JPH02236209A - Method for operating blast furnace - Google Patents

Abstract

PURPOSE:To improve the productivity by measuring distribution of pressure and temp. in height direction in a blast furnace and distribution of gaseous hydrogen utilizing ratio in radius direction in operation of the blast furnace charged with high reactive coke and adjusting blending ratio of pellet. CONSTITUTION:The blending ratio of the pellet at the time of operating the blast furnace by charging the high reactive coke, is adjusted so that the pressure difference and/or the temp. at each stage come to the preset reference values by measuring the pressure distribution and/or the temp. distribution in the height direction in the blast furnace. Further, by measuring the distribution of gaseous hydrogen utilizing ratio in the radius direction in the blast furnace, this is adjusted so as to come to the preset reference value. By this method, the gas utilizing ratio is improved and also the blast furnace operation with low coke ratio can be executed, and the productivity can be improved.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention improves productivity by using coke with increased reactivity as part or all of the coke charged from the top of the furnace. Regarding blast furnace operation method.

(Prior art) In a normal blast furnace, iron ore and coke are charged in layers from the furnace stage, and the iron ore is reduced in the furnace, and then reduced and melted into a metallic state to produce smelt. are doing.

At this time, in order to increase the reduction efficiency of iron ore,
Publication No. 43169 discloses that iron ore and small coke are mixed in advance, and that this mixture and normal coke are charged in layers. By using iron ore mixed with coke in advance in this way, the ventilation inside the furnace is improved and its reducing performance is improved.

Furthermore, in Japanese Patent Application No. 62-193457, the present inventors used small-sized highly reactive coke of 15 mm or less, mixed the highly reactive coke with ordinary coke or ore, and charged it into a blast furnace. We proposed a blast furnace operating method that lowers the temperature of the thermal reserve zone of the blast furnace and increases the reaction efficiency of the blast furnace.

(Problem to be Solved by the Invention) By the way, in order to improve the reaction efficiency of a blast furnace, it is effective to use small-sized highly reactive coke mixed with ore or coke, and the reaction efficiency can be improved by operating this blast furnace. The effect enables low fuel ratio operation.

However, if the gas flow becomes unbalanced and a region of low gas flow occurs in the blast furnace shaft, as is often the case during conventional low fuel ratio operations, a low-temperature thermal storage zone of 600-700°C is likely to occur. In this area, sinter reduction and pulverization are promoted, resulting in poor ventilation of the blast furnace shaft, which often results in delays in ore reduction, poor lowering of the charge, and other obstacles to stable blast furnace operation.

Moreover, the temperature distribution in the height direction inside the blast furnace is disclosed in Japanese Patent Application Laid-Open No. 591691.
As disclosed in Japanese Patent Publication No. 7, the pressure distribution in the height direction is measured using a vertical sonde, and the pressure distribution in the height direction is
As disclosed in Japanese Patent No. 9272, the static pressure of the furnace wall is measured.

However, this information has not yet been used to adjust the amount of pellets used.

Furthermore, in Japanese Patent Application Laid-Open No. 62-054006,
A method is disclosed for detecting the temperature distribution in the furnace by measuring the hydrogen utilization rate or the hydrogen utilization rate/Go utilization rate in the upper part of the blast furnace furnace or shaft. However, this information has not yet been used to adjust the amount of pellets used.

Therefore, the present invention aims to reduce the temperature of the thermal storage zone by increasing the reactivity of the coke charged into the blast furnace, thereby promoting the reduction reaction of iron ore throughout the blast furnace, and the reduction reaction being carried out at a low temperature. The purpose is to reduce the amount of increase in powder ratio due to reduction and powdering of sintered ore, which is promoted by sinter reduction, and to produce melt with high productivity.

(Means and effects for solving the problem) In order to achieve the object, the blast furnace operating method of the present invention is designed to reduce the pressure in the height direction inside the blast furnace when charging highly reactive coke into the blast furnace and performing the operation. The feature is that the distribution and/or temperature distribution is measured, and the pellet usage ratio is adjusted so that the differential pressure and/or temperature at each stage becomes a preset reference value. The blast furnace is characterized by measuring the hydrogen gas utilization rate distribution in the radial direction inside the blast furnace and adjusting the pellet usage ratio so that the hydrogen gas utilization rate distribution reaches a preset reference value. do.

First, we will discuss highly reactive coke.

The highly reactive coke used in the present invention is JISK215
JIS when measured by the reactivity test method of 1-1977
It is desirable that the reactivity is 30% or more. Its value is 3
When it is less than 0%, there is almost no decrease in the temperature of the thermal storage zone, which will be described later. Furthermore, even with highly reactive coke, it is necessary to maintain high strength, and it is desirable to maintain the same strength as normal coke.

Methods for preparing highly reactive coke with high strength include a method of adding an alkaline aqueous solution to high-strength ordinary coke, and a method of molding steam coal and carbonizing it.

Highly reactive coke replaces the entire amount of coke that is normally charged from the top of the furnace, and is charged in layers or mixed with iron ore.

Further, it can replace a part of the coke that is normally charged from the top of the furnace and can be mixed with iron ore and/or normal coke and charged in advance. The particle size of the highly reactive coke at this time is preferably 15 mm or less. When the particle size is 15III1 or less, the surface area of coke per unit weight increases, and the proportion contributing to the reaction increases.

Since this highly reactive coke has high reactivity, an interfacial reaction in which CO in the furnace comes into contact with the surface of the coke and becomes CO takes place smoothly. In addition, as a result, the C generated in the furnace
The O gas effectively reacts with the iron ore to promote the reaction of reducing it to a lower oxide or metal state.

The coke gasification reaction of c+cot =2co can reduce the temperature of the zone. For example, when using the conventional method, a heat reserve zone of about 1000℃ is generated, and its value hardly changes, but by using highly reactive coke, the temperature of the heat reserve zone is increased to 900-950℃. It becomes possible to lower the amount. As a result, there is more room at the reduction equilibrium point, and the reduction progresses more.
Improved shaft efficiency, indirect reduction rate, and Co gas utilization rate,
Coke ratio can be lowered.

Next, we will discuss the reduction phenomenon of sintered ore.

The use of highly reactive coke improves the reduction efficiency, but as a result of promoting reduction at low temperatures, reduction powdering of the sintered ore is promoted, the amount of powder generated increases, and the ventilation inside the blast furnace is reduced. Unless measures are taken to suppress this deterioration, the effects of highly reactive coke cannot be maximized and high productivity cannot be ensured.

When the air permeability deteriorates, the temperature distribution in the height direction inside the blast furnace changes.
A low-temperature thermal storage zone of 0 to 700° C. is generated, and a portion where the differential pressure is almost zero is generated in the static pressure distribution on the furnace wall. Also, 6
Due to the progress of the water gas shift reaction in the low-temperature heat storage zone of 00 to 700°C, the hydrogen gas utilization rate decreases.

Figure 4 compares the amount of reduction and pulverization of sintered ore and pellets during the formation of the low-temperature thermal storage zone mentioned above.As seen in the figure, the amount of reduction and pulverization of pellets is half that of sintered ore. Since the amount of sintered ore is small, replacing a part of the sintered ore with pellets is a means of suppressing the amount of reduction and powdering.

Figures 1 to 3 show the powder ratio in the furnace in each operating state at the standard value (the value during operation when the weight ratio of iron in the pellets per ton of pig iron is 7%, that is, the pellet weight is 100 kg/t-pig). ) shows the rate of increase in the amount of pellets used to maintain the powder rate in the furnace at approximately the same level as the powder rate in the furnace. Figure 2 shows the relationship between the static pressure differential level at the furnace wall and the rate of increase in the amount of berebut used, and Figure 3 shows the relationship between the hydrogen gas utilization rate measured by a horizontal sonde and the rate of increase in the amount of pellets used. Indicates the relationship between The percentage increase (%) in the amount of pellets used here refers to the weight percentage of iron in the pellets per ton of pig iron after replacing some of the sintered ore with pellets, and This is the difference between the weight ratio of iron in pellets per ton of pig iron before replacing with iron, expressed as a percentage.

The standard value for the length of the low-temperature heat storage zone is Om, and the furnace wall static value is 50.
%.

For example, in the case of Figure 1, in a blast furnace where the length of the low-temperature heat storage zone is approximately 6 m, by setting the rate of increase in the amount of pellets used to 15%, the powder ratio in the furnace can be maintained at the same level as the standard value. becomes possible. In the case of Figure 2, the differential pressure of the static pressure on the furnace wall is 1
8 g/cm'', by increasing the pellet usage rate by 15%, and in the case of Fig. 3,
In a blast furnace with a hydrogen gas utilization rate of 40%, by increasing the rate of increase in the amount of pellets used by 9%, it is possible to achieve a powder ratio in the furnace similar to the standard value, and this operation suppresses the deterioration of air permeability. , operations can be aimed at eliminating the low-temperature thermal reserve zone.

In addition, when the hydrogen gas utilization rate exceeds 50% or when the differential pressure of the static pressure at the furnace wall exceeds 60 g/cm,
There is no need to change the amount of pellets used.

In the present invention, the temperature distribution in the height direction inside the blast furnace is 600 to
Detect the occurrence of a 700℃ low-temperature thermal storage zone by measuring with a vertical sonde, etc., and/or measure the static pressure on the furnace wall to detect the occurrence of a poor ventilation zone where the differential pressure in the pressure distribution in the height direction is almost zero. Alternatively, the hydrogen gas utilization rate at the top of the blast furnace and/or the shaft of the blast furnace can be detected by measuring with a horizontal sonde, etc., and based on the results, a part of the sintered ore that is significantly reduced and powdered can be reduced. By substituting pellets with less pulverization and suppressing the amount of reduction pulverization, the above-mentioned low-temperature heat storage zone and/or poor ventilation zone can be eliminated and stable blast furnace operation can be performed.

In addition, the reduction powder index of sintered ore is measured by the sample (15 to 20 m
m, 500 g) to reducing gas (Co 30%-N, 70
%, 15NN/sin) at 550°C for 30 minutes, and then rotated at 900 rotations (30 rpm) in a rotating tester.
8 30 minutes) after 30 minutes).

(Example) Hereinafter, the features of the present invention will be specifically explained with reference to Examples.

Table 1 shows a comparison of blast furnace operation using highly reactive coke with conventional methods.

The target blast furnace is a medium-sized blast furnace with an internal volume of 3000 m3. In the conventional method, iron ore and normal coke are charged from the top of the furnace at a ratio of O/C = 3.2, and the flame temperature in front of the tuyere is set at 2270 °C (hot air temperature 1100 °C). ℃, added moisture 35 g/Ni3, no pulverized coal blowing)).
Comparative Example) A sintered ore with a reduction powdering index of 38% was used.

In Example 1, 35% of normal coke was replaced by highly reactive coke with a JIS reactivity of 45% and a particle size of I51III1, and the highly reactive coke was mixed with iron ore and charged. Using a sonde, we detected a low-temperature thermal storage zone of 600 to 700 degrees Celsius over approximately 4 meters above the blast furnace shaft (an example of operation before pellet preparation), so we reduced the amount of sintered ore according to Figure 1 and reduced the rate of increase in the amount of pellets used. 8%
The results of operation with increased amount are shown (example of operation after pellet adjustment).

In Example 2, in the same operating mode as in Example I, when the pressure distribution in the height direction inside the blast furnace was measured and the differential pressure at each stage was detected,
Compared to the standard value 60 g7cm, the differential pressure is 18 g/
cta” (operation example before pellet adjustment), the pellet usage It (T.F.
The operation state when the increase rate of e65%) was increased by 15% is shown (operation example after pellet adjustment).

In Example 3, the temperature distribution in the height direction inside the blast furnace was measured using a vertical sonde, and the pressure distribution in the height direction inside the blast furnace was measured in the same operating mode as in Example 1. It shows the operational results when the usage ratio is increased or decreased and the operation continues to satisfy each standard value.

In Example 4, the entire amount of normal coke was replaced with highly reactive coke with a JIS reactivity of 43%, and the hydrogen gas utilization rate in the radial direction inside the blast furnace (-H,0/(H,+
}{ to ) ) distribution was detected, it was detected that the hydrogen gas utilization rate at a position lm from the blast furnace wall was 1O% lower than the standard value (hydrogen gas utilization rate 50%). (Example of operation before pellet adjustment) and operation results when increasing the rate of increase in the amount of pellets used by 9% are shown (Example of operation after pellet adjustment).

In Examples 1, 2, and 3.4, a reduction in coke ratio was achieved compared to the comparative example.

In addition, examples! , 2.4, the operating results before pellet adjustment are smaller than the operating results after changing the pellet usage ratio, and the degree of decrease in coke ratio is smaller, and the hot metal temperature and hot metal [
Si] is also high, and blast furnace operation is not efficient. As shown in Example 3, by controlling the temperature distribution in the height direction inside the blast furnace using a vertical sonde and measuring the pressure distribution in combination, blast furnace operation can be stabilized and operation with a reduced coke ratio is possible. Become.

(Effects of the Invention) As described above, in the present invention, by using highly reactive coke, the gas utilization rate can be increased and blast furnace operation can be performed with a small coke ratio. We also implemented measures to suppress poor ventilation by lowering the temperature of the heat storage zone.
Since a stable gas flow can be ensured, shaft efficiency can also be increased. In this way, according to the present invention, the productivity of blast furnace operation can be improved.

[Brief explanation of drawings]

Figure 1 shows the length of the low-temperature heat storage zone in the height direction inside the blast furnace and the rate of increase in the amount of pellets used. Figure 2 shows the difference in static pressure at the furnace wall and the rate of increase in the amount of pellets used. , Figure 3 shows the rate of increase in hydrogen gas utilization rate and pellet usage.
FIG. 4 is a diagram showing the relationship between sintered ore, pellets, and reduction powdering rate. 2nd turtle drawing exhibition

Claims (2)

[Claims] (1) When charging highly reactive coke into a blast furnace and operating it, the pressure distribution and/or temperature distribution in the height direction inside the blast furnace is measured, and the differential pressure and/or temperature at each stage is adjusted to the reference value. A blast furnace operating method characterized by adjusting the pellet usage ratio so that the ratio of pellets used is adjusted. (2) When charging highly reactive coke into a blast furnace and operating it, the hydrogen gas utilization rate distribution in the radial direction within the blast furnace is measured, and the hydrogen gas utilization rate distribution is adjusted to a preset standard value. A blast furnace operating method characterized by adjusting the pellet usage ratio.