag as constant.

When the average value (mean error) of the difference from the weighed value was calculated, it was 0.32 ton by the method of the present invention, 1.10 ton by the method visually observed by the operator, and 1.71 ton by the method of Patent Document 1.

It is probable that the reason why the estimated value by the operator's visual method was biased higher than the calculated value from the actual scale value was that the amount of residual slag in the furnace was overestimated in order to avoid the risk of component loss.

It is probable that the reason why the estimated value by the method of Patent Document 1 was biased to be lower than the calculated value from the actual scale value was that the bulk density of the residual slag in the furnace was estimated to be lower. However, as shown in FIG. 4, the estimated value by the method of Patent Document 1 is not only biased lower than the calculated value, but also has a large variation. That is, even if the bulk density of the residual slag in the furnace is estimated to be slightly higher, the bulk density is constant, so that the estimation result has a large variation.

On the other hand, the reason why the difference between the estimated value by the method of the present invention and the weighed value was small is considered to be that the present invention is an estimation method based on the following findings.
That is, according to the findings of the present invention, the residual slag in the furnace is a mixture of low-density slag and high-density slag, and the proportion of the residual slag changes as the forming stagnation characteristics and the tilt pattern change. It is also necessary to consider that the average bulk density of residual slag in the furnace also changes.
Further, according to the findings of the present invention, it is preferable to consider the head portion of the slag flowing out from the viewpoint of accuracy in estimating the volume of the slag remaining in the furnace.

As described above, according to the present invention, it is possible to easily and accurately estimate the amount of residual slag in the furnace.

(Example 2)
In Example 2, a test for evaluating the effect of reducing the amount of auxiliary raw materials used was carried out.
It was carried out using the same converter as in Example 1.
After charging the scrap and the hot metal, auxiliary raw materials such as quicklime were added so that the slag had a predetermined basicity according to the amount of the hot metal and the Si concentration, and the hot metal was dephosphorized. After that, the converter was tilted to remove a part of the upper slag from the furnace mouth, and then the converter was made upright again to add auxiliary materials, and the decarburization treatment was continued. At this time, the amount of residual slag in the furnace was estimated by the method of the present invention and the conventional method visually observed by the operator, and the amount of auxiliary raw material to be added during the decarburization treatment was determined.

Regarding the method for determining the amount of auxiliary raw material, the amount of CaO and the amount of SiO2 contained in the residual slag in the furnace were calculated from the composition of the residual slag in the furnace calculated from the material balance and the estimated amount of residual slag in the furnace. The weight concentration ratio of CaO and SiO2 in the slag during the decarburization treatment is (% CaO) / (% SiO2) so that the slag composition is suitable for preventing the components from coming off during the decarburization treatment. (To be within the proper range).

It was confirmed that the method of the present invention has an effect of reducing the amount of auxiliary raw materials used on average by about 420 kg per charge for steel grades having the same product phosphorus concentration level as compared with the conventional method. This corresponds to a cost improvement effect of about 25 yen per ton of molten steel.

1 Microwave distance meter 2 Measuring rod 3 Low-density slag layer 4 High-density slag layer 5 Molten iron 6 Converter 10 Residual slag amount estimation device in the furnace 11 Suffocation characteristic estimation unit 12 Residual slag amount estimation unit in the furnace 13 Residual volume transition estimation unit 14 Slag state estimation unit at the start of discharge 15 Sequential calculation unit

Claims (10)

In the operation of discharging slag from the furnace mouth while leaving molten iron in the converter by tilting the converter after desiliconization or dephosphorization in the converter, the amount of slag remaining in the furnace after the discharge is reduced. It ’s a method of estimation,
Step A in which the slag height in the converter is measured multiple times or continuously after the desiliconization or dephosphorization treatment and before the start of slag removal.
Step B, which estimates the forming sedative characteristics of the slag in the furnace based on the results measured in step A, and step B,
Step C, which estimates the amount of residual slag in the furnace based on the sedation characteristics estimated in step B and the tilt pattern of the converter,
A method for estimating the amount of residual slag in a furnace, which comprises. Process C is
Based on the sedation characteristics estimated in step B and the tilt pattern of the converter, step D in which the sedation behavior and the discharge behavior are sequentially calculated for each time step in which the time from the start of slag to the end of slag is divided by a minute time. The method for estimating the amount of residual slag in a furnace according to claim 1, wherein the method includes. Process C is
The method for estimating the amount of residual slag in a furnace according to claim 2, further comprising step E in which the slag state at the start of slag is estimated based on the sedation characteristics estimated in step B. Process C is
Step F for estimating the residual slag volume transition based on the tilt pattern of the converter, and
A claim comprising a sedative property estimated in step B and a step G for estimating sedative behavior and discharge behavior simultaneously progressing during slag based on the residual slag volume transition estimated in step F. Item 2. The method for estimating the amount of residual slag in the furnace according to Item 1. Process G is
Based on the sedation characteristics estimated in step B and the residual slag volume transition estimated in step F, the step of sequentially calculating the slag state for each time interval from the start time of slag discharge to the end time of slag discharge. The method for estimating the amount of residual slag in a furnace according to claim 4, wherein H is contained. Process G is
The method for estimating the amount of residual slag in a furnace according to claim 5, further comprising step I in which the slag state at the start of slag is estimated based on the sedation characteristics estimated in step B. The method for estimating the amount of residual slag in a furnace according to any one of claims 4 to 6, wherein in step F, the volume corresponding to the head portion of the slag flowing out is estimated. The method for estimating the amount of residual slag in a furnace according to any one of claims 1 to 7, wherein the step A is performed using a microwave range finder. In the operation of discharging slag from the furnace mouth while leaving molten iron in the converter by tilting the converter after desiliconization or dephosphorization in the converter, the amount of slag remaining in the furnace after the discharge is reduced. It is a device to estimate
A sedation characteristic estimation unit that estimates the forming sedation characteristics of the slag in the furnace based on the results of measuring the slag height in the converter multiple times or continuously after the desiliconization or dephosphorization treatment and before the start of scavenging.
The amount of residual slag in the furnace is characterized by comprising an in-core residual slag amount estimating unit that estimates the amount of residual slag in the furnace based on the sedation characteristics estimated by the sedation characteristic estimation unit and the tilt pattern of the converter. Estimator. The residual slag amount estimation unit in the furnace is
A residual volume transition estimation unit that estimates the residual slag volume transition based on the tilt pattern of the converter,
A slag state estimation unit at the start of slag that estimates the slag state at the start of slag based on the sedative characteristics estimated by the sedation characteristic estimation unit, and a slag state estimation unit at the start of slag.
Based on the sedation characteristics estimated by the sedation characteristic estimation unit and the residual slag volume transition estimated by the residual volume transition estimation unit, the period from the start of slag to the end of slag is divided by a minute time step. The device for estimating the amount of residual slag in a furnace according to claim 9, further comprising a sequential calculation unit for sequentially calculating the slag state.