JPH02200712A - Method for operating blast furnace - Google Patents

Abstract

PURPOSE:To improve the utilizing ratio of CO gas and to produce molten iron at low coke ratio and good productivity by replacing a part or the whole of coke for metallurgy with the coke improving the reactivity, making suitable of pressure distribution and temp. distribution in height direction in a blast furnace and adjusting the reducing powdering index of sintered ore at the time of operating the blast furnace. CONSTITUTION:A part or the whole of the coke for metallurgy charged in the blast furnace is replaced with the high reactive coke having >=30% JIS reactivity. In this result, reducibility of the sintered ore is improved, but as the reduction at low temp. is promoted and gas permeability in the blast furnace is lowered, the development of the low temp. heat holding zone in the temp. distribution in the height direction in the blast furnace, is detected with a vertical sonde, etc. Further, the development of poor gas permeability body, where the differential pressure in the pressure distribution in the height direction comes to almost zero, is measured, and by this result, the reducing powdering index of the sintered ore is restrained, and the existences of the low temp. heat holding zone and poor gas permeability zone are cancelled and the molten iron is produced at the low coke ratio and the excellent productivity.

Description

Detailed Description of the Invention (Field of Industrial Application) 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. Concerning blast furnace operation methods.

(Prior art) In a normal blast furnace, iron ore and coke are charged in layers from the top of the furnace, the iron ore is pre-reduced in the furnace, and then reduced and melted into a metallic state to produce hot metal. is manufactured. At this time, in order to improve the reduction efficiency of iron ore,
No. 3169 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 reducibility is improved.

(Problem to be solved by the invention) By the way, the coke conventionally used as a charging material for blast furnaces is required to have a certain strength so as not to be pulverized inside the blast furnace, so it is necessary to use coke with low reactivity. has been done. Therefore, in order for the next coke gasification reaction to occur in the furnace, the thermal storage zone temperature of the blast furnace is about 1000° C., and a temperature higher than that is required.

C + CO2 → 2CO Because the temperature of the thermal storage zone is high, the amount of CO gas generated by the above reaction does not increase, and the reduction/[equilibration point] does not change, so the shaft efficiency, indirect reduction rate, CO gas utilization rate is also improved beyond a certain value.

do not.

Moreover, the temperature distribution in the height direction inside the blast furnace is
As disclosed in Japanese Patent Publication No. 17, the measurement is carried out using a vertical sonde, and the pressure distribution in the height direction is as disclosed in Japanese Patent Application Laid-open No. 49-
As disclosed in Japanese Patent No. 79272, the static pressure of the furnace wall is measured, but this information has not yet been used to control the quality of sintered ore.

Therefore, in the present invention, by using highly reactive coke to be charged into the blast furnace, the temperature of the thermal storage zone is lowered to promote the reduction reaction of iron ore, and the reduction reaction is carried out at a low temperature. The purpose of this method is to prevent the increase in reduction powdering of sintered ore that occurs as a result of acceleration, and to produce hot metal 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 has a JIS reactivity of 3.
When operating a blast furnace with highly reactive coke of 096 or higher, the pressure distribution and/or temperature distribution in the height direction within the blast furnace is measured, and the differential pressure and/or temperature at each stage becomes the standard value. It is characterized by adjusting the reduction powdering index of the sintered ore.

First, let's talk about highly reactive coke.

The highly reactive coke used in the present invention is JISK 21
J when measured by the reactivity test method of 5+ -1977
It is necessary that the IS reactivity is 30% or more.

The numerical limitation of 30% is based on patent application No. 1.93457.
As shown in the issue, the effect is hardly seen up to 20% from actual furnace test results.

Further, the highly reactive coke replaces a part of the coke that is normally charged from the top of the furnace, and is charged after being mixed with iron ore and/or normal coke in advance.

The particle size of the highly reactive coke at this time is preferably 15 mm or less. When the particle size is 15 mm or less, the surface area of coke per unit m* increases, and the proportion contributing to the reaction increases. On the other hand, the particle size is 15
When m+i is exceeded, the inside of the coke undergoes a gasification reactionff
The ratio of effective utilization will decrease.

Additionally, it replaces the entire amount of coke that is normally charged from the top of the furnace, and is charged in layers with iron ore. The particle size of the highly reactive coke at this time is about the same as that of normal coke. It is preferable to maintain strength that does not deteriorate when high reactivity is achieved.

This highly reactive coke is prepared, for example, as follows. One is that it is not suitable for metallurgical coke production.
The method is to partially blend highly reactive slightly non-caking coal, or coal, into raw coal. In addition, small amounts of limestone, iron ore, and alkalis, which act as catalysts to promote reactions, are also added to coking coal.

Since this highly reactive coke has high reactivity, an interfacial reaction in which CO2 in the furnace contacts the surface of the coke and turns into CO occurs smoothly. Moreover, the reaction in which the CO gas generated in the furnace as a result reduces the iron ore to a lower oxide or metal state is also promoted.

Since the coke gasification reaction of C+CO, →2C0 is an endothermic reaction, the temperature of the heat storage zone in the blast furnace shaft can be lowered. 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 to 950℃. This makes it possible to lower the energy consumption.

As a result, the reduction progresses more because there is more room to reach the reduction equilibrium point, and more CO gas m is produced than before because coke gasification progresses at a lower temperature, which improves shaft efficiency and indirect reduction rate. , the CO gas utilization rate is improved, and since indirect reduction is an exothermic reaction, the coke ratio can be lowered.

Next, we will discuss the reduction and powdering adjustment 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 fully demonstrated and high productivity cannot be ensured.

When air permeability worsens, the temperature distribution in the height direction inside the blast furnace will change.
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.

In the present invention, the temperature distribution in the height direction inside the blast furnace, which occurs as a result of promoting sintered ore reduction and pulverization and deteriorating air permeability,
The occurrence of a low-temperature heat retention zone of ~700°C is detected by high-I measurement using a vertical sonde, etc., and/or the occurrence of poorly ventilated bodies where the differential pressure in the pressure distribution in the height direction is almost zero. is detected by measuring the static pressure on the furnace wall.

As a result, by suppressing the reduction pulverization index of the sintered ore and eliminating the above-mentioned low-temperature thermal storage zone and/or poor ventilation zone, stable blast furnace operation can be performed.

The reduced pulverization index of sintered ore can be adjusted by adjusting the sintering raw material mix and sintering operation (adjusting the basic unit of coke breeze, etc.), and by adding seawater or blast furnace thickener to the finished sintered ore. An aqueous solution containing chlorine ions (CN-) such as water may be added.

Relationship between the degree of occurrence of the above-mentioned low-temperature thermal preservation zone (length of preservation zone in the height direction) and/or degree of occurrence of poor ventilation zone (level of differential pressure) and the suppression width of the sinter reduction powdering index Regarding this, offline experimental results may be used, or actual reactor use test results may be employed.

In addition, the reduction powdering index of sintered ore is sample (], 5 to 2
hm, 500r) to reducing gas (CO3O%-N270%
, 15NN/1lin) at 550°C for 30 minutes, and then in a rotary tester at 900 rpm (30"pm).
It is expressed as the weight percentage (%) after 30 minutes).

(Example) Table 1 shows a comparison of blast furnace operation using highly reactive coke with a conventional method.

The target blast furnace is a medium-sized blast furnace with an internal volume of 3000 rri',
In the conventional method, iron ore normal coke is charged from the top of the furnace at a ratio of 0/C-3.2, and the flame temperature in front of the tuyere is set to 2270.
℃ (Hot air temperature 1100℃, added moisture 35f/N, pulverized coal injected) to produce hot metal.

was. A sintered ore with a reduced powdering index l-1 of 38% was used (Comparative Example 2).

In Example 1, 15% of the normal coke was added to J 1. Highly reactive coke with S reactivity of 35% and particle size of 15 mm (,,:
The highly reactive coke was mixed with iron ore and charged, and the temperature distribution in the height direction inside the blast furnace was adjusted to 11F using a vertical sonde.
The graph shows the results of operation in which in-blast furnace thickener water was added to the finished sintered ore to lower the reduction pulverization index when a low-temperature thermal preservation zone of 500 to 700°C was detected.

In Example 2, the entire amount of normal coke was converted into J'lS reactivity 3
The highly reactive coke was replaced with 0% highly reactive 1-coke, and the highly reactive coke was charged with iron ore in a layered manner, and the static pressure in the height direction of the furnace wall was increased to 11%.
The results are shown in which the sintering operation was performed by increasing the basic unit of coke breeze and decreasing the reduction pulverization index when P1 was constant and the differential pressure was close to zero.

Example' 15% of the normal coke was converted to JIS reactivity 3.
5%, highly reactive coke with a particle size of 15 mm, and the highly reactive coke was mixed with normal coke and iron ore by 1/2 and charged, and the temperature distribution in the height direction inside the blast furnace was measured using a vertical sonde. 1. When a low-temperature thermal storage zone of 500 to 700°C is detected, and when the static pressure in the height direction of the furnace wall is measured and the differential pressure is close to zero, the finished sintered ore This shows the results of operation by adding seawater to lower the reduction powdering index.

Example 1. ．． In both Comparative Example 2 and Comparative L2, a reduction in the coke ratio was achieved.

In addition, Comparative Example 1 is a case in which the detection of the low-temperature thermal storage zone using the C vertical sonde and the adjustment of the sintered ore reduction pulverization index in Example 1 were not performed, and the coke ratio was lowered by 7 compared to Example]. The blast furnace temperature is low, and the hot metal temperature and Si content in the hot metal are also high, making it difficult to operate the blast furnace efficiently.

/'' Figure 1 shows the relationship between the length of the low-temperature heat storage zone used in Example 1 and the reduction width of the sintered ore reduction pulverization index, which was derived from the results of the actual furnace use test.

Furthermore, FIG. 2 shows the relationship between the level of differential pressure used in Example 2 and the reduction range of the sintered ore reduction powdering index, which was also derived from the results of the actual furnace use test.

The standard value for the length of the low-temperature heat storage zone is Om, the standard value for the differential pressure of the static pressure at the furnace wall is QOg/cd, and when the length of the low-temperature heat storage zone returns to Om, and/or the furnace wall When the differential pressure of the partial static pressure exceeds GOg/c-, the reduction pulverization index of the sintered ore is gradually increased.

(Effect of the invention) Below 1. As explained in , in the present invention, by using highly reactive coke, gas utilization efficiency can be increased and blast furnace operation can be performed with a small coke ratio.

In addition, even if the temperature of the heat storage zone is lowered, it is possible to implement measures to suppress poor ventilation and ensure a stable gas flow.
It is also possible to increase shaft efficiency. In this way, according to the present invention, the productivity of blast furnace operation can be improved.

[Brief explanation of the drawing]

Figure 1 is a chart showing the relationship between the length of the low-temperature thermal storage zone of 500 to 700°C and the decline in the sinter reduction pulverization index, measured by measuring the temperature distribution in the height direction inside the blast furnace using a vertical sonde. Figure 2 is a chart showing the relationship between the differential pressure and the reduction width of the sintered ore reduction pulverization index by measuring the static pressure at the furnace wall.

Claims (1)

[Claims] When operating a blast furnace with highly reactive coke with a JIS reactivity of 30% or more, the pressure distribution and/or temperature distribution in the height direction within the blast furnace is measured, and the differential pressure and/or temperature distribution at each stage is measured.
Or a blast furnace operating method characterized by adjusting the reduction pulverization index of sintered ore so that the temperature becomes a reference value.