JPH0699733B2 - Blast furnace control method in pulverized coal fuel injection operation. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention adjusts the descent rate of blast furnace interior charges, particularly the descent rate on the peripheral side of the furnace relative to the descent rate on the central side of the furnace. The present invention relates to a method of improving the operating efficiency of a blast furnace by doing so.

[Prior Art] In the integrated steelmaking by the blast furnace-converter, improving the operation efficiency of the blast furnace is one of the most important issues in reducing the ironmaking cost. Therefore, efforts are being made to estimate the condition inside the blast furnace, which is a black box, using various methods, and to grasp the correlation between the operating conditions and the estimation results to contribute to the improvement of control accuracy.

As a means for improving the operating efficiency of the blast furnace and improving the productivity, for example, formation of a central flow and stabilization of the unloading are known, but the amount of heat generated in the blast furnace is as effective as possible in the furnace. It is considered that it is effective to achieve the above purpose. For example, the heat generated by the flame formed at the tuyere should be utilized inside the furnace, but it is a loss in the heat economy to transfer this to the furnace wall side and dissipate it outside the iron skin, In addition to the increase in the coke ratio due to the decrease in the utilization rate of coke, it is also inconvenient from the viewpoint of maintenance of the furnace refractory wall. Therefore, it is not possible to establish a control method by grasping the combustion situation of the fuel blown into the blast furnace, how to efficiently use the heat generated in the raceway in the blast furnace, and how to reduce the heat removal amount to the furnace wall. It must be one of the challenges in blast furnace operation.

On the other hand, as for the fuel to be injected into the blast furnace, the pulverized coal fuel has been increasingly used since the change of petroleum circumstances, and it has been found that it is very dangerous to transfer the knowledge obtained in the conventional heavy oil injection operation. Therefore, it was necessary to reconsider the pulverized coal fuel injection operation from scratch, and the problems in using pulverized coal fuel were reexamined.

The inventors of the present invention also conducted research on problems in pulverized coal injection operation from such a viewpoint, for example, points such as combustibility and molten ash content adhesion, and for example, pulverized coal fuel injection technology as disclosed in JP-B-60-53081. Has been developing. However, the conventional development direction is to prevent the adhesion trouble due to the intervening ash content in the pulverized coal and to exhibit the best combustibility, in other words, to have the drawback that the characteristics as a fuel are lower than those of heavy oil and the like. The biggest concern was whether it would be well covered.

[Problems to be Solved by the Invention] Since some satisfactory results have been obtained in these items, further research is conducted from the viewpoint of positively utilizing the pulverized coal fuel injection technology to improve the efficiency of blast furnace operation. A study was conducted.

The heat balance in the blast furnace operation is closely related to the operation efficiency, and it is very important to effectively use the heat generated by the combustion of the fuel injected from the tuyere for the reduction of iron ore. However, in the blast furnace operation to which the pulverized coal fuel injection technology developed so far is applied, a considerable amount of the generated heat is consumed for heat transfer to the blast furnace refractory wall, and the coke descending directly above the raceway. Oxidation reaction of: C + CO ₂ → 2CO tended to be insufficient.

On the other hand, the dropping phenomenon of the charge in the blast furnace is based on the consumption of C in the coke due to the above-mentioned oxidation reaction. However, supplying pulverized coal into the blow pipe causes consumption of O _{2 in} the hot air due to this pulverized coal, and therefore reduces O ₂ supplied to the oxidation reaction, which in turn leads to reduction of coke consumption. It causes a decrease in the charge descent rate. This phenomenon is also confirmed from the fact that the pulverized coal blowing operation is more remarkable than the so-called all coke operation. Thus, when the coke descent rate on the peripheral side of the furnace slows down, the coke on the center side of the furnace is relatively rapidly oxidized and falls, so that the cohesive zone shape in the blast furnace is optimized (inverted V shape). It seems that there are signs that it becomes difficult to hold and that it tends to take on the W shape, which is said to be less preferred.

From such a point, it is necessary to establish operating conditions such that the descending speed of the coke on the peripheral side in the blast furnace is relatively faster than the descending speed on the center side to form the inverted V-shaped cohesive zone shape. occured. Therefore, the present inventors further researched, and if the combustibility (in other words, the consumption amount due to the combustion of pulverized coal) when the amount of pulverized coal injection was constant was controlled, the descent rate of the charge on the inner wall side would be centered. The idea that it may be possible to adjust relative to the descending speed of the side load,
We decided to develop such control means.

[Means for Solving the Problems] In the configuration of the present invention completed under the above problems, a pulverized coal fuel discharge lance is inserted into a blow pipe connected to a blast furnace tuyere, and discharged from the discharge lance. When the pulverized coal fuel is blown into the blast furnace by the hot air flow into the blast furnace, the charge on the peripheral side of the furnace is adjusted by adjusting the position of the discharge tip of the pulverized coal fuel discharge tip in the blow pipe length direction. The point is that the descent rate is adjusted relative to the charge descent rate on the center side of the furnace.

[Operation] The gist of the present invention is to relatively adjust the charge descent rate on the peripheral side of the furnace by adjusting the pulverized coal fuel discharge position into the blow pipe in the length direction of the blow pipe. It is a thing. Such a control technique in a blast furnace has never been carried out in the past, and the present invention is regarded as an arrow.

FIG. 2 is a schematic view showing a pulverized coal fuel injection device in an actual furnace used in the experiment of the present invention, wherein 1 is a tuyere, 2 is a blow pipe, and 3 is a pulverized coal fuel discharge lance. In the figure, the lance insertion hole 4 is provided so that the mounting position of the pulverized coal fuel discharge lance 3 can be arbitrarily changed along the length direction of the blow pipe 2.
A large number of lances are provided, and the plug 5 is provided when the lance 3 is not inserted. Then, the boundary position between the tuyere 1 and the blow pipe 2 is S
, The tip position P of the discharge lance 3 is the boundary position S.
Positive (+) in the hot air blowing upstream side (right side in the figure) and negative (-) in the downstream side (outward) +200 mm
The following experiments were performed for the case of -100 mm and the case of -100 mm. That is, in each of the above two cases, the pulverized coal fuel injection operation was individually performed, the temperature at each point of the blast furnace walls was measured, and the temperature measurement values were plotted in the height direction of the blast furnace. The results shown in Fig. 1 were obtained. Was obtained. The black circles in Fig. 1 show the temperature distribution in the furnace wall height direction when the pulverized coal fuel is discharged from the boundary position S to the upstream side + 200mm, and the white circles in the same figure are the downstream side. The figure shows the temperature distribution in the furnace wall height direction when discharged to a point of -100 mm.
As is apparent from this graph, the discharge position of the pulverized coal fuel is different in the lengthwise direction of the blow pipe, so that a remarkable variation is observed in the distribution of the furnace wall temperature in the height direction.
That is, when the discharge position of the pulverized coal fuel approaches the upstream side of the blow pipe, the wall side temperature in the furnace side rises, and conversely, when the discharge position approaches the downstream side of the blow pipe, the wall side temperature in the furnace side decreases. This is considered to mean the following. That is, when the pulverized coal fuel is discharged to the upstream side of the blow pipe, the ignition of the fuel starts relatively early and the combustibility at the tuyere improves, and as a result, as described above, in the raceway. Combustion failure of charging coke due to reduction of oxygen content, that is, W-shaped softening cohesive zone due to decrease in descent rate (consequent promotion of peripheral flow), and tuyere due to temperature rise in blow pipe The temperature of the furnace wall is raised with the decrease in heat removal capacity of the cooling water. In other words, as a result of an increase in the amount of heat loss from the furnace wall, the utilization efficiency of the generated heat in the blast furnace decreases, the coke ratio in the blast furnace operation increases, and the furnace heat fluctuation also increases, which reduces productivity and stabilizes the furnace condition. Inconvenience such as deterioration of sex occurs. Therefore, in this case, the amount of coke digested on the peripheral side of the blast furnace tends to decrease, and the descending speed of the blast furnace interior contents becomes gentle. Relatively speaking, this means that the rate of fall of the charge on the peripheral side is slower than that on the center side in the blast furnace, and therefore the softening melt formed by the progress of reduction of iron ore. The landing profile becomes W-shaped, and a state unfavorable for blast furnace operation is formed.

On the other hand, when the pulverized coal fuel is discharged to the downstream side of the blow pipe, the ignition of the fuel is delayed and the combustibility at the tuyere tip deteriorates. Therefore, the amount of heat removed in the direction of the furnace wall decreases, and the temperature rise in the furnace wall becomes extremely gentle as shown in FIG. In this regard, in Japanese Patent Publication No. 60-53081, when the discharge position of the pulverized coal fuel shifts to the downstream side of the blow pipe, the pulverized coal enters the furnace packed bed due to incomplete combustion in the blow pipe and raceway. I was worried that it would accumulate and cause a problem of deteriorating breathability. For this reason, the discharge position of the pulverized coal fuel was set to the upstream position in the blow pipe, but this also caused the disadvantages such as the improvement of the coke ratio and the frequent occurrence of furnace heat fluctuations as described above. . On the other hand, when the discharge position of the pulverized coal fuel is set to the downstream side of the blow pipe as studied in the present invention, the heat removal amount toward the furnace wall is reduced as described above, so that the generated heat amount is effectively used. It was found that not only the effect of improving the coke ratio can be obtained, but also unburned pulverized coal is gasified earlier than coke and there is no fear of adversely affecting the air permeability of the furnace.

Incidentally, FIG. 3 is a graph correlating the burning rate of the pulverized coal fuel in the blow pipe with the heat loss of the blast furnace abdomen, and it can be seen that the abdominal heat loss decreases as the burning rate of the pulverized coal fuel decreases.

After all, the present invention controls the heat removal amount to the inner wall surface of the furnace by changing the discharge position of the pulverized coal fuel into the blow pipe in the length direction of the blow pipe, thereby adjusting the coke ratio and adjusting the coke ratio. It controls the descent rate of the charge relative to the descent rate of the charge on the center side of the furnace, but generally speaking, the coke ratio is reduced to decrease the rate of fall of the charge on the periphery of the furnace. Since it is significant to the operation of the blast furnace to form the inverted V-shaped cohesive zone shape, it is recommended to select the discharge position of the pulverized coal fuel into the blow pipe as far downstream as possible. When it is set on the upstream side, it is preferable to stop at about 100 mm upstream from the boundary position between the tuyere and the blow pipe. On the other hand, on the downstream side, the limit is 300 mm downstream from the boundary position, and if it is on the downstream side, the combustibility becomes extremely poor, and the purpose of fuel injection cannot be met.

[Example] FIG. 3 shows the pulverized coal fuel discharge position when the position is adjusted within the range of 100 mm on the upstream side and 100 mm on the downstream side around the boundary position. Is obtained, and the K value decreases when the discharge position is set to the downstream side, and it can be seen that the heat load on the furnace wall decreases.

FIG. 4 shows the wind pressure index (dimensionless) obtained when the discharge position is controlled in a wider range from the downstream side to the upstream side, and shows that the higher the wind pressure index, the larger the air permeability. As is apparent from this graph, when the distance exceeds 300 mm on the downstream side of the boundary position as a reference, unburned pulverized coal fuel is excessively deposited and a ventilation obstacle is generated.

[Advantages of the Invention] Since the present invention is configured as described above, control is performed so that the charge descending speed on the peripheral side in the furnace in blast furnace operation is made relatively faster than the descending speed of the center-side charge. You can
It has become possible to improve the coke ratio and promote the inverse V-shape of the softened cohesive zone shape.

[Brief description of drawings]

Fig. 1 is a graph showing the distribution of the furnace wall temperature seen in the height direction of the blast furnace, Fig. 2 is an explanatory view showing the structure of the blow pipe part, and Fig. 3 is the pulverized coal fuel discharge position and the temperature of the lower part of the furnace ( FIG. 4 is a graph showing the relationship between the pulverized coal fuel discharge position and the wind pressure index.

Claims (2)

[Claims] 1. A pulverized coal fuel discharge lance is inserted into a blow pipe connected to a blowing tuyere of a blast furnace, and the pulverized coal fuel discharged from the discharge lance is blown into the blast furnace by a hot air flow in the blow pipe. By adjusting the position of the pulverized coal fuel discharge tip in the discharge lance in the length direction of the blow pipe, the charge lowering speed on the peripheral side of the furnace with respect to the charge lowering speed on the central side of the furnace is adjusted. A method for controlling a blast furnace, which comprises performing relative adjustment. 2. A blast furnace control method comprising controlling the heat load on the circumferential refractory wall in the lower part of the furnace body by performing the relative adjustment described in claim 1.