JPH09227909A - Operation of blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the wearing of a furnace hearth to the lowest limit without charging metal such as titanium for repairing the furnace hearth, into a blast furnace and to prolong the service life of a blast furnace operation. SOLUTION: Tracer is blown into the blast furnace, and when the passing time T until the tracer concn. in discharged molten iron rises since starting the blowing of the tracer is satisfied to the condition shown by the formula T>20/H (wherein, T is the passing time (min) and H is the molten iron ratio at this time (ton/day/m<3> )), the use of an iron tapping hole is limited so that the discharging quantity of the molten iron and slag becomes <=50% of that at the time of the ordinary operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention locally detects the state of hot metal flow at the bottom of a blast furnace and controls it to suppress local erosion of the bottom brick, thereby extending the operating life of the blast furnace. "Blast furnace operation method".

[0002]

2. Description of the Related Art In recent years, blast furnaces as large reactors in the ironmaking process have been gradually increasing in size as a result of pursuing improvement in production efficiency. A series of refurbishment costs such as "has also increased significantly, and extending the blast furnace operating life has led to more direct cost benefits.

Although the timing of blowing off the blast furnace is determined in consideration of the steel demand at that time or social factors such as the economy, it is basically determined by the degree of deterioration of the furnace body of the blast furnace.

The furnace body of a blast furnace is always exposed to severe conditions of high temperature and high pressure, but especially in the upper part of the furnace above the tuyere, "wear by raw material charge" is the main cause of deterioration of the furnace body. In the lower part of the furnace below the tuyere, “heat load due to high temperature hot metal flow” is considered to be the main cause of deterioration.

However, in recent years, the technique for repairing blast furnaces has improved, and it has become possible to repair the furnace body above the tuyere by taking a break for a certain period of time. However, in the lower part of the blast furnace, which is located below the tuyere, since the molten pig iron is accumulated in the molten metal pool, it is extremely difficult to repair it. It is almost impossible.

Therefore, it is no exaggeration to say that it is the life of the lower part of the furnace that determines the operating life of the blast furnace. In the lower part of the blast furnace, the part where the molten pig iron is accumulated is the hearth,
In the hearth, the refractory bricks on the hearth or the hearth wall are eroded. One of the important factors that control the erosion is the heat load due to the bottom hot metal flow.

Therefore, in order to reduce the heat load due to the hot metal flow, the titanium source is intentionally blended into the charging raw material or blown from the tuyere to intentionally produce titanium bear (TiN).
TiC is a solid solution substance that exists in the form of contacting the hearth bottom or side wall bricks and has the role of protecting bricks). .

However, in order to suppress the wear of the furnace bottom or the side wall of the hearth, introducing a titanium source into the blast furnace not only increases the cost of the titanium source but also mixes titanium in the slag, so that the slag quality is high. Worsen, causing a disadvantageous situation at the time of sale. Further, in some cases, there is a problem in that the fluidity of the hot metal is significantly deteriorated due to the generation of excess titanium bear, which causes a problem of tapping.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to more accurately understand the mechanism of the flow of bottom hot water, which is a factor of wear of refractory bricks, and to install a metal such as titanium for hearth repair in a blast furnace. Minimize furnace bottom wear without charging
The aim is to establish means that can extend the operating life of the blast furnace.

[0010]

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object. At that time, the local wear of the blast furnace is deeply affected by the "hot metal flow field" of the hearth pool. From the perspective of involvement, I investigated the flow of hot water and found that the position of the taphole, which is the source of the flow field, has an important meaning.

That is, when a simulation of the hot metal flow in the hearth of the blast furnace is performed by a mathematical model, the hot metal flow velocity is the fastest and the heat load on the furnace bottom is large because it is near the taphole for discharging the hot metal. There is a high risk of parts being worn.

Therefore, the blast furnace currently called a large blast furnace is
It has three or four tap holes at symmetrical positions with respect to its center, and by using them cyclically, that is, in order, it is possible to suppress local wear of the refractory brick near the tap hole. ing.

By the way, in the blast furnace hearth, in addition to the area filled with coke (hereinafter referred to as a coke packed bed), there is no coke in the "area occupied only by the hot metal" (hereinafter referred to as "coke-free layer"). It is clear from the blast furnace dismantling investigation that this coke packed bed is present, and the coke packed bed is displaced vertically due to the balance with “buoyancy due to hot metal and molten slag” and “load from above”. I also know what to do.

Since the liquid permeability of the hot metal is greatly different in the two types of regions, that is, the coke-filled layer and the coke-free layer, it is considered that the distribution state thereof governs the hot metal flow field. Then, when the hot metal flow field in the hearth hot water pool was evaluated by a mathematical model, the position of the taphole had a great influence on the hot metal flow field, and especially the tip of the taphole inside the furnace was coke. It was found that the hot metal flow field near the taphole changes greatly depending on whether it is located in the packed bed or in the coke-free bed.

FIG. 1 is a schematic view showing the characteristics of the furnace bottom cross section and the hot metal flow field when the taphole 10 is located in the coke packed bed 12, and as shown in FIG. 10 When the tip is located in the coke packed layer 12, it means that the hot metal extruded from the tap hole 10 (the arrow shows the flow direction) is mainly supplied from the coke packed layer 12, and the coke free layer.
Not supplied much from 14th. Therefore, the flow rate of the hot metal moving in the coke-free layer is slow, and it is in a desirable state in which the wear of the furnace bottom brick does not easily progress.

On the contrary, when the tip of the taphole 10 is located in the coke-free layer 14 as shown in FIG. 2, the hot metal extruded from the taphole 10 (the arrow indicates its flow direction) is mainly Coke-free bed is supplied from inside the coke-free bed 14
Not supplied much from 12th. Therefore, the flow velocity of the hot metal moving in the coke-free layer 14 is high, and the wear of the furnace bottom brick is likely to proceed in an undesired state.

Therefore, using the above mathematical model, trial calculations were made for the discharge time and the concentration change when the tracer was blown from the tuyere just above the taphole for each of the states shown in FIG. 1 and FIG. Figure 3 for time and concentration changes
It turns out that there is a clear difference as shown in. Here, the "discharge time" is the shortest time from the injection of the tracer from the tuyere to the maximum tracer concentration at the taphole (mi.
n).

That is, in the case of FIG. 1, since the hot metal extruded from the tap hole is mainly supplied from the upper coke packed layer, the tracer discharge time is relatively short, and conversely, FIG.
In this case, since the hot metal is mainly supplied from the lower coke-free layer, the tracer discharge time is relatively long. Therefore, it is possible to detect that "the vicinity of a taphole is in a state where there is a high risk of wear of refractory bricks" by the above method.

Next, as an effective means for suppressing the wear of the furnace bottom brick, it is conceivable to limit the use of tap holes. That is, since the cause of wear of the refractory bricks is the heat load due to the hot metal flow in the bottom of the furnace, the vicinity of the taphole is the part where the hot metal flow velocity is the fastest and the risk of wear is large. Therefore, by reducing the frequency of use of one taphole and opening the tapping interval, that is, by lengthening the time until the next taphole, the hot metal flowability near the taphole is reduced, and furnace bottom fire resistance The progress of brick wear is minimized.

Further, in a portion of the hot water pool where the hot metal hardly flows, the amount of heat supplied by the newly generated hot metal and dropping is small, so that the hot metal temperature is lowered. In particular, when the hot metal temperature falls below the solidification temperature of 1150 ° C, the hot metal solidifies,
The solidified layer of the hot metal thus generated serves to cover and protect the refractory brick, and the life of the refractory brick can be extended.

According to the present invention, the tuyere immediately above the taphole during tapping or the tuyere closest to the taphole,
Along with hot air, a tracer is blown into the blast furnace, and the time course of the concentration of the tracer in the hot metal discharged from the tap hole to the outside of the furnace is tracked, and the tracer is discharged from the start of the hot metal discharge of the tracer. When the elapsed time T until the concentration rises is detected and the elapsed time T complies with the condition shown by the following formula (1), the use of the taphole is to determine the amount of molten pig iron and slag discharged from the taphole. This is a blast furnace operation method characterized by limiting the content to 50% or less of that during normal operation.

[0022]

[Equation 1]

[However, T: elapsed time (min), H: tap ratio at that time (ton / day / m ³ )] Here, the above tracer is charged into the blast furnace as it is,
There is no particular limitation as long as it is a component that is easily reduced and dissolves in the hot metal, but it does not have a bad influence on the quality of the hot metal, etc., and acts as a tracer clearly separated from the components of general hot metal. It is preferable that the metal element satisfy the above condition. Under normal conditions, tracers used are, for example, Co, Ni, Ti and also the oxides which are easily reduced to them. In the present specification, tracer metals including such oxides may also be referred to as tracer metals.

Therefore, in a preferred embodiment of the present invention, Co is used as a tracer metal together with hot air from a tuyere immediately above the taphole during tapping or a tuyere closest to the taphole. A powder containing at least one selected from the group consisting of Ni, Ti and oxides of these metals was blown into the blast furnace and the concentration of the tracer metal in the hot metal discharged from the tap hole to the outside of the furnace was measured. While tracking the temporal change, the elapsed time T from the start of the blowing of the powder to the increase in the concentration of the tracer metal in the discharged hot metal is detected, and this elapsed time T follows the condition shown by the above formula (1). Occasionally, the use of the taphole is restricted so that the amount of molten pig iron and slag discharged from the taphole is 50% or less of the normal operation, and when the above formula (1) is not satisfied, the operation is continued as it is. Characterized by continuing It is a method of operating a blast furnace that can extend the life of the blast furnace. From another aspect, the present invention can be said to be a method of determining whether the in-furnace hot metal supply is from the coke layer or the coke free layer by the above formula (1).

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the reason why the operating conditions of the blast furnace are limited as described above in the present invention will be explained together with its operation. First, the reason for setting the tuyere into which the tracer is blown is "the tuyere just above the taphole during tapping or the tuyere closest to the taphole".

That is, whether the tip of the taphole inside the furnace is in the coke-filled layer or in the coke-free layer has a great influence on the molten metal flow around the taphole as described above. Exert. And, the influence has the most direct influence on the response time of the tracer when it is blown from the taphole which is the closest to the taphole. Therefore, the tuyere was blown into the tuyere to correctly evaluate the condition inside the furnace. The timing of blowing the tracer is
Even when the temperature change is detected by the temperature provided in the vicinity of the tap hole, it may be performed periodically after a certain time has passed.

Next, in the preferred embodiment of the present invention, Co, Ni, Ti or their oxides are used as the tracer metal blown from the tuyere for the following reasons. This is because these tracer metals are stably present in the hot metal, and usually have a low concentration in the hot metal, so that changes in the concentration can be easily detected. In addition, Co, Ni, Ti
Since the above metal is easily reduced in the hot metal, the role as a tracer is achieved even in the oxide state.

The amount of tracer added and the concentration in the hot metal are, as already mentioned, the purpose of adding the tracer is to determine whether the hot metal supply to the taphole is through the coke layer or the coke free layer. Therefore, although there is no limitation in that regard, for example, in the case of Ti, it may be blown from the tuyere for repairing the hearth, but it is distinguished from them by the amount added. It is sufficient to add the trace metal in the unit of kg and the concentration in the hot metal is 100 ppm at most. On the other hand, for repairing the hearth, it is usually charged in tons and the concentration in the hot metal is 0.2
It is clearly distinguished that it may be ~ 0.3%.

The increase in the concentration in the hot metal is defined as the start time of the increase in the concentration in the hot metal when the tracer is first detected. Next, as an index to implement restrictions on the use of tap iron,
The reason for introducing the above equation (1) will be explained.

That is, the above equation serves as a criterion for determining whether the tip of the taphole inside the furnace is present in the coke packed bed or in the coke free bed. In other words, in the above equation, if the time T from the start of blowing the tracer to the increase in the concentration of the tracer metal in the discharged hot metal is greater than “20 / H”, the hot metal extruded from the tap hole is mainly Since it is supplied from the bottom of the coke-free layer, the bottom brick is liable to wear, so it is necessary to limit the use of the tap hole and suppress the brick wear in that part.

The elapsed time T is inversely proportional to the hot metal ratio H because the flow rate of the hot metal is proportional to the amount of hot metal (that is, the hot metal ratio), and the elapsed time T is inversely proportional to the hot metal flow rate. This is because

The coefficient 20 in the above formula (1) is a proportional constant derived from numerical calculation by a numerical model, and is a numerical value that has been confirmed by various studies to be in good agreement with the actual value.

For example, FIG. 4 shows the result of numerical calculation for a blast furnace having a hearth diameter of 15.0 m and an inner volume of 5050 m ³ using a mathematical model capable of simulating the hot metal flow in the blast furnace hearth.
6 to FIG.

The above calculation is performed for each case shown in Table 1.
A steady-state solution for the hot metal flow field in the hearth is obtained, and then a tracer (here, Co) is blown into the tuyere directly above the taphole to calculate the temporal change in the tracer concentration in the tapped hot metal. I went by the procedure.

[0035]

[Table 1]

From the above calculation results, the elapsed times T in Case 2, Case 4, and Case 6 in Table 1 all satisfy the above expression "T> 20 / H", while Case 1, Case 3, and It can be seen that none of the elapsed time T in case 5 satisfies the above equation.

Therefore, from these results, in light of the relationship with FIGS. 1, 2 and 3, the proportional constant in the above equation is 20.
Was confirmed to be appropriate. Next, in order to suppress the wear of refractory bricks, the use of tap holes that are perceived as dangerous is restricted, but the amount of hot metal and slag discharged is limited to 50% of normal operation.
The reason for limiting the percentage to below is as follows.

The term "50%" means that the number of times of use of the tap iron to be noticed is reduced on the basis of the discharge amount of hot metal and slag during normal operation, and the discharge amount is 50% per day, for example. The following is to be done.

First, from the viewpoint that the main factor that greatly affects the brick wear is the heat load due to the hot metal flow in the bottom of the furnace,
In order to suppress the wear, it is only necessary to reduce the hot metal flow rate. Since the hot metal flow rate is proportional to the tap ratio as described above, the calculation for lowering the tap ratio was performed using the above mathematical model. Since the hot metal flow velocity cannot be measured directly, the heat transfer coefficient (kcal / m ² · h) at the center of the furnace is treated as being proportional to the hot metal flow velocity.

When "the vicinity of a taphole is in a state where there is a high risk of wear of refractory bricks", that is, when the temperature in the vicinity of the taphole rises and as shown in FIG. 2, the tap ratio and tap ratio FIG. 7 is a graph showing the relationship between the heat load applied to the neighboring refractory bricks, that is, the heat transfer coefficient at the center of the furnace. From Fig. 7, if the tap ratio is 1.0 or less (normally 50% or less), the coefficient of heat load on the brick decreases to 40 kcal / m ³ · h or less, and the refractory brick near the tap hole It can be seen that the risk of wear is reduced.

On the other hand, restricting the use of the tap hole is equivalent to reducing the tap ratio in the sense of reducing the hot metal flow rate with respect to the heat load applied to the refractory bricks. Therefore, from the above calculation, it was decided that the use of the tap hole, which was detected as dangerous, was restricted to 50% or less of the normal operation with respect to the amount of hot metal and slag discharged.

[0042]

EXAMPLES Next, the working effects of the present invention will be described more concretely by way of examples. (Example 1) In this example, the hearth diameter is 15.0 m and the furnace volume is 50
An operation test was carried out at 50 m ³ in a blast furnace shown in FIG. 8 having four tap holes of 1TH, 2TH, 3TH and 4TH. The blast furnace had thermometers on the side wall and bottom of the hearth as shown in FIG.

During operation at a tap ratio of 1.8, the indicated temperatures of both thermometers on the tap side of 3TH increased by 18 ° C and 15 ° C, respectively.
Therefore, 20 kg of Co ₃ O ₄ mixed with pulverized coal from the tuyere directly above this taphole is blown with hot air for 20 minutes as a tracer during tapping from the tap hole of 3TH, while the hot metal being tapped. The tracer concentration inside was measured.

The measuring method was to sample the hot metal every 5 minutes, dissolve it with an acid, and then measure the Co concentration by the atomic absorption method. The result is shown in FIG. Based on the above results, the elapsed time T from the start of the tracer metal injection to the rise in the Co concentration in the discharged hot metal is "15 <T≤20.
(Minutes) ”is satisfied and expression (1) is satisfied, so 3TH
The use of the taphole was limited to 25% of normal. After 30 hours, it was determined that the thermometer on the tap side of 3TH had recovered to the temperature before rising, and the risk of brick bottom wear was gone.

(Example 2) In the same blast furnace as in Example 1, during the operation at a tap ratio of 1.9, the indicated temperatures of both thermometers on the tap side of 1TH increased by 16 ° C and 14 ° C, respectively.

Then, a test was carried out in the same manner as in Example 1 by injecting a tracer into the furnace and determining whether or not the bottom brick had a risk of wear. Is in a high risk state. ” However, since the repair work of the gutter was carried out at another taphole, 1
The use of TH taphole could not be extremely limited, and the operation was continued with the use of TH taphole limited to 60%. Then
After 24 hours, it was judged that both the bottom temperature of the taphole at 1 TH and the temperature of the side wall of the hearth had begun to rise further, and there was a risk of wear of the bottom brick.

Therefore, when the use of the 1TH tap hole was further restricted, and the operation was performed by lowering it to 30% of the normal level, after 30 hours, the furnace bottom temperature and hearth side wall temperature recovered to the original temperature, It was determined that the risk of bottom brick wear was gone.

(Example 3) During operation at the tap ratio of 2.1 using the same blast furnace as in Examples 1 and 2, the temperature of two thermometers on the side of the tap hole of 2TH began to rise suddenly and reached 7 ° C. Rose.
Therefore, as in Examples 1 and 2, Co ₃ O _{4 is used} as a tracer.
20 kg was blown from the tuyere directly above the taphole, and at the same time, the Co concentration of the hot metal in the taphole was measured. The results are shown in Fig. 10.

The elapsed time T is judged to be "5 <T≤10 (minutes)" and does not satisfy the equation (1). Therefore, the restriction on the use of the tap hole is foreseen. Then, after 12 hours, it was determined that the two thermometers had recovered to the temperature before they naturally rose, and the risk of bottom brick wear was gone.

(Embodiment 4) The hearth gauge is 14.6 m, and the furnace volume is 4800.
The results of an actual furnace test performed on a blast furnace having four tap holes as in Example 1 at m ³ are shown below.

In this blast furnace, there is a fear of wear on the bottom of the furnace in a certain direction. Therefore, a tracer blowing test was periodically conducted to check the risk of bottom brick wear. A test was conducted in which a tracer was blown into the blast furnace during operation at a tap ratio of 1.9 and during tapping from a 1TH tap. The result is shown in FIG.

From FIG. 11, the elapsed time T from the start of the injection of the tracer to the rise in the Co concentration in the discharged hot metal is determined to be "15 <T≤20 (min)", and "the vicinity of the taphole is There is a high risk of wear of refractory bricks. " However, under the situation where a high tap ratio is required, it is not possible to restrict the use of the tap hole, and the operation is continued as it is. Then, after 20 hours, it was judged that both the bottom temperature of the taphole at 1TH and the temperature of the side wall of the hearth started to rise, and there was a risk of wear of the bottom brick.

Example 5 In the same blast furnace as in Example 4,
A test was conducted in which a tracer was blown at the tap hole of 3TH during operation at a tap ratio of 1.8. As a result, it was determined that "the vicinity of the taphole is in a state where there is a high risk of wear of refractory bricks".

Therefore, the use of 3TH tap hole is 25%
Restricted to. After 30 hours, it was determined that the thermometer on the tap side of 3TH had recovered to the temperature before rising, and the risk of brick bottom wear was gone.

Therefore, when the use restriction of the 3TH tap hole was canceled and the operation was started in the normal tap cycle,
After 20 hours, it was judged that both the bottom temperature and the hearth temperature at the 3TH tap hole began to rise, and there was a risk of wear of the bottom brick.

[0056]

As described above, according to the present invention, the risk of damage to the hearth of the blast furnace hearth is accurately grasped in a timely manner and the hot metal flow at the hearth bottom is controlled to locally erode the hearth brick. And it is possible to effectively extend the operating life of the blast furnace, and industrially useful effects are brought about.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the characteristics of a furnace bottom cross section and a hot metal flow field when a taphole penetrates into a coke packed bed.

FIG. 2 is a schematic view showing the characteristics of the furnace bottom cross section and the hot metal flow field when the taphole similarly penetrates into the coke-free layer.

[Fig. 3] "When the tracer is blown from directly above the taphole" for "when the taphole is intruding into the coke packed bed" and "when the taphole is intruding into the coke-free layer" 2 is an outline of a graph obtained by using a mathematical model for the "temporal change of tracer concentration in tapped hot metal."

[Fig. 4] Various blast furnace operating conditions (Case 1 and Case 2)
2 is a graph showing the result of numerical calculation of "temporal change of tracer concentration in hot metal in hot metal" by a mathematical model.

[Fig. 5] Various blast furnace operating conditions (Case 3 and Case 4)
2 is a graph showing the result of numerical calculation of "temporal change of tracer concentration in hot metal in hot metal" by a mathematical model.

[Fig. 6] Various blast furnace operating conditions (Case 5 and Case 6)
2 is a graph showing the result of numerical calculation of "temporal change of tracer concentration in hot metal in hot metal" by a mathematical model.

FIG. 7 is a graph showing the relationship between the tap ratio and the heat load applied to the refractory brick near the taphole when “there is a high risk of wear of the refractory brick near the taphole”. .

FIG. 8 is a schematic diagram showing a hearth sectional view of a blast furnace used in Examples 1 and 2 and a position of a thermometer.

FIG. 9 is a graph showing changes with time in Co concentration in Example 1.

FIG. 10 is a graph showing changes in Co concentration with time in Example 3.

FIG. 11 is a graph showing changes with time of Co concentration in Example 4.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kenji Katayama 4-53-3 Kitahama, Chuo-ku, Osaka Sumitomo Metal Industries Co., Ltd.

Claims (1)

[Claims] 1. A tracer is blown into the blast furnace together with hot air from a tuyere directly above the taphole during tapping or a tuyere closest to the taphole, and the tracer is discharged from the taphole to the outside of the furnace. While tracking the temporal change in the concentration of the tracer in the molten pig iron, the elapsed time T from the start of the blowing of the tracer to the increase in the concentration of the tracer in the discharged hot metal is detected, and the elapsed time T is expressed by the following formula. When the conditions shown in (1) are followed, the use of the taphole is restricted so that the amount of molten pig iron and slag discharged from the taphole is 50% or less of that during normal operation. Operating method. [Equation 1] [However, T: elapsed time (min), H: tap ratio at that time
(ton / day / m ³ )]