JPS5910404B2 - Blast furnace raw material charging method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for charging raw materials into a blast furnace, in which ores such as sintered ore or lump ore mixed with pellets are charged in multiple batches.

Normally, in blast furnace operation, ores and coke are charged into the furnace at a predetermined ratio in layers or in a mixed manner, and the charged materials are heated and reduced by the gas inside the furnace while smoothly falling downward.

In order to stabilize the furnace condition, the rate of rising gas in the furnace is made higher at the furnace center than at the furnace wall side, and the temperature at the furnace center is maintained high.

However, in a blast furnace, ore coke is charged into the inside from the outer periphery of the furnace mouth at the top of the furnace using a bell method or a distribution chute within the furnace, so the ore layer and coke layer accumulated inside the furnace are deposited on the furnace wall. It slopes downward from the center toward the center of the furnace.

The types of ores used include sintered ore, lump ore, and pellets, which are charged into the blast furnace either singly or in an appropriate mixture.

The physical properties of these ores are, for example, sintered ores, while lump ores have angular and irregular shapes.
Since pellets have a spherical shape with a smooth surface, the static inclination angle in the furnace is much smaller for pellets than for sintered ore or lump ore.

Therefore, when charging pellets mixed with sintered ore, lump ore, etc., the inclination angle of the ore layer in the furnace becomes smaller as the pellet mixing ratio increases, but the inclination angle of the coke layer in the furnace does not change. Because of this, the thickness of the ore layer near the center of the furnace becomes relatively large.

Therefore, the ratio between the ore layer thickness and the coke layer thickness in the vicinity of the furnace center increases, the ventilation resistance increases, and the amount of gas rising in the furnace at the furnace center decreases.

As a result, the heating reduction of the ores in the center of the furnace is delayed, while the gas flow rate in the furnace around the furnace walls increases, which adversely affects the smooth downward descent of the charge and the gas reduction efficiency, maintaining the furnace condition in a stable state. It becomes difficult to do so.

Conventionally, gas flow distribution adjustment means for overcoming these conditions and maintaining normal furnace conditions have been to adjust the gas flow distribution in the radial direction of the furnace by using a movable plate installed on the furnace wall or by changing the tilt angle of the chute for distributing the contents in the furnace. Attempts have been made to adjust the distribution of ore layer thickness, coke layer thickness, and mixed layer of ore and coke.

The present invention has been made in view of the above-mentioned problems when blending pellets. On the contrary, we invented a raw material charging method that effectively utilizes these characteristics.

In other words, in blast furnace operations where ores mixed with pellets are charged in multiple batches, the pellet content ratio in the ores charged onto the coke layer for the first time must be increased when aiming at central gas flow growth. On the other hand, when aiming at suppressing the central gas flow, the blast furnace raw material charging method is characterized in that the central gas flow is reduced.

According to the present invention, two effects can be achieved as shown below.

1. Even in blast furnace operation using pellets, the furnace condition can be stabilized and highly efficient blast furnace operation can be continued without causing troubles as in the past.

2. By utilizing the physical properties of pellets, a new distribution adjustment means is provided in place of conventional gas flow distribution adjustment means such as a movable plate provided on the furnace wall and a chute for distributing contents in the furnace.

The present invention will be specifically explained below.

The present inventors have discovered that CL in blast furnace operation in which pellets are charged.
When ores are charged in multiple batches, such as C↓min↓min↓, C↓Cmin↓min↓, the ores (hereinafter referred to as I{}) to be charged onto the coke layer and I Attention was paid to the following differences in the behavior of pellets in the ores (hereinafter referred to as ■÷) charged onto -e-.

(1) The pellets contained in I{} break down the coke layer charged before and flow the coke into the center. As a result, a mixed layer of coke and pellets is formed in the center, and ventilation in the center occurs. improve sex.

(2) The pellets contained in the I-E} flow into the center of the furnace at an angle of inclination unique to the ores containing pellets without disturbing the I-E} layer, increasing the thickness of the ore layer/coke layer in the center and aeration. make sex worse.

The reason why the above phenomenon (IX2) occurs is as shown in FIG. 1 atb, when pellets are charged onto a coke layer, the pellets are spherical, have a high bulk density, and have a large falling energy, so they have a strong tendency to sink into the coke layer.

As a result, the coke layer is broken and an avalanche phenomenon occurs, causing the broken coke to flow into the center, and at that time, it is determined that some beresoto, which behaves in the same way as coke, forms a mixed layer with coke in the center. be done.

On the other hand, as shown in Figure 1C, Beresoto charged onto the sintered ore and lump ore layer has a small difference in particle size and bulk density from the sintered ore and lump ore layer. This is thought to be due to the fact that the ore containing pellets is less likely to sink into the furnace and flows to the center of the furnace at an angle of inclination unique to ores containing pellets.

By the way, the above-mentioned phenomenon (lX2) is caused by the gas flow distribution in the furnace,
They have contradictory effects on air permeability, etc., and the phenomenon (1) is effective for improving air permeability by cultivating the center gas flow (increasing the center temperature), and the phenomenon (2) is effective for improving the air permeability by increasing the center gas flow (increasing the center temperature). decrease)
Effective in improving gas reduction efficiency.

Therefore, by appropriately adjusting the degree to which the contradictory phenomena (IX2) occur, that is, by adjusting the amount that breaks up the coke layer and the amount that flows into the center of the pellet, the overall pellet blending amount can be kept constant. Even if
It becomes possible to adjust the gas flow distribution in the furnace.

Specifically, when aiming at central gas flow growth, I{}-
The opposite is true when increasing the amount of pellets in the IIG and decreasing the amount of pellets in the IIG to suppress the central gas flow.

The adjustment allowance for the amount of pellets in I-{1} and the amount of pellets in II{}- is determined and set based on the difference between the target value and actual value of the central gas flow and air permeability at that time.

Also, when charging ores in three or more installments, the same applies to I.
The desired gas flow distribution can be obtained by adjusting the amount of pellets in the pellets and subsequent ores.

As a result, by implementing the present invention, even when the pellet blending ratio is high, there is no deterioration in air permeability or operational instability that occurs with conventional charging methods, and gas flow distribution control that effectively utilizes the physical properties of pellets. As a result, the optimum gas flow distribution can always be obtained and high efficiency operation of the blast furnace can be maintained.

Examples of the present invention will be described below.

FIG. 2 shows the relationship between the I+ pellet blending ratio, the ■min pellet blending ratio, and the sonde center temperature across the furnace mouth, air permeability, and gas utilization rate for a blast furnace with an internal volume of 2950771''.

The usage data is the seasonal average value for 6 months, and this figure shows that as the DI pellet blending ratio increases (as the TI pellet blending ratio decreases), the temperature at the center of the sonde across the furnace throat increases and the ventilation improves. However, it can be seen that the gas utilization rate is decreasing.

Figures 3a and b show the changes immediately before the T{} pellet blending ratio (IIG pellet blending ratio) was changed during the period shown in Figure 2 above.
It shows changes in blast furnace operating results for each of the immediately following two days, and the usage data is an 8-hour average value.

To explain with reference to FIG. 3a of the first embodiment, the temperature at the center of the sonde across the furnace mouth decreased and the ventilation of the entire blast furnace deteriorated, making it impossible to maintain good furnace conditions. E} Pellet increase, II + pellet decrease were performed.

As a result, after about 24 hours, the temperature at the center of the sonde across the furnace mouth increased, the ventilation improved, and the operating results were almost in line with the target, allowing the furnace condition to recover.

Figure 4 shows that the temperature at the center of the sonde across the furnace mouth decreased, and the ventilation of the entire blast furnace deteriorated, making it impossible to maintain good furnace conditions.

As a result, after about 24 hours, the temperature at the center of the sonde across the furnace mouth increased, the ventilation improved, and the operating results were almost in line with the target, allowing the furnace condition to recover.

Figures 3b and 3a are actions taken with the purpose of obtaining the opposite results, and in the example shown in this figure, ventilation was good and the situation was favorable for blast furnace productivity. Since the fuel ratio of the blast furnace was not favorable, the aim was to further increase the gas utilization rate and lower the fuel ratio.

From the figure, it can be seen that due to the decrease in I{}- pellets and the increase in ■G pellets, the temperature at the center of the sonde across the furnace mouth decreased, and the air permeability slightly deteriorated, or the gas utilization rate increased as expected.

The example shown in Fig. 3C also reduces I+ pellets in the same manner as Fig. 3B.
It can be seen that the relationships shown in Fig. 2 are satisfied, such as the decrease in the sonde center temperature across the furnace mouth and the improvement in gas utilization efficiency due to the increase in ÷ pellets.

[Brief explanation of drawings]

Figure 1 a shows that, for example, at C↓C↓ox↓minute↓, I{}
The inclination angle in the furnace of ■C before charging is shown. FIG. 1b shows the change in the inclination angle of ■C when IO consisting mainly of pellets is charged onto ■C charged previously. Figure 1C shows 14, which mainly consists of sintered ore and lump ore, ■C
Changes in the inclination angle of ■C when charging on top, and TI when charging ■once consisting of pellets on top of I-o-
} indicates the inclination angle. FIG. 2 shows the relationship between the I{} pellet blending ratio and the pellet blending ratio (■) with air permeability, gas utilization rate, and sonde center temperature across the furnace mouth. Figure 3 a, b, and c are T{l} pellet blending ratio TI{}-
These are examples showing the transition of blast furnace operation performance when changing the pellet blending ratio. FIG. 4 is an example showing the transition of blast furnace operating results when changing the IG pellet blending ratio.

Claims (1)

[Claims] 1. In blast furnace operations where ores mixed with pellets are charged in multiple batches, the pellet content ratio in the ores charged onto the initial coke layer should be increased if the aim is to develop a central gas flow. , on the other hand, when the central gas flow is to be suppressed, it is reduced.