JP7560731B2 - Preheating device and preheating method - Google Patents

Description

The present invention relates to a preheating device and a preheating method.

At steelworks, molten pig iron at about 1500°C produced in the blast furnace is discharged into a torpedo car (also called a torpedo car or mixed iron car) and transported to the steelmaking plant while contained inside the torpedo car, where it is transferred from the torpedo car to a ladle or other container. During this time, preliminary molten iron processing such as desiliconization may be carried out inside the torpedo car. The torpedo car that has transferred the molten pig iron returns to the blast furnace, where it picks up molten pig iron from the blast furnace and the above operation is repeated.

The inner walls of the torpedo car are made of refractory in order to handle the high-temperature molten iron. If this refractory becomes damaged due to repeated operation of the torpedo car, it is replaced. The new refractory is dried and preheated. Even if operation continues without replacing the refractory, the torpedo car, which has once cooled down, is preheated to protect the refractory when it is used again. This drying, preheating, and heat retention before operation are usually performed by inserting a burner through the torpedo car's iron receiving hole.

When burning with a burner, the amount of combustion gas, such as COG (coke oven gas), and the amount of air are adjusted to achieve an appropriate air ratio. During drying and preheating, the receiving hole is partially open to allow the burner to be put in and taken out and to allow the exhaust gas from the inside of the torpedo car to be discharged, and this causes problems such as heat loss due to the air entering and reducing the efficiency of the burner.

Patent Document 1 discloses a device for efficiently heating the inside of a torpedo car. In the device described in Patent Document 1, the torpedo car body is rotated so that the receiving nozzle is positioned to the side of the torpedo car body, a burner is inserted, and the bottom of the receiving nozzle is covered with a lid so that the opening of the receiving nozzle has a preset opening ratio when viewed from the side. By adjusting the opening ratio of the receiving nozzle with the lid covering the bottom of the receiving nozzle, it is possible to prevent outside air from entering and to exhaust combustion exhaust gas from above the open receiving nozzle. This enables efficient and uniform heating, reducing fuel consumption, shortening preheating time, and reducing costs.

International Publication No. 2018/186236

The refractory inside the torpedo car is heated not only after replacing the refractory, but also when a torpedo car whose temperature has dropped is used again, preheating is sometimes performed to protect the refractory. The receiving hole of a torpedo car that has been used repeatedly may have metal or the like attached irregularly. For this reason, in the case of a method in which a lid is pressed against the receiving hole as in Patent Document 1, even if the lid is pressed against the receiving hole whose flatness has been deteriorated by the metal, the lid portion may not close sufficiently, and the set opening rate may not be achieved. This may result in outside air entering, making it difficult to efficiently heat the refractory inside the torpedo car.

Therefore, one of the objects of the present invention is to provide a preheating device and a preheating method that efficiently preheats the refractory material inside the torpedo car.

In order to achieve the above object, a preheating device according to one aspect of the present invention comprises:
A preheating device for preheating a molten metal vessel of a molten metal car having a receiving hole and a molten metal vessel opening in a first direction, comprising:
A burner inserted into the receiving hole;
A cover having an insertion port for the burner and capable of closing the receiving port;
a movement control unit that moves the cover along the first direction based on an oxygen concentration in the molten metal container to change a relative position between the cover and the receiving hole;
Equipped with.

In order to achieve the above object, a preheating method according to one aspect of the present invention comprises the steps of:
A preheating method for preheating a molten metal vessel of a molten metal car having a receiving hole and a molten metal vessel opening in a first direction, comprising:
Inserting a burner into the receiving hole;
A lid having an insertion port for the burner and capable of closing the molten iron receiving hole is moved along the first direction based on the oxygen concentration in the molten iron container to change the relative position between the lid and the molten iron receiving hole.

According to the present invention, the refractory material inside the torpedo car can be preheated efficiently.

FIG. 1 is a diagram showing a preheating device according to an embodiment. FIG. 2 is a diagram showing the inside of a torpedo car being preheated by the preheating device of the embodiment. FIG. 3 is a diagram showing the inside of a torpedo car being preheated by the preheating device of the embodiment. FIG. 4 is a diagram showing the relationship between the elapsed time of preheating and the distance between the heat shield and the receiving hole. FIG. 5 is a diagram showing the relationship between the elapsed time of preheating and the oxygen concentration in the molten iron vessel. FIG. 6 is a diagram showing the relationship between the elapsed time of preheating and the temperature in the molten iron vessel. FIG. 7 is a diagram showing the relationship between the elapsed time of preheating and the amount of COG supplied.

Below, a preheating device according to one embodiment of the present invention and a preheating method using the preheating device will be described with reference to the drawings.

Figure 1 is a diagram showing the preheating device 1 of this embodiment. In Figure 1, the torpedo car 100 is shown in cross section as viewed from the side. Figures 2 and 3 are diagrams showing the inside of the torpedo car 100 being preheated by the preheating device 1 of this embodiment. Like Figure 1, Figure 2 is a cross section of the torpedo car 100 as viewed from the side, and Figure 3 is a cross section as viewed from above.

The torpedo car 100 is equipped with a molten iron vessel 101 having a substantially long cylindrical shape that contains molten iron produced in a blast furnace. The torpedo car 100 is equipped with a structure that rotates the molten iron vessel 101 around its longitudinal axis. The inner wall of the molten iron vessel 101 is lined with a refractory material 102 that can withstand high-temperature molten iron.

The torpedo car 100 is equipped with a receiving hole 103 that opens in a first direction (hereinafter referred to as the opening direction). The receiving hole 103 is an opening that connects the inside and outside of the molten iron vessel 101, and the molten iron is put in and taken out through the receiving hole 103. As shown in FIG. 3, the refractory material 102 is also applied to the inner wall of the receiving hole 103. When receiving molten iron from the blast furnace, the torpedo car 100 rotates the molten iron vessel 101 so that the opening direction is aligned with the vertical direction and the receiving hole 103 faces straight up, and when discharging the molten iron, rotates the receiving hole 103 so that it faces diagonally downward from the main body. In addition, when preheating using the preheating device 1 described below, the torpedo car 100 rotates the molten iron container 101 so that the opening direction is aligned horizontally and the receiving hole 103 faces straight to the side.

The preheating device 1 includes a burner 2, a heat shield 3, a burner movement unit 4, and a movement control unit 5.

Various burners except regenerative burners can be used for the burner 2. The burner 2 has a double-pipe structure with an air pipe 21 and a fuel pipe 22 arranged inside it, and the fuel (e.g., COG: coke oven gas) and air supplied through each pipe are mixed at the tip and burned. The burner 2 extends in the horizontal direction. The burner 2 can be moved in the horizontal direction by the burner movement part 4 described later. The tip of the burner 2 is adapted to be inserted and removed inside the molten iron vessel 101, whose opening direction of the receiving hole 103 coincides with the horizontal direction. The tip of the burner 2 is formed in a T-shape as shown in FIG. 3, and the flow paths for the fuel and air are branched at the tip of the T-shape.

The burner 2 is equipped with a sampling tube (not shown) for sucking in and sampling gas, and a thermocouple for measuring temperature. The sampling tube is a tube for sampling gas in the molten iron vessel 101 when the burner 2 is inserted into the molten iron vessel 101. The sampled gas is analyzed and used to measure the oxygen concentration in the molten iron vessel 101. The thermocouple is a thermometer for measuring the temperature in the molten iron vessel 101 when the burner 2 is inserted into the molten iron vessel 101.

The heat shield 3 is a heat-resistant cover that can cover the entire ferrous receiving port 103. The heat shield 3 can be moved horizontally by the movement control unit 5 described below. The heat shield 3 is adapted to move horizontally relative to the ferrous receiving port 103, whose opening direction coincides with the horizontal direction. The heat shield 3 is also provided with an insertion port 31 (see Figures 2 and 3) through which the burner 2 can be inserted. The burner 2 is adapted to move horizontally while inserted into this insertion port 31.

A buffer material 3A is provided on the surface of the heat shield 3 facing the receiving nozzle 103. When molten iron is received or discharged, metal may adhere to the receiving nozzle 103, causing unevenness and deteriorating the flatness of the receiving nozzle 103. If metal is adhered to the receiving nozzle 103, the heat shield 3 cannot be brought into close contact with the receiving nozzle 103 even if the heat shield 3 is to be brought into contact with the adhered metal, and a gap is created between the heat shield 3 and the receiving nozzle 103. Therefore, by providing the buffer material 3A, the gap can be eliminated. For example, a bracket made of ceramic fiber can be used as the buffer material 3A.

The burner moving unit 4 moves the burner 2 horizontally relative to the molten iron container 101, whose opening direction of the receiving nozzle 103 coincides with the horizontal direction. The burner moving unit 4 supports the burner 2 on a cart that moves on rails, for example, and moves the cart along the rails to move the burner 2 by transmitting the rotation of the drive motor to the cart via a burner drive chain via a pulley. Note that the method of moving the burner 2 is not limited to this.

The movement control unit 5 moves the heat shield 3 horizontally based on the oxygen concentration in the torpedo car 100 to change the relative position between the heat shield 3 and the receiving hole 103. The movement control unit 5 includes a rail 51, a cart 52 that supports the heat shield 3 and moves on the rail 51, a weight 53 placed on the cart 52, and a cylinder 54. The weight 53 is a counterweight placed on the side of the cart 52 opposite the side that supports the heat shield 3. The cylinder 54 moves the cart 52 along the rail 51 by pushing and pulling the weight 53 with its rod. The cylinder 54 is driven based on the oxygen concentration in the receiving hole 103. The cylinder 54 may be driven by an operator based on the oxygen concentration, or by a control device (not shown).

In addition, for example, if the deposits such as slag on the receiving nozzle 103 are too large and the gap between the heat shield 3 and the receiving nozzle 103 does not become smaller, there is a possibility that the equipment will remain in a state where the maximum mechanical load is applied. Therefore, for safety reasons, it is preferable that the movement control unit 5 is configured to stop the movement of the heat shield 3 when the pressing force when the heat shield 3 contacts the receiving nozzle 103 exceeds a predetermined value. The sensor that detects the pressing force may be provided on the heat shield 3 or on the receiving nozzle 103. The fact that the movement has stopped may also be notified by a screen display or by sound.

The preheating method using the preheating device 1 configured as described above is described below.

When the torpedo car 100 is positioned in the preheating device 1, the molten iron vessel 101 is rotated so that the opening direction of the receiving nozzle 103 coincides with the horizontal direction. Next, the tip of the burner 2 is moved into the molten iron vessel 101 with respect to the receiving nozzle 103 whose opening direction coincides with the horizontal direction. Then, the fuel and air are mixed at the tip and combusted in the molten iron vessel 101. At this time, the amount of air supplied from the air pipe 21 is controlled according to the amount of fuel supplied from the fuel pipe 22 so that the air ratio is 1 or less.

The air ratio is the ratio of the amount of air actually supplied from burner 2 to the stoichiometric amount of air required for complete combustion of the fuel supplied from burner 2. While a high air ratio guarantees complete combustion, the combustion progresses rapidly at the tip of burner 2, and the flame does not reach the entire molten iron vessel 101, resulting in insufficient heating. Therefore, by setting the air ratio to 1 or less, the flame becomes longer and heat can be transferred to the entire molten iron vessel 101 without the combustion progressing too rapidly.

After combustion begins, the gas in the molten iron vessel 101 is sucked in through a sampling tube attached to the burner 2, sampled, and analyzed to measure the oxygen concentration in the gas. The heat shield 3 is then moved relative to the receiving nozzle 103 so that the oxygen concentration becomes a preset value. More specifically, if the oxygen concentration in the molten iron vessel 101 is higher than a preset target value, the heat shield 3 is moved closer to the receiving nozzle 103. If the oxygen concentration in the molten iron vessel 101 is lower than the target value, the heat shield 3 is moved away from the receiving nozzle 103.

The receiving hole 103 is not sealed because the heat shield 3 is moved. For this reason, air entering through the receiving hole 103 during preheating is unavoidable. As described above, the fuel supply is controlled so that the air ratio is 1 or less. However, because oxygen from the entering air also contributes to combustion, setting the air ratio to 1 or less does not necessarily mean that the fuel will burn incompletely. Also, if the amount of entering air is too small, the fuel will burn incompletely, reducing preheating efficiency and possibly worsening the working environment. On the other hand, if the amount of entering air is too large, the fuel will burn completely, but the preheating efficiency will deteriorate due to cooling by the entering air. For this reason, it is necessary to adjust the amount of entering air appropriately.

Whether the amount of air entering the molten iron vessel 101 is appropriate can be determined by the oxygen concentration inside the molten iron vessel 101 during preheating. A target value for the oxygen concentration is set in advance, and the actual measured oxygen concentration is compared with the target value to control the measured value to approach the target value. If the oxygen concentration is higher than the set value, this indicates that a large amount of air is entering the vessel, so the gap between the heat shield 3 and the receiving hole 103 is narrowed. This reduces the amount of air entering the molten iron vessel 101. Conversely, if the oxygen concentration is lower than the set value, there is a high possibility of incomplete combustion, so the gap between the heat shield 3 and the molten iron vessel 101 is widened. This increases the amount of air entering the molten iron vessel 101.

In this way, by changing the distance between the heat shield 3 and the receiving hole 103 based on the oxygen concentration inside the molten iron vessel 101, the amount of air entering can be appropriately adjusted, and combustion in the molten iron vessel 101 can be carried out efficiently.

The results of tests conducted on the present invention are shown below. In the following, the fuel supplied from burner 2 is COG.

In this test, the amount of COG supplied to the molten iron container 101, which was about 300°C, was controlled so that the heating rate was 100°C/h until the temperature inside the furnace reached 800°C. After the temperature inside the furnace reached 800°C, the amount of COG supplied was controlled so that the temperature was kept at 800°C. The oxygen flow rate was also controlled so that the air ratio was 0.9. The air ratio was calculated from the amount of COG and air supplied to the burner 2, and oxygen from air entering through the receiving hole 103, etc., was not calculated.

In addition, in this test, frequent adjustment of the heat shield 3 could potentially destabilize the combustion state, so the movement of the heat shield 3 was controlled so that it was moved closer to the receiving nozzle 103 when the oxygen concentration exceeded 2%, and moved away from the receiving nozzle 103 when the oxygen concentration fell below 1%. Normally, CO is not generated when the oxygen concentration exceeds 2%. There are cases where CO is not generated even when the oxygen concentration falls below 1%, but the lower limit was set to 1% as a control. Furthermore, when the CO concentration reached 0.01%, the heat shield 3 was moved away from the receiving nozzle 103 until the CO disappeared.

In this way, the temperature, oxygen concentration, and COG supply amount into the molten iron vessel 101 were measured for preheating the molten iron vessel 101 by controlling the COG supply amount and oxygen flow rate and controlling the movement of the heat shield 3.

As a comparative example, the distance between the heat shield 3 and the receiving hole 103 was fixed at 150 mm, and the temperature, oxygen concentration, and amount of COG supplied to the molten iron vessel 101 were measured in the same manner. This distance of 150 mm was set to avoid CO gas generation even at the most vigorous stage of combustion.

Figure 4 is a diagram showing the relationship between the elapsed time of preheating and the distance between the heat shield 3 and the receiving hole 103 (distance between the heat shields). Figure 5 is a diagram showing the relationship between the elapsed time of preheating and the oxygen concentration in the molten iron vessel 101. Figure 6 is a diagram showing the relationship between the elapsed time of preheating and the temperature in the molten iron vessel 101. Figure 7 is a diagram showing the relationship between the elapsed time of preheating and the amount of COG supplied. Note that the values (1) to (8) in Figures 4 to 7 are each values measured at the same time during the elapsed time. The values (1) to (8) are shown in Table 1. Table 1 also shows the CO concentration.

From Figure 6, it can be seen that the temperature in the molten iron container 101 reaches 800°C more quickly in the present invention than in the comparative example.

In addition, when comparing (1), (2), and (4) of the present invention with (5), (6), and (8) of the comparative examples, it can be seen that the amount of COG supplied in the present invention is reduced more than in the comparative examples. This is because in the cases of (1), (2), and (4) of the present invention, the heat shield 3 is closer to the receiving hole 103 than in the comparative examples (5), (6), and (8), so the amount of air that enters is suppressed.

Furthermore, in the present invention, as can be seen from a comparison between (3) and (7) in Table 1, it was confirmed that the generation of CO gas can be avoided by controlling the oxygen concentration to exceed 1%.

As described above, according to the preheating device 1 of this embodiment, by moving the heat shield 3 relative to the receiving port 103, fuel can be reduced and the inside of the torpedo car, specifically the refractory material 102 inside the molten iron container 101, can be efficiently preheated.

Reference Signs List 1 Preheating device 2 Burner 3 Heat shield 3A Cushioning material 4 Burner moving part 5 Movement control part 21 Air pipe 22 Fuel pipe 31 Insertion port 51 Rail 52 Cart 53 Weight 54 Cylinder 100 Torpedo car 101 Molten iron container 102 Refractory material 103 Iron receiving hole

Claims (7)

A preheating device for preheating a molten metal vessel of a molten metal car having a receiving hole and a molten metal vessel opening in a first direction, comprising:
A burner inserted into the receiving hole;
A cover having an insertion port for the burner and capable of closing the receiving port;
a movement control unit that, after starting combustion by the burner inserted in the receiving hole, moves the lid along the first direction based on the oxygen concentration in the molten iron container to change a relative position between the lid and the receiving hole;
A preheating device comprising: When the predetermined oxygen concentration is set to the set concentration, the movement control unit:
When the oxygen concentration is lower than the set concentration, the cover is moved in a direction relatively away from the receiving hole;
When the oxygen concentration is greater than the set concentration, the cover is moved in a direction relatively closer to the receiving hole.
The preheating device according to claim 1 . a burner moving unit that moves the burner relative to the molten iron vessel that is rotated so that the first direction coincides with a horizontal direction;
The preheating device according to claim 1 or 2, comprising: The movement control unit is
When the pressing force when the cover contacts the receiving hole exceeds a predetermined value, the movement of the cover is stopped.
The preheating device according to any one of claims 1 to 3. The burner is
An air pipe for supplying air;
A fuel pipe for supplying combustion gas;
having
an amount of air supplied from the air pipe is controlled in accordance with an amount of fuel gas supplied from the fuel pipe so that an air ratio is equal to or less than 1;
The preheating device according to any one of claims 1 to 4. The cover has a cushioning material on a surface facing the receiving hole.
The preheating device according to any one of claims 1 to 5. A preheating method for preheating a molten metal vessel of a molten metal car having a receiving hole and a molten metal vessel opening in a first direction, comprising:
Inserting a burner into the receiving hole;
a cover having an insertion port for the burner and capable of closing the receiving port is moved along the first direction based on an oxygen concentration in the molten iron container after starting combustion by the burner inserted in the receiving port , thereby changing a relative position between the cover and the receiving port.
Preheating method.

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