JPH09157714A - Furnace bottom structure in blast furnace and operation of blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To take an operational action for stopping temp. rising in detecting the temp. rise tendency of the side wall part of the furnace hearth in a blast furnace and to surely and quickly allow the resulted effect to act on the temp. rising position. SOLUTION: The structure of the furnace bottom in the blast furnace having four or more of iron tapping holes, is constituted of two or more sets of the iron tapping holes having mutually different height positions, by using two or more of the iron tapping holes having the same height position as one set. In the blast furnace operation, tapping the molten iron while changing over plural iron tapping holes having the same height position by using the blast furnace having this furnace bottom structure, in the case the temp. shown with a temp. sensor 13 arranged at the sidewall peat of the furnace hearth shows the raising tendency, the iron tapping holes in the set tapping upto this time are changed over so as to tap the molten iron from the iron tapping holes in the set having the different height position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a furnace bottom structure relating to the structure of a tap hole of a blast furnace, and a method of operating a blast furnace utilizing the tap hole having the structure.

[0002]

2. Description of the Related Art In the hearth of a blast furnace, there is a coke-filled area called a core, and the voids in the coke are filled with molten iron produced by reducing or melting ore.
The molten slag has accumulated. As the hearth brick, a refractory containing carbon as a main component is usually used. The flow of the hot metal differs depending on the erosion profile of the furnace body, the shape of the solidified layer formed on the eroded surface, the shape of the lower end of the core, the liquid permeability in the core, and the like. For example, compared to when the entire furnace core is completely submerged and in contact with the furnace bottom, when the entire furnace core floats and a narrow gap is created between the furnace core and In addition, when the center of the furnace core comes into contact with the furnace bottom and the peripheral part floats and there is a gap, an annular flow is made through this gap toward the taphole. The refractory at the bottom of the hearth or the side wall of the hearth, which is located in the part where a large amount of hot metal flows, receives a large amount of heat load. On the other hand, in normal blast furnace operation, the temperature change of the refractory is monitored by a thermometer embedded in the refractory at the bottom of the hearth or the side wall of the hearth, and the temperature condition of the bottom of the hearth or the side wall of the hearth is indirectly evaluated. There is.

Thus, when the temperature of the refractory to be monitored tends to rise, it is necessary to take measures to prevent the corrosion of the refractory. As a countermeasure, for example, a method of controlling cooling from the outside as shown in Japanese Patent Laid-Open No. 3-274207, or a raw material containing Ti from tuyere as shown in Japanese Patent Laid-Open No. 3-24211. The method of blowing air, or by controlling the charge and air blowing conditions from the furnace top as shown in Japanese Patent Laid-Open No. 1-225711, the air permeability and liquid permeability of the furnace core are first changed, whereby the hot metal Methods such as changing the flow are usually taken.

[0004]

However, JP-A-3-2
As described in Japanese Patent No. 74207, in a method of controlling cooling from the outside, it is desirable to strongly cool a portion having a large amount of hot metal flow in the furnace and a large heat load, but it is strongly cooled due to facility restrictions of the cooling structure. It is difficult to finely control what should be weakened and what should be weakened. In addition, this method first promotes the formation of a hot metal solidification layer in the furnace due to the effect of cooling, and changes the hot metal flow path to protect the refractory by the formation of this solidification layer. It takes a considerable amount of time for the effects to appear.

Further, the method of introducing a raw material containing Ti from the tuyere as in JP-A-3-24211 produces a solidified product called titanium bear such as TiC or TiN in the hot metal, and the solidified product is the bottom of the furnace. Alternatively, it is intended to protect the refractory by attaching it to the refractory on the side wall of the hearth. However, most of the titanium compounds introduced from the tuyere become slag components as titanium oxide and are slag with the slag, resulting in poor yield. Also, when Ti enters the hot metal side, Ti moves along with the flow of the hot metal, so that it is difficult to generate and act the titanium bear in an intended place.

Further, as disclosed in Japanese Patent Laid-Open No. 1-225711, the ventilation and liquid permeability of the furnace core are first changed by controlling the charge from the top of the furnace and the blowing conditions, thereby changing the flow of hot metal. The method takes a great number of days for the effect to appear, and it is very difficult to concentrate the effect on a specific place to produce the effect.

In the present invention, when the temperature rise tendency of the hearth side wall is detected, an operation action is taken to stop the temperature rise, and the effect is accurately and quickly exhibited in the temperature rise region. It is an object of the present invention to provide a blast furnace bottom structure and a blast furnace operating method capable of achieving the above.

[0008]

Means for Solving the Problems The inventors of the present invention have analyzed the temperature fluctuations of the refractory material on the side wall of the hearth during the operation of the blast furnace and conducted a model experiment in a laboratory to find out that It has been found that the flow of is greatly affected by the position and shape of the lower end of the core. Generally, when the core is floating from the bottom of the furnace, the gap between the lower end of the core and the bottom of the core has less resistance than the inside of the core, so more hot metal flows through this gap. (For example, Iron and Steel 70 (1984), p. 2224). According to the knowledge of the present inventors, when the gap between the lower end of the core and the bottom of the furnace becomes large, the hot metal flows particularly much below the lower end of the core in this gap. Therefore, the hearth side wall portion corresponding to the portion directly below the lower end of the furnace core is most likely to be subjected to the heat load due to the hot metal flow. In the present invention, when it is estimated by temperature measurement that a site having a large heat load occurs in the blast furnace hearth side wall part, the position of the lower end of the furnace core is moved upward or downward to reduce the heat load of the site. To do.

That is, the gist of the present invention is as follows.
(1) In a bottom structure of a blast furnace having four or more tap holes, two or more tap holes at the same height position are set as one set, and two or more sets of tap holes at different height positions are set. In a blast furnace operation in which a blast furnace having a blast furnace bottom structure configured according to (1) and (2) and (1) has a bottom structure and the tapping is performed while switching a plurality of tapping ports at the same height, When the temperature indicated by the temperature sensor provided on the side wall shows a rising tendency, switch to tap from the tap hole of the group at a height position different from the tap hole of the group that had been tapping until then. Blast furnace operation method.

In the furnace of the blast furnace, a lump zone in which ore and coke packed layers charged alternately from the top of the blast furnace are alternately stacked, a fusion zone in which the ore is in a semi-molten state, and the ore is reduced and melted. Then, it is divided into a furnace core for dripping between the coke, and a load is applied to the furnace core portion from above. However, most of the load above the cohesive zone and part of the load below the cohesive zone are supported by the buoyancy of the hot air gas blown from the tuyere and the inner wall of the furnace. On the other hand, in the bottom of the furnace, the hot metal and slag generated by the reduction and melting of the ore are accumulated as a liquid. The core coke is in a state of being immersed in this liquid pool of hot metal and slag, and since the hot metal and molten slag have a considerably larger specific gravity than coke, they receive buoyancy from the hot metal and slag. The balance of the force applied to the core is determined by the load applied from above and the buoyancy. When the buoyancy is larger, the lower end of the core floats away from the bottom of the furnace. The buoyancy increases as the amount of hot metal and slag that accumulates on the bottom of the furnace increase, so the more the amount of pig iron and slag, the easier it is for the core to float. Further, in the radial direction, the outer peripheral portion is more likely to receive the buoyancy due to the hot air gas and the force from the inner wall than the central portion, so that the outer peripheral portion is more easily floated.

The hot metal and slag are dropped by the reduction melting of the ore and accumulated in the bottom of the furnace while being discharged from the tap hole. Therefore, hot metal and slag flows toward the tap hole at the bottom of the furnace. Since the hot metal has a higher specific gravity than the slag, it exists below the slag, and this hot metal flow exerts a heat load on the refractory material at the bottom of the hearth or the side wall of the hearth. The flow of hot metal is greatly affected by the floating and sinking conditions at the lower end of the core. The space between the lower end of the core and the bottom of the furnace, which is formed when the core floats, has a smaller liquid flow resistance than the coke filling region of the core. Therefore, as shown in FIG. 1, when the core 5 is completely submerged and is attached to the bottom of the furnace, the whole core floats up as shown in FIG. When a narrow gap is created, a large amount of hot metal flows through this gap. Further, as shown in FIG. 3, when the center of the furnace core 5 is the bottom of the furnace and the peripheral part floats and there is a gap, an annular flow is made through this gap to the tap hole 2. According to the knowledge of the present inventors, in the hearth, the most hot metal flows directly under the lower end of the furnace core among the voids between the furnace core 5 and the furnace bottom, and therefore the heat load becomes maximum. . In the figure, 1 is a blast furnace body (refractory), 3 is a blast tuyere, 4 is a raceway, 6 is a hot metal level, and 7 is a slag level.

Generally, in a conventional operation in which a plurality of tap holes at the same height position are appropriately switched and tapped, the lower end of the core tends to settle in a substantially constant region. Since the hot metal flow concentrates on the side wall of the hearth, which is directly below, and receives a large heat load, the refractory temperature at that position rises. Therefore, when this temperature rise tendency is observed, the hot metal buoyancy is increased or decreased by switching the tap hole to be used to one with a different height position to increase or decrease the amount of pig iron stored at the bottom of the furnace. Then, the position of the lower end of the furnace core is raised or lowered. As a result, the position where the hot metal flow is concentrated and receives a large heat load is moved upward or downward, and the refractory in a specific portion is prevented from being intensively eroded.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 4 shows an example of the bottom structure of a blast furnace of the present invention, which is composed of two sets of tapholes with two tapholes at the same height position as one set. A blast furnace having a bottom structure with a total of four tap holes is shown. In the figure, 8 indicates the inside of the blast furnace. That is, in this blast furnace, No. 1 tap holes 9 and 3
No. 2 taphole 11 is 3m above the bottom of the furnace when burning, and No. 2 taphole 10 and No. 4 12 are 4m above the bottom of the furnace when burning.
At the height of Also, regarding the positional relationship on the horizontal plane,
No.2, No. 3 and No. 4 tapholes are 80 around the center axis of the blast furnace with respect to No. 1 taphole, and clockwise from the top of the furnace.
It exists at a position rotated by 180 °, 180 °, and 260 °. The internal volume of this blast furnace is 4100 m ³ . On the other hand, a temperature sensor 13 is embedded in the hearth side wall refractory material of this blast furnace. The embedding positions are set at intervals of 0.8 m in the height direction, and 15 to 20 points are installed in the circumferential direction at each height. The embedding depth is set within 0.1 m from the outer skin, and within some heights, both inside 0.1 m and inside 0.2 m.

First, FIG. 5 (a) shows the operation situation described below.

In a blast furnace having a furnace bottom structure as shown in FIG. 4, an operation was performed in which the No. 1 tap hole 9 and the No. 3 tap hole 11 were switched, and about 0.5 m above the initial bottom of the furnace. The refractory temperature θ ₁ indicated by the temperature sensor embedded 0.1 m inside the iron shell on the side wall of the hearth corresponding to 1 ° C increased by 1 ° C / day on average for 1 week continuously at each position in the circumferential direction. . Therefore, we examined the cause of this and found that the peripheral part of the core in the hearth part of the furnace floated above the bottom of the furnace, and the hot metal flow was concentrated in the peripheral part of the part directly below the lower end of the core. Therefore, the method was changed to the method of tapping using the tapping holes of No. 2 and No. 4 which are located 1 m above the tapping holes of No. 1 and No. 3 ().

As a result of this change, the side wall refractory temperature θ _{1 at the} portion showing the rising tendency stopped rising after 6 days,
After 10 days, the temperature started to decline, and after 25 days, the temperature decreased to almost the same temperature as before the upward trend began and then settled down. This is because the amount of pig iron stored in the furnace is increased by switching to the operation that uses the tap hole located at a position higher than the tap hole that was being used, the buoyancy of the hot metal is increased, and the core further rises. Then, because the position of the lower end of the furnace core moved upward,
It is highly probable that the hot metal flow no longer concentrated on the periphery of the furnace where the temperature had risen.

After that, for a while, the operation was performed by switching the No. 2 tap hole 10 and No. 4 tap hole 12, but this time, the hearth side wall corresponding to about 1.3 m above the initial bottom of the furnace. The refractory temperature θ _{2 of the} part showed a rising tendency at each position in the circumferential direction. Therefore, it was judged that the cause of this was that the hot metal flow was concentrated in the peripheral area of the portion just below the lower end of the furnace core, which was levitated as before, and this time, the tap holes of No. 2 and 4 were tapped. The method was changed again to perform tapping using No. 1 taphole and No. 3 taphole located 1 m below.

As a result of this change, the side wall refractory temperature θ _{2 at the} portion showing the rising tendency stopped rising after 5 days,
After 8 days, it started to decline, and after 20 days, the temperature had dropped to about the same temperature as before it began to rise and settled down.
This is because the amount of pig iron stored in the furnace is reduced by switching to the operation that uses the tap hole that is lower than the tap hole that was being used, the buoyancy of the hot metal is reduced, and the furnace core sinks. It is considered that the position of the lower end of the furnace core moved downward, so that the flow of hot metal did not concentrate on the inner peripheral portion of the furnace where the temperature was rising.

On the other hand, a comparative example in which a blast furnace having four tapholes at the same height is operated by the conventional method without using the blast furnace having the structure shown in FIG. 5 is shown in FIG. 5 (b). Show.

When the operation was carried out by appropriately switching the tap hole, a temperature sensor embedded at 0.1 m inside the iron skin at the side wall of the hearth, which was about 0.5 m above the bottom of the furnace at one time. It rose an average 1 ° C. / day refractory temperature theta ₁ which instructs the 'is continued for 1 week at each position in the circumferential direction. Therefore, 10 kg / t-pi of iron ore containing Ti was extracted from the tuyere.
It was attempted to protect the refractory on the side wall of the hearth by injecting g and producing titanium bear (). After the Ti injection was started, the rising tendency of θ ₁ 'was no longer observed, and it took 20 days to start the decrease (). at this point,
In order to secure the quality of the hot metal, the blowing rate of the iron ore containing Ti was reduced to 6 kg / t-pig, and the blowing of Ti was stopped when the downward tendency of the temperature θ ₁ ′ continued for 15 days (). Thus, it took 60 days from the start of Ti blowing to decrease to the temperature level before θ ₁ ′ started to rise.

[0021]

According to the present invention, when the refractory temperature on the side wall of the hearth of the blast furnace tends to increase, the height position of the taphole is switched to increase or decrease the amount of pig iron stored in the furnace. As a result, it is possible to raise or lower the position of the lower end of the furnace core to prevent the hot metal flow from concentrating at a specific height position immediately below the lower end of the furnace core, and to prevent corrosion of the refractory at that position. This method can control the hot metal flow more directly as compared with the various conventional methods, and therefore the effect appears earlier. Therefore, in the conventional method, it takes a long time from when the temperature rise of the refractory is detected and the countermeasure is started to when the effect is obtained,
Although refractory erosion may progress during this time, the present invention can prevent the progress of such erosion, and as a result, the life of the blast furnace can be extended and the facility cost can be reduced. .

In addition, when attempting to protect refractories by the conventional method, the above-mentioned cooling control method increases the heat loss and increases the fuel ratio. Similarly, the Ti blowing method changes the composition of the hot metal. Then, the hot metal quality is deteriorated, and according to the control method of the charging material or the blast, the productivity may be decreased, and a negative effect may appear as a side effect of the control, but in the method of the present invention, these operating conditions are used. There is no need to change the
No reduction in productivity.

Therefore, according to the present invention, it is possible to take an operation action against the temperature rise of the blast furnace hearth while securing the productivity and the hot metal quality of the blast furnace, and as a result, the life of the blast furnace can be extended. The effect of reducing the equipment cost can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view of a hearth of a blast furnace showing a case where a furnace core is submerged.

FIG. 2 is a schematic view of the hearth of the blast furnace, showing a case where the entire furnace core is floating.

FIG. 3 is a schematic diagram of the hearth of the blast furnace, showing a case where only the periphery of the furnace core is floating.

FIG. 4 is a diagram showing a blast furnace bottom structure of the present invention, (a) is a plan view and (b) is a side view.

FIG. 5 (a) is a diagram showing an operation example using the present invention,
(B) is a figure which shows the operation example by the conventional method.

[Explanation of symbols]

 1 ... Blast Furnace Furnace Body (Refractory) 2 ... Tap Mouth 3 ... Blow Tuyere 4 ... Raceway 5 ... Furnace Core 6 ... Hot Metal Level 7 ... Slag Level 8 ... Blast Furnace 9 ... No. 1 Tap Hole 10 ... 2 No. 1 tap hole 11 ... No. 3 tap hole 12 ... No. 4 tap hole 13 ... Temperature sensor

Claims (2)

[Claims] 1. In a furnace bottom structure of a blast furnace having four or more tap holes, two or more tap holes at the same height position are provided.
A blast furnace bottom structure composed of two or more sets of tap holes whose height positions are different from each other. 2. A temperature sensor provided on a side wall of a hearth in a blast furnace operation using the blast furnace having the hearth structure according to claim 1 for tapping while switching a plurality of tap holes at the same height. When the temperature indicated by indicates a rising tendency, the blast furnace operating method is to switch to tapping from the tapping port of the set at a height different from the tapping port of the set that had been tapping until then.