JP4979209B2 - How to adjust furnace profile - Google Patents

Description

  The present invention relates to a furnace body profile adjusting method in which, for example, a contour shape of an inner wall of a furnace body in a converter is adjusted by a refractory.

Conventionally, as shown in Patent Document 1, in the operation of a converter, hot metal is charged into the furnace body, a lance for up-blowing is inserted into the furnace port of the furnace body, and then oxygen is directed from the lance toward the hot metal. Blowing is performed by blowing gas. At this time, in the operation of the converter, gas is blown from the bottom of the furnace body, and oxygen gas is blown while stirring the molten iron.
When oxygen gas is blown from the lance, the oxygen gas collides with the surface of the hot metal, so a part of the hot metal becomes spitting iron and flies to the furnace mouth, and the spitting iron particles adhere to the furnace mouth. The bullion (hereinafter, the bullion attached to the furnace port is called the attached bullion).

For example, when charging scrap into the furnace body, the scrap chute that puts the scrap into the furnace body is clogged in the furnace mouth, because the adhering metal around the furnace mouth is deposited and deposited. This causes a problem that scrap cannot be put into the furnace.
Further, when a sub lance for measuring the temperature [° C.] of hot metal (molten steel) is inserted into the furnace body, there is a risk that the sub lance will collide with the adhered metal. Also, as the number of charges increases, the refractory at the bottom of the furnace body (furnace bottom) melts and decreases, and as a result, the vicinity of the furnace port gradually becomes heavier, and a tilting trip that makes it difficult for the converter to start up may occur. There is.

In this way, depositing ingots around the furnace mouth causes various problems, so when operating the converter, as much as possible to prevent spitting granulated iron from adhering to the furnace mouth. It is good to do.
JP 2005-89839 A

Therefore, a technique for preventing spitting granular iron from adhering to the furnace port by improving the lance tip has been considered, but the actual situation is that a sufficient effect has not been obtained.
As another method for preventing spitting granular iron from adhering to the furnace port, when the converter is operated, the distance from the hot metal surface to the furnace port (height in the furnace) is secured, and oxygen gas is blown in. In addition, it is conceivable to prevent spitting granular iron from reaching the furnace port.
In this method, if the height in the furnace is increased too much, that is, if the amount of hot metal put into the furnace is suppressed, the productivity is lowered. Moreover, if the furnace height is made too low, that is, if the amount of hot metal put into the furnace is increased, the productivity is improved, but there is a problem that spitting granular iron adheres to the furnace mouth. It is unresolved whether it should be made to the extent.

In addition, the furnace height increases as the number of charges increases because the refractory accumulated in the furnace body melts and peels and the inner diameter and depth of the furnace body increase as the number of charges increases. Therefore, in order to determine the height of the furnace body, it is necessary to consider the change in the height of the furnace body.
Then, an object of this invention is to provide the profile adjustment method which makes it difficult to adhere the spitting granular iron used as adhesion metal to a furnace port in view of the said problem.

In order to achieve the above object, the present invention has taken the following measures. That is, the technical means for solving the problem in the present invention is that, when 80 to 250 tons of main raw material is charged into the furnace body of the converter having the top bottom blowing function, the equations (1) to (3) are expressed. In order to satisfy, the inner wall contour shape of the furnace body is adjusted.

By doing in this way, it becomes difficult for spitting granular iron used as adhesion metal to adhere to a furnace mouth, the deposition rate (growth rate) of adhesion metal near the furnace mouth can be reduced, and adhesion metal Removal work can be reduced.
The inner wall contour shape of the furnace body is preferably adjusted by changing the thickness of the refractory provided in the furnace body.
The way of deriving equations (1) to (3) will be described with reference to FIGS.

  First, the variables used will be described. As shown in FIG. 1, the furnace height Hi in the furnace body of the converter is defined as the distance from the furnace port to the molten metal surface. Specifically, the furnace height Hi is the distance from the molten metal surface to the furnace opening when the main raw materials such as hot metal, cold iron, waste, and iron scrap are charged into the furnace body. The straight body portion inner diameter D of the furnace body is defined as a distance (inner diameter) between the refractories when the refractory is provided in the straight body portion of the furnace body. Further, the furnace body height H is a distance from the upper surface of the refractory provided at the bottom of the furnace body to the furnace mouth, and the furnace mouth inner diameter R is the inner diameter of the end of the throttle part of the furnace body, that is, the endmost part of the throttle part ( The inner diameter (distance) between the refractories provided at the furnace port edge.

As shown in FIG. 2, the in-furnace holding volume Vi is a molten steel volume (in other words, hot metal volume) that can be held by the furnace body when the furnace body is tilted by 90 ° toward the steel output side, that is, the furnace body is turned out. When tilted 90 ° to the side, the volume should be such that slag and molten steel are not emitted from the furnace port. The furnace volume Vo is the total volume in the furnace body.
Hereinafter, a specific derivation method will be described.
The inventor collected adhering metal adhering to the furnace port in the past operation, and as a result of performing cross-sectional area and composition analysis, the one having a particle diameter of spitting granular iron of about 1 mm becomes the adhering metal. I understood that.

Therefore, the inventor examined the furnace height Hi and the furnace port inner diameter R of the furnace body at which the spitting granular iron having a particle size of about 1 mm does not adhere to the furnace port. Specifically, as shown in FIG. 3, the inner diameter R of the furnace port is taken on the horizontal axis, the height Hi in the furnace is taken on the vertical axis, and each of the furnace heights in which spitting granular iron having a particle diameter of 1 mm does not adhere to the furnace mouth. The height Hi and the furnace port inner diameter R were calculated by a plurality of experiments and physical calculations and plotted in FIG.
As shown in FIG. 7, the physical calculation is based on the speed v of spitting granular iron in a state where oxygen is blown into the furnace body, and the velocity V of the updraft (CO gas) generated when oxygen is blown. Focusing on (superficial velocity), drag, and gravity, we use these to establish an equation of motion in which spitting granular iron does not adhere to the furnace port and solve it. In addition, spitting grain iron was made spherical.

As shown in FIG. 3, for example, when the lance feed rate is 700 Nm ³ / min, the furnace height Hi and the furnace port inner diameter R at which the spitting particle iron having a particle size of 1 mm does not adhere to the furnace port are , Line K1 (hereinafter referred to as non-attached line K1). In this case, it was found that by determining the furnace height Hi and the furnace port inner diameter R so as to be on the non-attachment line K1, it is possible to configure a furnace body in which spitting granular iron is difficult to adhere.
Here, the inner diameter R of the furnace port can be indicated by the inner diameter D of the straight body of the furnace body, and the furnace height Hi can also be indicated by the furnace body height H. Considering the relationship between the furnace body height H and the furnace body straight body inner diameter D, R is replaced with the furnace body straight body inner diameter D and the furnace height Hi is replaced with the furnace body height H.

When the furnace body height H and the furnace body straight body inner diameter D are determined by the line K1, furnace bodies having various internal volumes can be configured. Therefore, the inventor drawn a constant furnace volume line V1 having a constant furnace volume in FIG. 3, and obtained a contact point P1 between the constant furnace volume line V1 and the non-attached line k1.
When the relationship between the furnace port inner diameter R (furnace body barrel inner diameter D) and the furnace height Hi (furnace body height H) is point P1, the most spitting granulated iron in the furnace body with a constant furnace volume. It turns out that it becomes a furnace body which is hard to adhere.

Here, when the vicinity of the point P1 is seen, the non-adhered line K1 and the constant furnace volume line V1 are close or overlapped with each other, and the adjacent point between the non-adhered line K1 and the constant furnace volume line V In P2 and P3, the same effect as the point P1 can be obtained.
Therefore, it is preferable to determine the furnace port inner diameter R and the furnace height Hi within the range of points P2 to P3 in the non-attached line K1.
In the same manner as described above, a plurality of adjacent points between a plurality of non-adhered lines and a plurality of constant-in-furnace volume lines are obtained in consideration of operating conditions, and an approximate curve for these adjacent points is obtained, as shown in FIG. Thus, the curves L1 and L2 were obtained.

When an approximate expression of this curve is obtained, the curve L1 is 2.2624ln (R) +6.2856, and the curve L2 is 2.2624ln (R) +4.4642.
Accordingly, when the relationship between the furnace height Hi and the furnace port inner diameter R is in the region (optimal region) surrounded by the curves L1 and L2, that is, if the equation (1) is satisfied, the attached metal The deposition rate (growth rate) can be reduced.
The furnace volume of the furnace body is preferably determined in accordance with the amount of hot metal that is actually operated, that is, the total amount W of main raw materials to be put into the furnace body. For example, if the furnace body is too small with respect to the total amount W of the main raw materials to be put into the furnace body, the adherence metal tends to adhere to the furnace port, and if the furnace body is too large with respect to the total amount, the heat dissipation loss increases. . Therefore, various experiments were conducted on the relation between the growth rate of the adhering metal and the heat dissipation loss, the small inner diameter R of the furnace port, and the height Hi in the furnace with respect to the total amount W of the hot metal main material to be put into the furnace. And by simulation and physical calculation. According to this, when the inner diameter R of the furnace port and the height Hi in the furnace satisfy W / 2.25R ² ≦ Hi ≦ W / 1.50R ² with respect to the total amount W of the main raw material, the adhesion metal It was found that the heat dissipation loss can be reduced with the slow growth rate of.

Now, normally, when the molten steel (hot metal) in the furnace body is discharged from the furnace body (tapping water), the furnace body is tilted toward the outgoing steel side and is discharged from the outlet port (outlet opening) of the furnace body. When slag comes out from the furnace opening when the molten steel is discharged, the amount of slag in the molten steel pan that receives the molten steel increases and the quality of the molten steel deteriorates.In addition, the slag that has flowed out of the furnace opening does not enter the molten steel ladle. It is necessary to prevent the slag from coming out of the furnace port because there is a risk of burning the steel receiving cart.
When the molten steel is discharged, that is, when the furnace body is tilted toward the steel outlet side, the furnace holding volume Vi that prevents the slag from exiting from the furnace port and the total amount W of the main raw material of the molten steel to be put into the furnace body Various experiments, simulations, and physical calculations were used for experiments. When these relationships are Vi / (W × 0.94 / 6.9) ≧ 0.35, slag did not come out from the furnace port during steel output, and the steel output work could be performed smoothly. . Note that “0.94” in the above formula represents the yield coefficient (%) in the decarburization process, and “0.69” in the above formula represents the specific gravity of the hot metal (main raw material). Is.

  According to this invention, it becomes difficult for spitting granular iron used as adhesion metal to adhere to a furnace mouth.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The furnace body of the converter in the method for adjusting the profile of the furnace body of the present invention will be described. As shown in FIG. 1, the converter of the present invention is an upper-bottom blown converter in which oxygen can be supplied from the upper side of the converter and gas can be blown from the bottom of the converter. Hot metal (molten steel), scrap, etc. can be accommodated.
The furnace body 1 is composed of an iron skin 2 formed in a cylindrical shape with a bottom, and a plurality of refractories 3 (for example, refractory bricks) provided inside the iron shell 2. A bottom blowing tuyere 5 for blowing gas is provided at the bottom 4 of the furnace body 1, and a furnace mouth 6 is formed on the side facing the bottom blowing tuyere 5 (bottom 4 of the furnace body). An upper blowing lance 7 for blowing oxygen or the like into the furnace port 6 can be inserted.

The iron skin 2 has a bottom portion 10, an enlarged portion 11 whose inner diameter and outer diameter gradually increase from the bottom portion 10 toward the furnace port 6, and a continuous inner diameter and outer diameter from the enlarged portion 11. It has a constant straight body 12 and a throttle part 13 whose inner and outer diameters gradually decrease from the straight body 12 toward the furnace port 6 side.
The refractory 3 is affixed in order in the iron shell 2 along the bottom part 10, the enlarged part 11, the straight body part 12, and the throttle part 13 of the iron skin 2, and the inner surface of the affixed refractory 3 is It is substantially along the inner surface of the iron skin 2. A hot water outlet 9 (outgoing steel outlet) is formed in the straight body portion 12 of the iron skin 2 for hot metal 8 (molten steel).

From the above, the furnace body 1 is formed with the furnace shell 15 and the refractory 3 so as to form the furnace expansion portion 15 whose outer diameter or inner diameter gradually increases, and is formed continuously from the furnace expansion portion 15. Alternatively, a furnace straight body portion 16 having a substantially constant inner diameter and a furnace throttle portion 17 having an outer diameter or an inner diameter that decreases from the furnace straight body portion 16 toward the furnace port 6 are formed.
Next, a method for adjusting the profile of the furnace body will be described.
In the profile adjusting method of the present invention, when the main raw material is charged into the furnace body 1 of the converter having an upper bottom blowing function, the inner wall contour of the furnace body 1 is satisfied so as to satisfy the expressions (1) to (3). The shape is adjusted.

  In the formulas (1) to (3), the furnace height Hi is the distance from the furnace port 6 to the molten metal surface when the main raw material is charged into the furnace body 1. The inner diameter R of the furnace port is the inner diameter of the refractory 3 provided at the outermost end of the furnace restricting portion 17 (the restricting portion 13 of the iron shell 2). It is the distance to the inner surface of the refractory 3b. The in-furnace holding volume Vi is a volume in which the furnace body 1 can hold molten steel when the furnace body 1 is tilted by 90 ° toward the steel output side. The furnace volume Vo is the total volume in the furnace (the volume surrounded by the refractory 3). The total amount W of the main raw material is a scheduled amount per charge performed after completing the profile adjustment, and is determined based on the next refining schedule when the profile is adjusted.

Next, a specific example of the profile adjustment method will be described.
The inner wall contour shape of the furnace body 1 is preferably adjusted by changing the thickness of the refractory 3 provided in the furnace body 1. For example, when profile adjustment is performed on an existing furnace body 1, profile adjustment may be performed when the furnace body 1 is repaired or repaired. Assuming that the main raw material is charged into the furnace body 1 when repairing or repairing the furnace body 1, the thickness T1 of the refractory 3 is changed so as to satisfy the expressions (1) to (3). . By changing the thickness T1 of the refractory 3, the thickness T of the furnace body 1 changes. As shown in FIG. 1, the thickness T <b> 1 of the refractory 3 is a distance from the facing portion facing the inner surface of the iron skin 2 to the inside of the diameter.

The repair of the furnace body 1 is a repair for simply improving the life of the furnace body 1, and in the steelmaking factory, the refractory 3 attached to the furnace body 1 is repaired for every 10 charges. This is done by spraying refractories. When repairing the furnace body 1, assuming that the main raw material is charged in the furnace body 1 to be repaired, the furnace body 16 and the furnace throttle are satisfied so as to satisfy the expressions (1) to (3). The inner wall contour shape is adjusted by changing the thickness T1 of each refractory 3 by spraying a refractory for repair to the refractory 3 attached to the part 17 and the furnace expansion part 15.
The furnace repair of the furnace body 1 is for the purpose of renewing the furnace body 1 that has reached the end of its life due to the loss of the function of the furnace body 1 due to further erosion of the refractory 3 and the deterioration of the refractory itself. Is to be done. In a steelmaking factory, for example, by replacing the refractory 3 in the furnace body 1 with the temperature of the furnace body 1 lowered to room temperature and stopping the operation of the converter about every 5000 charges or about every 150 days. Do. When the furnace body 1 is repaired, a new refractory 3 is attached to the furnace body 16, the furnace throttle part 17, and the furnace expansion part 15 so as to satisfy the expressions (1) to (3). Thus, the thickness T of each part of the furnace body 1 is changed to adjust the inner wall contour shape.

In the above, the profile adjustment is performed in accordance with the repair of the furnace body 1 or the furnace repair, but the present invention is not limited to this. For example, if the amount to be refined (the total amount W of main raw materials to be put into the furnace body 1) is scheduled to change significantly, the total amount W of the main raw materials is changed before the total amount W of main raw materials changes significantly. The profile adjustment of the furnace body 1 may be performed in consideration.
Moreover, it is applicable also when manufacturing the furnace body 1 newly in a steelmaking factory (installing a furnace body newly). In this case, assuming that the main raw material is charged into the newly established furnace body 1, the thickness T1 and the number of refractories 3 to be attached to the iron shell 2 and the direction of attachment are attached so as to satisfy the expressions (1) to (3). Considering this, the inner wall contour shape is adjusted.

The above equation (2) was examined by various experiments, simulations, and physical calculations. FIG. 4 summarizes the experimental results. FIG. 3 is obtained by subtracting curves L3 and L4 having a constant charging amount according to the total amount W of the main raw material. As can be seen from FIG. 4, the boundary region surrounded by the curves L1 to L4 is the most preferable region, and the relationship between the furnace height Hi and the furnace port inner diameter R according to the total amount W of the main raw material is W / 2. It was found that by setting 25R ² ≦ Hi ≦ W / 1.50R ² , the growth rate of the adhered metal is slow and the heat dissipation loss can be reduced.
The expression (3) is obtained by various experiments and is obtained from the result of performing a plurality of decarburization processes while changing the in-furnace holding volume Vi and the total amount W of the main raw material in an experimental furnace or the like. .

FIG. 5 summarizes the experimental results, and “W × 0.94 / 6.9” in Equation (3) indicates the volume of the molten steel to be produced (hereinafter referred to as the output steel volume). As can be seen from FIG. 5, when the steel output ratio obtained by dividing the in-furnace holding volume Vi by the steel output volume is less than 0.35, the slag S flows out of the furnace port 6 during the steel output, and the effect is generated. The steel time takes 6 minutes or more, and when the steel output ratio is 0.35 or more, the slag S does not flow out of the furnace port 6 and the steel output time can be made within 6 minutes for most charges. .
In addition, in the above, it is preferable to set the steel output ratio to 0.35 or more, that is, Vi / (W × 0.94 / 6.9) ≧ 0.35. However, the slag S is formed on the molten metal surface in the same manner as the decarburization process in the dephosphorization process.

Therefore, since it is necessary to prevent the slag S from coming out of the furnace port 6 even in the hot water after the dephosphorization treatment, the relationship of Vi / (W × 0.94 / 6.9) ≧ 0.35 Is not limited to the decarburization treatment, and it is preferable to set the outgoing steel ratio (the outgoing hot water ratio) to 0.35 or more when performing the dephosphorization treatment and discharging the molten iron. In other words, Vi / (W × 0.94 / 6.9) ≧ 0.35 can be applied to either dephosphorization or decarburization.
FIG. 6 summarizes the results of operation with the shape of the furnace body changed (profile adjustment). In Examples 1 to 4 of FIG. 6, the profile of the furnace body 1 is adjusted so as to satisfy all of the expressions (1) to (3) while changing the total amount W of the main raw material, and the dephosphorization process is performed with dephosphorization. The charcoal treatment was performed. In Comparative Examples 1 to 15, the profile of the furnace body 1 was adjusted so that at least one of the formulas (1) to (3) was not satisfied, and the decarburization treatment was performed with the dephosphorization treatment. Went.

In the examples and comparative examples, the [P] concentration of the hot metal charged into the converter is 0.030 to 0.040%, which is higher than the upper limit of 0.020% of the P standard, The dephosphorization treatment was performed under the necessary conditions. Further, the lance for blowing oxygen has 6 holes, its hole diameter is 42 mm, the acid delivery angle is 15 °, the oxygen delivery speed for delivering oxygen is 3.0 Nm ³ / min · t, and the lance height is 2. The operating conditions of each experimental example and comparative example were the same, with 8 m (height from the hot water surface to the tip of the lance) and the flow rate (velocity) of the bottom blowing gas set to 0.06 Nm ³ / min · t.
In each of the examples and comparative examples, the amount of dust generated per ton of molten steel (kg / t), the interval of collecting the metal (ch / time), that is, from the completion of the removal of the adhering metal to the start of the removal operation again Total number of charges that can be operated, heat dissipation loss (Mcal / t), refractory basic unit (kg / t) indicating the amount of refractory 3 melted by melting per ton of molten steel, steel output time (min / ch), etc. I investigated.

As shown in FIG. 6, when the example of the present invention and the comparative example in the case where the total amount W of the main raw material is the same, in the example satisfying the formulas (1) to (3), a good operational result is obtained. Obtained.
For example, comparing Example 2 in which the total amount W of the main raw material is 200 t / ch and Comparative Examples 3 to 6, in Example 2, the bullion collecting interval is 20 ch / time, which is larger than Comparative Examples 3, 5, and 6. In Example 2, the amount of dust generated is 14 kg / t, which is less than those in Comparative Examples 3, 5, and 6. Moreover, the heat dissipation loss in Example 2 was 10 Mcal / t, which was less than that in Comparative Example 4, and the steel output time was within 6 minutes.
Therefore, the operation suitable for the total amount W of the main raw material can be performed by adjusting the thickness of the furnace body 1 so as to satisfy the expressions (1) to (3) according to the total amount W of the main raw material. Became.

  The furnace body profile adjustment method of the present invention is not limited to the above-described embodiment. In other words, in the above embodiment, the inner wall contour shape is adjusted mainly by changing the thickness T1 of the refractory 3. However, the number of refractories 3 to be affixed to the iron shell 2 and the affixing direction are changed. Alternatively, the inner wall contour shape may be adjusted by changing the shape of the refractory 3 (refractory brick) to be attached to the iron skin 2 or the like. In the above-described embodiment, the thickness T1 of the refractory 3 is changed by spraying a refractory for repair on the refractory 3. However, as a matter of course, the refractory 3 is scraped off. The thickness T1 may be changed.

  Moreover, the furnace body to which the profile adjusting method of the present invention is applied is not limited. That is, the present invention can be applied to a dephosphorization furnace for performing a dephosphorization process and a decarburization furnace for performing a decarburization process, and can be applied to all converter bodies that operate.

It is a whole side view of the furnace body of a converter. It is a whole side view when a furnace body is inclined 90 degrees. It is a figure which shows the relationship between a furnace port internal diameter and furnace height. It is the figure which showed the optimal area | region in case the total amount of a main raw material is 200 t / ch in the related figure of a furnace port internal diameter and furnace height. It is the figure which plotted the relationship between the steel output ratio and the steel output time. Examples and comparative examples are summarized. It is a model figure in the flight state of spitting granular iron at the time of blowing oxygen.

Explanation of symbols

1 Furnace 2 Iron skin 3 Refractory (Refractory brick)

Claims (2)

When the main raw material of 80 to 250 tons is charged into the furnace body of the converter having the top bottom blowing function, the inner wall contour shape of the furnace body is adjusted so as to satisfy the expressions (1) to (3). A furnace body profile adjustment method.

  2. The furnace body profile adjustment method according to claim 1, wherein the inner wall contour shape of the furnace body is adjusted by changing a thickness of a refractory provided in the furnace body.

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