KR20020050351A - Method for reducing the circumferential flow of furnace bottom - Google Patents

Abstract

PURPOSE: A method for reducing annular flow of hearth bottom for a blast furnace is provided which extends a life cycle of refractory materials by blocking the annular flow of hot metal generated in the blast furnace process, thereby preventing erosion of the refractory material of the hearth bottom. CONSTITUTION: In a method for reducing annular flow of hearth bottom for a blast furnace in which the hot metal is discharged into a continuous casting line through tap holes(120) after iron ore charged into the blast furnace along refractory materials(130) of hearth bottom constructed on the inner wall of the hearth bottom of a blast furnace is reacted with air flown in through tuyeres(110) to be melted into hot metal, the method is characterized in that generation of coke free space(CFS) is intercepted by reducing a blowing amount of the tuyeres(110) from a regulation value to a level of 65 to 75% of the regulation value, thereby increasing a tap hole depth(C) and maintaining a hot metal level of the blast furnace(100) to an elevation which is 0.8 m or less on the basis of the tap holes(120) in case that an annular flow of the hot metal is generated at the bottom part of the blast furnace(100) resulting in erosion of the refractory materials(130) of the hearth bottom.

Description

Reduction method for blast furnaces {Method for reducing the circumferential flow of furnace bottom}

The present invention relates to the furnace refractory to which the molten iron is in direct contact with the molten iron during the operation of the blast furnace, in particular to prevent the erosion of the furnace refractory by blocking the cyclic flow of the molten iron generated in the blast furnace operation process can extend the life of the furnace refractory. The present invention relates to a method for reducing blast furnace furnace reflux.

In general, a blast furnace is a device that melts iron ore using molten refractory built along its inner wall to produce molten iron. In this blast furnace operation, furnace refractory is eroded physically or chemically due to mechanical friction due to the flow of molten iron. You will get a lot of damage easily.

Therefore, when the residual thickness of the blast furnace refractory wears down to the allowable value, the number of refractory is made. In order to extend the life of the blast furnace, it is very important to suppress the erosion of the furnace refractory.

For example, as a method of suppressing the erosion of the furnace refractory structure built into the blast furnace, Japanese Patent Laid-Open Publication No. Hei 9-78112 has proposed a method of injecting a lump ore containing TiO 2 into the charge of the blast furnace. This method has been implemented to increase the viscosity of molten iron and to reduce the friction of mechanically applied to the furnace refractory and to form a layer of Ti (C, N) on the furnace.

However, Japanese Patent Publication discloses that it is not possible to selectively load lump ore when local erosion site is generated in blast furnace furnace refractory, and because it takes time for the lump ore to fall from the top to the bottom, There was a problem that it takes a long time to obtain the effect of the protection.

In addition, it is known that the amount of lump ore is required in a large amount, so that the associated costs such as the increase in the cost of the molten iron are increased, as well as the fluidity of the furnace melt is seriously affected in the drawing work.

On the other hand, as another method of suppressing the erosion of the furnace refractory built into the blast furnace, according to Japanese Patent Laid-Open Publication No. Hei 9-298572, the depth of the exit port forming the lower side of the blast furnace is increased by using the mud material, A method of suppressing the annular flow generated in the flow process has been proposed.

However, the Japanese Patent Laid-Open Publication not only increases additional costs due to the development of mud materials, but also includes many factors that greatly affect the depth of the exit port in addition to mud materials in the actual operation process. There was a problem that the method of suppressing the erosion of the refractory is not appropriate.

In addition to the above methods, a method of extending the life by reducing the heat load of the Roger refractory has been proposed by controlling the flow rate of the flow rate of the cooling water sprayed to the furnace of the blast furnace to reduce the heat load of the Roger refractory. .

Accordingly, the present invention has been made in order to solve the problems described above, by changing the shape of the coke layer generated on the bottom of the blast furnace, and by controlling the blowing amount to minimize the mechanical frictional force applied to the furnace refractory, It is an object of the present invention to provide a method for reducing blast furnace furnace reflux, which is capable of extending the life of furnace refractory.

The present invention for achieving the above object, the cyclic flow generated from the molten iron generated from the furnace refractory by reducing the blowing amount of the tuyere to a level of 65 to 75% when the heat load is generated and eroded in the furnace refractory of the blast furnace In addition, the molten iron is maintained at a height of 0.8 m or less on the basis of the exit port, thereby preventing the generation of coke free space in which only the molten iron exists.

1 is a view showing the internal structure of the blast furnace according to the present invention,

Figure 2 is an experimental apparatus for simulating the blast furnace hearth flow according to the present invention,

3 is a view showing a coke-filled layer shape of the blast furnace core portion according to the present invention,

4 is a comparative view measuring the flow rate of the blast furnace bottom section according to the present invention,

5 is a view showing a force acting on the core coke layer according to the present invention,

6 is a view comparing the core coke layer and the slag layer according to the present invention,

Figure 7 shows the starting depth and the bottom edge aging temperature when the air flow is reduced to 70% in the blast furnace according to the present invention.

Explanation of symbols on the main parts of the drawings

100: blast furnace 110: windball

120: exit 130: refractory

C: Exit depth D: Core coke floor

Hereinafter, an embodiment according to the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIGS. 1 to 7, iron ore charged along the furnace refractory 130 built on the furnace inner wall of the blast furnace 100 reacts with the air introduced through the tuyere 110, and melts into molten iron. In providing a conventional method for reducing blast furnace bottom annular flow, which is discharged to the continuous casting line via the precursor 120, an annular flow of molten iron is generated at the bottom of the blast furnace 100, and the furnace refractory 130 is eroded. In this case, the airflow of the tuyere 110 is reduced to a level of 65 to 75% from the prescribed value to increase the depth of the exit port (C), and the molten iron level of the blast furnace 100 based on the exit port 120 on the basis of the exit port 120. Maintained at a height of 0.8m or less, it is characterized by blocking the generation of coke free space (CFS).

First, among the components of the blast furnace 100 according to the present invention, since the wind hole 110 and the outlet 120 and the furnace refractory 130 are the same as in the prior art, detailed description thereof will be omitted here, but in the present invention, It is noted that there is a characteristic in adjusting the airflow amount of the tuyere 110 and the height of the coke free space.

Example 1

1 is an internal structural diagram showing a blast furnace hearth according to the present invention, the hot air of the high temperature / high pressure flowing through the tuyere 110 generates a reducing gas while forming a cavity at the tip of the tuyere, the reducing gas is The combustion space generated is called combustion zone (A), and the horizontal distance of the combustion zone is defined as combustion zone depth (B).

In addition, the mud introduced into the blast furnace during the closing operation of the exit port 120 to block the outflow of the molten iron in the fired state in the mushroom form (mushroom), at this time the outer wall and mud filling filler (E) of the blast furnace (100) The distance from the tip of the ship is defined as the starting depth (C).

In addition, the core coke layer (D) is injured due to the buoyancy of the molten iron in the hearth portion of the blast furnace 100 is defined as a coke free space (CFS) is the coke free space (CFS), in this case Of course, the molten iron flow of the bottom part is greatly changed by the shape and size.

Therefore, if a filling layer having a shape that promotes the bottom annular flow of the molten iron melted in the blast furnace 100 is formed, the possibility of mechanical erosion of the bottom refractory becomes high, and means for suppressing the annular flow generated in the molten iron. Therefore, it is necessary to derive an operation method for inducing the shape of the core.

2 is an experimental apparatus for simulating the blast furnace hearth flow according to the present invention, the molten iron flow in the blast furnace 100 was simulated with water, the equation (1) as a means for meeting the conditions between the actual blast furnace and the water model The experiment was conducted by setting the same dimensionless Reynolds number.

[Equation 1]

Where m is the test model, p is the prototype, P is the density, V ₀ is the mean velocity in the hearth, D _T is the hearth, ε is the porosity, and C _B is 180 ( 1-ε) 2μ / ε ³ Dp ² .

Therefore, the test apparatus of Figure 2 is a device for testing with water in place of the molten iron of the blast furnace 100, the water supplied through the water supply line 10 is constantly adjusted through the water level control system 20 In Figure 2 illustrates a device that is drawn into the container 30 is discharged to the outside through the discharge port (40).

At this time, the mud filling layer 50 is formed on the circumferential surface of the discharge port 40 constituting the container 30 to a predetermined thickness, and the flow rate sensor 60 and the side wall of the container 30 measure the flow velocity. It is equipped with a thermocouple 70 for measuring the temperature.

3 is a view showing the shape of the coke-filled layer of the blast furnace core according to the present invention, Figure (a) is a state without the coke free space (CFS), Figure (b) is a coke free space (CFS) is generated It shows the state.

4 is a result of measuring the flow rate of the bottom side wall portion on the basis of FIG. 3, since the flow rate discharged to the exit port 40 is discharged with a slight up and down error at the set value, it outputs the absolute flow rate of each measuring point The relative flow rate divided by the precursor flow rate was used.

As a result of the measurement, when the coke free space (CFS) is formed, it can be seen that the flow rate is more than twice higher than without the coke free space, which means that the annular flow of the molten iron is strongly generated in the bottom wall, In the actual blast furnace, it can be seen that a method of minimizing the generation of coke free space has to be derived.

Example 2

Therefore, the expansion of the coke free space (CFS) in the furnace wall portion of the blast furnace not only accelerates the flow of the molten iron to accelerate the erosion of the furnace wall, but also the mud material filled at the exit of the blast furnace contacts the core coke layer (D), Formation of lumps (MUD MASS) is impeded, thus extending the depth of the exit.

At this time, since the depth of the exit port acts as an important factor for reducing the cyclic flow, it is important to derive an operation factor affecting the increase in the coke free space. Of course, since the coke free space is increased or decreased by buoyancy of the core coke layer (D), the work of estimating the lower position of the core coke layer is important.

5 is a view showing a force acting on the core coke layer according to the present invention, the force applied to the core coke layer is indicated by an arrow. At this time, the upward direction in the arrow is the buoyancy of the gas flowing out of the combustion zone (A) and the buoyancy of the melt, the downward direction is the gravity of the coke filling filler.

In addition, although the dynamic pressure (P) acts in a region other than the combustion zone (the central region), the combustion zone A is offset by the buoyancy of the gas flowing out of the fluctuation pressure, so the lower region of the combustion zone A is reduced. Only the weight of coke acts as a downward force.

Therefore, the lower region of the combustion zone A is a condition that is easier to form the coke free space (CFS).

In consideration of the above, the work of estimating the bottom position of the core coke layer is made possible by assuming a force balance as shown in Equation (2).

[Equation 2]

A + (H ₁ + H ₂ + H ₃ ) × ρc × g × (1-ε) = (H ₂ × ρs + H3 × ρm) × g × (1-ε)

Where H1 is the distance from the top of the slag layer to the tuyere (m)

H2: Thickness of core coke immersed in slag (m)

H3: Thickness of core coke layer submerged in molten iron (m)

ρm, ρs, ρc: Density of molten iron, slag and coke (㎏ / ㎥)

ε: porosity of core coke layer (-)

6 is a view of calculating the lower position of the core coke layer at the lower position of the combustion table based on the exit port level according to the present invention. If the calculated value is a positive value, the lower position of the core coke layer is discharged. It means higher than the pioneer level, it is negative and means that the bottom height of the core coke layer is lower than the starting level.

In addition, when the molten iron level of the blast furnace is the same as the exit port level, if the thickness of the slag layer exceeds 0.8m, the lower end of the core coke layer is higher than the exit port position. In addition, as the thickness of the slag layer increases, the lower end position of the core coke layer further rises, and the mud material inserted into the outlet port comes into contact with the core coke layer.

Therefore, rather than forming a mud mass in contact with the mud resumption core coke layer inserted into the exit port, it is more likely to be scattered in contact with the coke free space (CFS), making it difficult to secure the exit depth. It is necessary to keep the charter level low.

At this time, when looking at the composition of the force balance, the combustion zone plays a role to cancel the downward force on the core coke layer, it is necessary to keep the depth of the combustion zone short to reduce the area of the coke free space (CFS) In order to do this, a method of reducing the air volume of the exit port is required.

Figure 7 shows the starting depth and the bottom edge temperature when the air flow is reduced to 70% in the blast furnace according to the present invention, it can be seen that the starting depth (C) increases from the previous 3200mm level to more than 3500mm As a result, the temperature of the bottom wall of the furnace gradually decreases.

Therefore, as the temperature of the bottom side wall gradually decreases, it is expected that the flow of molten iron is stabilized and the generation of annular flow is reduced, and the formation of the coke free space (CFS) is reduced due to the increased depth of the ship.

This phenomenon is due to the fact that the annular flow of the molten iron is suppressed in the furnace by the combined factors such as the reduction of the coke free space (CFS) and the increase in the molten iron depth due to the decrease in temperature of the molten iron due to the increase of the molten iron. In order to suppress the heat load and erosion of the molten furnace refractory material, it can be seen that the reduction of the annular flow by the reduction of the area of the coke free space is the most effective.

As described above, according to the method for reducing the blast furnace bottom flow, the air flow in the blast furnace is controlled and the generation of coke free space is blocked, thereby extending the life of the furnace blast furnace refractory, and thus improving the furnace refractory. Additional costs will be reduced.

Claims (1)

The iron ore charged along the furnace refractory 130 constructed on the furnace inner wall of the blast furnace 100 reacts with the air introduced through the tuyere 110, melts with molten iron and passes through the outlet 120 to the continuous casting line. In providing a conventional method for reducing the bottom ring flow for blast furnaces to be discharged, When the annular flow of molten iron occurs at the bottom of the blast furnace 100, and the furnace refractory 130 is eroded, the blowing air volume of the tuyere 110 is reduced to a level of 65 to 75% from the prescribed value, thereby increasing the depth of departure port C. In addition, the molten iron level of the blast furnace 100 is maintained at a height of 0.8 m or less based on the outlet 120 to block the generation of coke free space (CFS). Reduction method.