JP2021188097A - Mechanical stirring desulfurization system - Google Patents

Abstract

To provide a mechanical stirring desulfurization system capable of detecting a molten metal surface level of molten iron by a simple method and automatically adjusting a lance to an optimum position according to the detected molten metal surface level of molten iron.SOLUTION: A mechanical stirring desulfurization system includes a control part 14 for controlling movement so that a tip of an upper blowing lance 10 is positioned at a predetermined height from a molten metal surface of a molten metal ladle 2. The control part 14 includes: moving distance calculating means for calculating a free board ΔH of the molten metal ladle 2 from a tilt angle of the molten metal ladle 2 and an inner diameter D of the molten metal ladle 2 at the time of slag removal processing which is a pretreatment of desulfurization processing, and calculating a moving distance L of the upper blowing lance based on the calculated free board; and lance driving means for driving the upper blowing lance 10 so that the tip of the upper blowing lance is positioned at a predetermined height from the molten metal surface of the molten metal ladle 2 based on the calculated moving distance L.SELECTED DRAWING: Figure 7

Description

The present invention relates to a mechanically agitated desulfurization system including a mechanically agitated desulfurization apparatus and a gas blowing lance for blowing a desulfurizing agent into the mechanically agitated desulfurization apparatus.

As a typical equipment used for dephosphorization / desulfurization of hot metal, a dephosphorization / desulfurization agent is put into a smelting container containing hot metal, and the hot metal is mechanically stirred using a stirring impeller. Mechanically agitated desulfurization equipment is known.

In such equipment, the gravity drop method has been conventionally adopted as the method for adding the desulfurizing agent, but in that method, a part of the desulfurizing agent is scattered and sucked into the dust collector at the time of addition, or desulfurization is performed. Since the agent aggregates and the desulfurization efficiency decreases, there is a problem that the yield of adding the desulfurization agent or the like is low.
Therefore, a desulfurizing agent is continuously sprayed onto the bath surface of the agitated hot metal at high speed using a transport gas such as argon gas or nitrogen gas via a cylinder called a top-blown lance. A method of invading and adding (see, for example, Patent Document 1) has come to be used.

Japanese Unexamined Patent Publication No. 2005-179690 Japanese Unexamined Patent Publication No. 2004-301362

In the method of spraying the desulfurization agent on the hot water surface of the hot metal using such a top blowing lance, the height of the lance with respect to the hot water level greatly contributes to the desulfurization efficiency.
For example, at the time of projection, if the distance between the lance and the molten metal surface is long (800 mm or more), it is sucked by the dust collector and the amount of desulfurization agent charged decreases, so that the desulfurization efficiency deteriorates. On the contrary, if the distance between the lance and the surface of the molten metal is short (400 mm or less), the tip of the lance will be melted by the hot metal and the service life of the lance will be shortened.
Therefore, it is important to adjust the height of the lance with respect to the level of the molten metal (recommended lance ~ height of the molten metal: 500 to 700 mm).

In addition, the amount of hot metal differs for each treatment, and the shape of the treatment pot varies greatly with each treatment due to the bare metal adhering to the inside of the pot, so it is necessary to measure the hot water level every time.
Conventionally, the following methods are known as methods for measuring the hot water level of hot metal.
(1) A method of dividing the weight of the hot metal by the specific gravity to obtain the volume, and dividing it by the bottom area of the hot metal pot to obtain the height (hot water level). If the bottom area is attached, the bottom area becomes small, or conversely, if the inside of the pot is worn, the bottom area becomes large, so that there is a problem that the accuracy is not very good.

(2) A method of measuring the molten metal level using a sensor that transmits and receives microwaves from the opening direction of the upper part of the hot metal pot. It is necessary to take heat-resistant measures such as inserting it to surround the sensor and suppressing the temperature rise inside, but when dust such as desulfurization agent introduced in the desulfurization process rises and adheres to and accumulates on the heat-resistant board, the microwave is attenuated. , There was a problem that the molten metal level could not be measured.

(3) A method of determining the change in the brightness of the molten metal surface when the stirring impeller is immersed in the hot metal by visual inspection or by imaging with a camera. However, in the case of visual inspection, the operator must constantly monitor the molten metal surface. There is a problem in terms of load and labor saving. Further, in the determination by the camera, there is a problem that the detection accuracy varies depending on the properties of the slag floating on the surface of the hot metal, the amount of slag generated, and the state of distribution. Furthermore, there is a high risk of camera failure due to the surrounding environment.

In view of the conventional problems, the splash generated at the moment when the tip of the stirring impeller touches the hot water surface of the hot metal is detected, and the hot metal level is measured from the value of the encoder installed on the motor shaft for raising and lowering the stirring impeller at that time. A method has been proposed (see Patent Document 2).
However, this method inevitably has the problem that the generated splash wears the refractory material in the hot metal pot, the steelmaking yield is lowered, and the surveillance camera that detects the splash is liable to break down at high temperature.
The present invention has been made in view of the above-mentioned problems, the molten metal level is detected by a simple method, and the lance is automatically adjusted to the optimum position according to the detected molten metal level. It is an object of the present invention to provide a mechanically agitated desulfurization system capable of performing.

The present invention comprises a mechanically agitated desulfurization apparatus (hereinafter referred to as "desulfurization apparatus") equipped with a stirring impeller and a hot metal pan, and a top blowing lance for projecting a desulfurizing agent onto the hot metal pan of the desulfurization apparatus. With respect to the mechanical stirring type desulfurization system for desulfurizing the hot metal charged into the hot metal, the object of the present invention is that the tip of the top blowing lance is at a predetermined height (H) from the hot water surface of the hot metal pan. Further, a control unit that controls movement so as to be in a position is further provided, and the control unit includes a tilt angle (θ) of the hot metal pot during the slag removal treatment, which is a pretreatment of the desulfurization treatment, and an inner diameter (D) of the hot metal pot. ), The free board (ΔH) of the hot metal pan is calculated, and the moving distance (h) of the upper blowing lance is calculated based on the calculated free board, and the moving distance is calculated based on the calculated moving distance. The mechanical stirring is provided with a lance driving means for driving the top blowing lance so that the tip of the top blowing lance is at a predetermined height (H) from the hot water surface of the hot metal pot. Achieved by a formula desulfurization system.

According to the mechanical stirring type desulfurization system according to the present invention, it is possible to detect the molten metal level at a simple method and automatically adjust the lance to the optimum position according to the detected molten metal level. Become.

It is a figure which shows the state of the pretreatment of the desulfurization treatment. It is a figure which shows the drive system for tilting a hot metal pot. It is a figure which shows the general desulfurization treatment system. It is a figure for demonstrating the method of obtaining the height ΔH of the freeboard part of a hot metal pan from the tilt angle (θ) stored in the pretreatment. The figure shows the case where metal adheres to the refractory inside the hot metal pot and the inner diameter D becomes narrower (Fig. A), and the case where the inner refractory wears and the inner diameter D becomes wider (Fig. B). be. This is a graph of the relationship between the tilt angle (θ) and the freeboard. It is a schematic diagram which shows the structure of the mechanical stirring type desulfurization system which concerns on this invention. The relationship between the tilt angle (θ) and the freeboard is tabulated for each state of wear of the pot. This is an example of a flowchart showing the flow of control performed by the control unit.

Hereinafter, the mechanically stirred desulfurization system (hereinafter, simply referred to as “desulfurization system”) according to the present invention will be described in detail with reference to the drawings.
In general, a mechanically agitated desulfurization process (hereinafter simply referred to as "desulfurization process") desulfurizes hot metal in a pretreatment, desulfurization treatment, and posttreatment procedure.
The pretreatment is a step of removing slag floating on the surface of the molten metal with a slag skimmer in order to increase the desulfurization efficiency before the desulfurization treatment.
FIG. 1 is a diagram showing a state of preprocessing.
(a) On the tilting carriage 1, tilt the hot metal pot 2 to the maximum angle so that the hot metal does not spill. The tilt angle θ at this time is stored in a storage device (not shown).
(b) The slag floating on the surface of the hot water is scraped off by the slag drainer 3 and transferred to the slag pot 4. After removing the slag, restore the inclination of the hot metal pot and move on to the next process.

FIG. 2 is a diagram showing a drive system for tilting the hot metal pot 2. FIG. 2A shows a case where the actuator 5 for driving the tilting of the hot metal pan 2 is electric, and the rotor is installed on the shaft of the tilting gear. (B) is a diagram showing the case where the actuator 5 is hydraulically driven, and the tilt angle changes as the hydraulic cylinder rod expands and contracts. Each has an encoder (not shown) and converts a mechanical displacement amount (angle change or expansion / contraction amount) into an electric signal. The output signal of the encoder is stored in a storage means (not shown), and the tilt angle can be known by reading the signal.

Next is the desulfurization process. FIG. 3 is a diagram showing a general desulfurization treatment system. The desulfurization treatment system includes a carriage provided with a stirring impeller 6, a rotary drive motor 7 of the stirring impeller 6, and an elevating frame body 8 in which a rotary drive motor 7 is installed to raise and lower the stirring impeller 6 up and down. A hot metal stirring unit equipped with an elevating motor 9 for pulling the elevating frame with a rope, and a desulfurizing agent at high speed using a transport gas such as argon gas or nitrogen gas on the bath surface of the agitated hot metal. A lance drive having a top blowing lance 10 (hereinafter referred to as "lance") for continuously spraying and adding, and a lance drive motor 11 for adjusting the height of the lance blowing port by moving the lance 10 up and down in the direction of the arrow in the figure. It is equipped with a lance projection unit provided with means, and a hot metal pot 2 that is placed on a tilting carriage 1 and into which hot metal is put.
The dust collector 12 is a device that collects the desulfurizing agent sprayed from the lance 10 that does not reach the hot metal pot 2 and is scattered in the air.

The desulfurization treatment is a treatment in which the desulfurization agent is projected and stirred in the hot metal to react the sulfur content in the hot metal with the desulfurization agent.
The process is as follows.
(a) The elevating motor 9 is driven, the stirring impeller 6 is lowered to a predetermined height together with the elevating frame body 8, immersed in the hot metal, and the hot metal is agitated by the rotary driving motor 7.
(b) After the lance 10 descends according to the molten metal level, the desulfurization agent is projected from the tip of the lance, the desulfurization agent is stirred and mixed with the hot metal, and the desulfurization reaction is started.
(c) When stirring is stopped, the desulfurizing agent combined with the sulfur component in the hot metal floats on the surface of the hot metal as a slag. Here, the lifting motor 9 is driven to lift the impeller 6 from the hot metal pan 2, and the process proceeds to the next post-processing.
The post-treatment is a step of removing the slag floating on the surface of the molten metal after the desulfurization treatment, and the operation is a step of tilting the hot metal pot 2 and removing the slag with the removing machine 3 as in the pre-treatment. .. Since the operation is basically the same as the preprocessing, detailed description is omitted.

In FIG. 3, the distance H between the lance and the molten metal surface becomes a problem, but normally, when H is approximately 400 mm or less, the tip of the lance may be melted by the hot metal or the splash of hot metal, and vice versa. If it is approximately 800 mm or more, the desulfurizing agent may be scattered and sucked into the dust collector 12, and the amount of the desulfurizing agent charged may be reduced.
Therefore, normally, the position of the tip of the lance is adjusted so that about 500 mm ≤ H ≤ about 700 mm, but the factor that affects the position adjustment of the lance is the freeboard part, which is the part that is not immersed in the hot metal. Height (ΔH).
Therefore, if this ΔH can be known in advance, it can be adjusted to an appropriate H.

FIG. 4 is a diagram for explaining a method of obtaining the height ΔH of the freeboard portion of the hot metal pot from the tilt angle (θ) stored in the pretreatment.
FIG. 4A is a diagram for a cylindrical container. Assuming that the tilt angle when tilted to the maximum angle so that the hot metal does not spill is θ and the diameter of the container is D, the volume V of the space inside the container can be expressed by the following equation.
V = (D / 2) ² × π × ΔH ₀ × (1/2)
Since the amount of hot metal in the pot does not change even if the tilt is restored, the volume of the space in the freeboard part does not change either. Therefore,
V = (D / 2) ² × π × ΔH
∴ (D / 2) ² × π × ΔH ₀ × (1/2) = (D / 2) ² × π × ΔH
∴ΔH = ΔH _0/2
However, obviously
ΔH ₀ = D × tan θ
Because it is
∴ΔH = (D × tanθ) / 2… (Equation 1)
Will be.
Therefore, ΔH is uniquely determined from the diameter D of the pot and the tilt angle θ, and does not depend on the amount of hot metal.

Next, FIG. 4 (B) is a diagram showing the case of an actual hot metal pan, but it is considered to be the same as that of the cylindrical container of (A) in which the notch of the portion shown by the dotted line is provided. ) Can be considered in the same way.
From the tilt angle (θ) stored in the pretreatment, the height ΔH of the freeboard portion of the hot metal pot can be obtained by using the above equation 1.

What affects the change in the inner diameter D of the hot metal pot is the degree of wear of the refractory material due to the frequency of use of the hot metal pot or the narrowing of the inner diameter D due to the adhesion of the metal. Normally, both of these are combined to change D.
FIG. 5 shows a case where a metal deposit adheres to the refractory inside the hot metal pot and the inner diameter D becomes narrow (Fig. A), and a case where the refractory inside is worn and the inner diameter D becomes wide (Fig. B). ).
Therefore, it is examined how much the freeboard ΔH is affected by the change in the inner diameter D.
Now, when the freeboard ΔH'when D changes by ΔD is calculated using the above equation 1,
ΔH'= (D + ΔD) × tanθ / 2 = Dtanθ / 2 + ΔDtanθ / 2
∴ΔH'= ΔH + ΔDtanθ / 2 ... (Equation 2)

Now, assuming that ΔD is a maximum of 200 mm (a wear of 100 mm as the thickness of the refractory and a wear of 200 mm on a diameter basis), the increase in ΔH (δ) is
δ = 100tanθ (mm)
Will be. When θ is 30 °, 40 °, and 45 ° (usually, the tilt angle is about 30 ° and the maximum is about 45 °), δ is calculated as follows.
tan30 ° = 0.58 δ = 58mm
tan 40 ° = 0.84 δ = 84mm
tan45 ° = 1 δ = 100mm
That is, even if the inner diameter of the freeboard pot changes by 200 mm, the freeboard base has an error of only 100 mm even when the tilt angle is up to 45 °, and even when compared with the width of the preferred freeboard range (500 mm to 700 mm). The impact is considered to be small.

FIG. 6 is a graph showing the relationship between the tilt angle (θ) and the freeboard. If the tilt angles are the same, it is visually shown that the effect of wear of the hot metal pot is small.
For example, at the location indicated by the arrow in the figure (θ = about 36 °), the case where there are 6 types of freeboard wear is displayed, but the range of the difference between those freeboards is within 100 mm. You can see that there is. Therefore, even if the freeboard calculated using the inner diameter D of a standard hot metal pot (for example, a new pot) is applied in all cases, it is considered that the influence is small.

Next, the configuration of the desulfurization system according to the present invention and its operation will be described.
FIG. 7 is a schematic diagram showing the configuration of the desulfurization system according to the present invention. Since the basic configuration is the same as that shown in FIG. 3, only the different parts will be described.
The desulfurization system according to the present invention is a conventional desulfurization system shown in FIG. 2 to which a lance passage detection sensor 13 (photoelectric sensor) and a control unit 14 for controlling the movement distance of the lance by a lance drive motor 11 are added. ..
The tilt angle θ is measured at the stage of preprocessing, input to the control unit 14, and stored. Further, as for the state of wear of the pot, the inner diameter D may be actually measured before the start of the pretreatment and the value may be input, or the degree of wear can be empirically known in advance by the number of times the pot is used. If so, you may enter the number of times it has been used and convert it to the degree of wear (mm).

The control unit 14 automatically controls the position of the tip of the lance from the molten metal surface to a predetermined height (H) and stops there. For that purpose, the lance must be moved to that position, and the descent distance L (pointing to the vertical distance after passing through the lance passage detection sensor 13) is obtained by the following equation. That is, if the height from the upper end of the pot to the lance passage detection sensor 13 is L ₀ and the free board of the pot is ΔH, then
L + H = L ₀ + ΔH
Because it becomes
∴L = L ₀ + ΔH−H ・ ・ ・ (Equation 3)
Since _{the value of L 0} is known in advance and about 500 mm ≦ H ≦ about 700 mm, for example, by setting H = 600 mm, L becomes a linear function of ΔH.
Therefore, by calculating the freeboard ΔH based on the tilt angle θ by the above equation 1, the lance can be automatically moved to the optimum position.

When the vertical inclination of the lance is α, the relationship between the descent distance L at the tip of the lance and the actual movement distance h in the traveling direction of the lance is
L = hcosα
It is represented by. That is,
h = Lsecα ... (Equation 4)
Will be. By moving the lance in the traveling direction by the distance of h, it is possible to move the lance by the desired descent distance L as a result.
The movement distance h in the traveling direction of the lance can be detected by combining a photoelectric sensor and a lance elevating / rotating device (encoder) (not shown).
The position where the lance blocks the photoelectric sensor 13 is measured by the elevating rotary device (encoder), and the moving distance from the position is measured by the encoder.
Also, instead of using an encoder, it is possible to set a scale reference next to the lance and read the scale with a camera to measure the length.

In order to reduce the influence of the freeboard ΔH pot wear state, the relationship between the freeboard value calculated in advance for each wear state and the tilt angle should be tabulated in advance, and the table should be switched as necessary. Is also one method.
FIG. 8 is a table showing the relationship between the tilt angle (θ) and the freeboard for each worn state of the pan. This is just an example. It is more accurate to set the angle in increments of once, but due to space limitations, it is displayed in increments of 5 °. It can be seen that if the angles are the same, the change in the freeboard ΔH due to the wear state is small.
For example, if the tilt angle is 30 °, the freeboard will only change by 58mm, even if it wears 100mm. In addition, even at 45 °, even if the freeboard wears 100 mm, the freeboard changes only 100 mm, and it can be seen that the effect is small even when compared with the width of the preferable freeboard range (500 mm to 700 mm).

FIG. 9 shows an example of a flowchart showing the flow of control performed by the control unit 14.
As a premise, the wear state (wear degree) of the hot metal pot used on the day and the tilt angle (θ) measured in the pretreatment are input and stored in advance.
When the program of the control unit 14 is started, first, the CPU (not shown) of the control unit 14 reads out the degree of wear (or the number of times of use) of the hot metal pot based on a predetermined program (S1). Next, the tilt angle θ is read out (S2). The freeboard ΔH corresponding to the tilt angle θ is read out with reference to a table of the freeboard corresponding to the degree of wear of the freeboard pot (for example, the table shown in FIG. 8) (S3).

The descent distance L of the lance is calculated based on the read freeboard ΔH (S4). The above equation 3 is used to calculate the descent distance L of the lance. Then, the moving distance h of the lance is calculated using the above equation 4.
The lance drive motor 11 is driven to start driving the lance (S5). When the lance passes through the lance detection sensor 13 (YES in step S6), the measurement of the moving distance of the lance is started (S7). The elevating rotary device (encoder) measures the moving distance from the time when the lance blocks the photoelectric sensor 13.
When the moving distance of the lance reaches the moving distance h obtained by the above equation 4 (YES in step S8), the driving (moving) of the lance is stopped (S9).
At the position where the lance is stopped, the projection of the desulfurizing agent from the lance is started (S10).

According to the present invention, the distance between the desulfurizing agent projection lance and the molten metal surface can be made constant in all treatments, and the optimum distance can be uniformly secured under any condition. As a result, the desulfurizing agent is not sucked into the dust collector, and the desulfurizing agent efficiently enters the inside of the agitated hot metal, enabling stable desulfurization treatment. This effect makes it possible to greatly increase the success rate of desulfurization treatment.
Further, the amount of melting damage at the tip of the lance due to the approach to the hot metal surface is reduced, and the service life of the lance pipe can be significantly extended.

1: Tilted block fault, 2: Hot metal pan, 3: Dust collector, 4: Slug pan, 5: Actuator, 6: Stirring impeller, 7: Rotation drive motor, 8: Elevating frame, 9: Elevating motor, 10 : Top blow lance, 11: lance drive motor, 12: dust collector, 13: lance passage detection sensor, 14: control unit

Claims (2)

It was equipped with a mechanical stirring type desulfurization device (hereinafter referred to as "desulfurization device") equipped with a stirring impeller and a hot metal pan, and a top blowing lance for projecting a desulfurizing agent onto the hot metal pot of the desulfurization device, and was charged into the hot metal pot. In a mechanically agitated desulfurization system that desulfurizes hot metal, the system is
Further, the control unit is provided with a control unit that controls the movement so that the tip of the top-blowing lance is located at a predetermined height from the hot water surface of the hot metal pan.
The free board of the hot metal pan is calculated from the tilt angle of the hot metal pan and the inner diameter of the hot metal pan during the slag removal treatment, which is the pretreatment of the desulfurization treatment, and the movement of the top blow lance is calculated based on the calculated free board. Based on the moving distance calculating means for calculating the distance and the calculated moving distance, the upper blowing lance is driven so that the tip of the upper blowing lance is at a predetermined height from the hot water surface of the hot metal pan. A mechanically agitated desulfurization system characterized by having a lance drive means to perform. The moving distance calculation means of the control unit is provided with a table in which the tilt angle and the freeboard are related to each degree of wear of the hot metal pot, and is obtained by using the table corresponding to the input degree of wear. The mechanically agitated desulfurization system according to claim 1, wherein the moving distance of the top blown lance is calculated based on the freeboard.

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