JPH02200711A - Method for operating blast furnace - Google Patents

Abstract

PURPOSE:To produce molten iron at low coke ratio and good productivity by replacing a part or the whole of the coke for metallurgy with the coke improving the reactivity and adjusting furnace heat in height direction of a blast furnace at the time of operating the blast furnace. CONSTITUTION:As the coke charged from the furnace top in the blast furnace, a part or the whole of the coke is used by replacing with the high reactive coke having >=30% JIS reactivity, which is produced by blending high reactive non-caking coal with the general raw coal as the raw coal or blending a little quantity of lime stone, iron ore and alkali kind. In this case, heat holding zone temp. in the height direction in the furnace is detected with vertical sonde, etc., and by executing furnace temp. adjustment according to the difference of the detected temp. to the reference value, variation of the furnace heat is prevented, and by improving the utilizing ratio of CO gas, the molten iron is produced at the low coke ratio and the good productivity.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention improves productivity by using highly reactive coke 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 top of the furnace, and after this iron ore is pre-reduced in the furnace,
Hot metal is produced by reducing and melting it to a metallic state. At this time, in order to improve the reduction efficiency of iron ore,
Publication No. 169 discloses that iron ore and small coke are mixed in advance, and this mixture and normal coke are charged in a layered manner.

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.

(Problems to be solved and attempted 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. is used. 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 point at which reduction equilibrium is reached does not change, so the shaft efficiency, indirect reduction rate, and CO gas utilization rate also increase. It does not improve beyond the value.

In addition, the temperature in the height direction inside the blast furnace is measured by a vertical sonde as disclosed in Japanese Patent Application Laid-Open No. 59-16917, but when coke with low reactivity is charged, the heat storage zone temperature Since it is around 1000°C and does not change, it is not used as a management index for adjusting furnace heat.

Therefore, the purpose of the present invention is to increase the reactivity of coke charged into a blast furnace, lower the heat storage zone temperature, promote the reduction reaction of iron ore, and produce hot metal with high productivity. shall be.

(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 with highly reactive coke of 0% or more charged into a blast furnace, the temperature of the thermal storage zone in the height direction inside the blast furnace is detected, and the furnace heat of the blast furnace is adjusted according to the difference between the detected temperature and the standard value. It is characterized by carrying out adjustment.

First, we will discuss highly reactive coke.

The highly reactive coke used in the present invention is JISK 21
J' when measured by the reactivity test method of 51-1977.
It is necessary that the lS reactivity is 30% or more.

The numerical limitation of 30% is based on the fact that, as shown in Japanese Patent Application No. 193457/1982, 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 per unit weight of coke increases, and the proportion contributing to the reaction increases. On the other hand, the particle size is 15
When the temperature is exceeded, the ratio of the inside of the coke to be effectively utilized for the gasification reaction decreases.

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 approximately the same as that of normal coke. It is preferable to maintain strength that does not deteriorate when high reactivity occurs.

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, limestone, which acts as a catalyst to promote reactions,
Small amounts of iron ore and alkalis are also added to coking coal.

Since this highly reactive coke has high reactivity, the interfacial reaction in which 002 in the furnace comes into contact with the coke surface and turns into CO takes place 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+C02→2CO 2 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 thermal reserve zone of about 1000 degrees Celsius is generated, and its value hardly changes, whereas
By using highly reactive coke it is possible to reduce the temperature of the thermal storage zone to 900-950°C.

As a result, there is more room at the reduction equilibrium point, so reduction progresses further, and coke gasification progresses at a lower temperature, producing a larger amount of CO gas than before, which improves shaft efficiency and indirect The reduction rate and CO gas utilization rate are improved, and since indirect reduction is an exothermic reaction, the coke ratio can be lowered.

Next, we will discuss the furnace heat adjustment by detecting the heat storage zone temperature.

By using highly reactive coke, the heat reserve zone temperature is reduced to 900-950°C, but since that value changes, the amount of coke ratio that can be reduced depending on the value of the heat reserve zone temperature is different.

Therefore, unless the furnace heat is adjusted, furnace heat fluctuations will occur, the effects of highly reactive coke cannot be maximized, and high productivity cannot be ensured.

In the present invention, the temperature of the heat storage zone is detected by a vertical sonde, etc., and the furnace heat is adjusted according to the difference between the detected temperature and the reference value, thereby preventing fluctuations in the furnace heat and performing stable blast furnace operation. be able to.

For the relationship between the value of the heat reserve zone degree and the coke ratio that can be reduced, the results of an offline experiment may be used, or the results of a furnace use test may be used.

In addition, the method of adjusting the furnace heat is generally to change the coke ratio (ratio of iron ore and coke charged from the top of the furnace, hereinafter abbreviated as O/C), but the It is also possible to use changes in temperature, amount of added moisture, and amount of pulverized coal injected.

(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 3,000 rrr, and in the conventional method, iron ore and regular coke are charged from the top of the furnace at a ratio of 0/C-3.2, and the immediate flame temperature is set to 2,270°C (
Hot metal was produced while maintaining the hot air temperature at 1100° C., added moisture at 35 g/N (no pulverized coal injection) (Comparative Example 2).

In Example 1, 15% of the normal coke was JIS reactivity 3.
5%, highly reactive coke with a particle size of 15 mm, the highly reactive coke is mixed with iron ore and charged, and the temperature of the thermal storage zone is detected by a vertical sonde, and the reference value of the detected temperature is 1.
The results are shown in which the coke ratio (0/C) was changed according to the difference with respect to 000°C.

In Example 2, the entire amount of normal coke was replaced with JIS 15 Reactivity 30 highly reactive coke, the highly reactive coke was charged with iron ore in a layered manner, and the temperature of the thermal storage zone was detected by a vertical sonde. The results are shown in which the coke ratio, hot air temperature, and added moisture amount were changed according to the difference in detected temperature from the standard value of 1000°C.

In Example 3, 15% of the normal coke was JIS reactivity 35.
%, particle size of 15%, and the highly reactive coke is mixed with iron ore and normal coke in 1/2 ratio and charged, and the temperature of the thermal storage zone is detected by a vertical sonde. The results are shown in which the amount of pulverized coal injected was changed according to the difference in temperature from the standard value of 1000°C.

Both Examples 1 and 2.3 achieved a reduction in coke ratio compared to Comparative Example 2.

Note that Comparative Example 1 is the same as Example 1 without detecting the heat storage zone temperature using a vertical sonde, and compared to Example 1, the degree of decrease in the coke ratio is smaller, and the hot metal temperature and hot metal [S1] are also lower. Blast furnace operation is not efficient.

Figure 1 shows the relationship between the value of the heat storage zone temperature determined by off-line experiments and the coke ratio that can be reduced. Actions were taken to change the amount of pulverized coal injection.

The standard value is 1000°C.

(Effects of the Invention) As explained above, 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.

Furthermore, since the temperature of the heat storage zone can be lowered and the operation can be performed at a coke ratio commensurate with the decrease, it is also possible to increase shaft efficiency. In accordance with the present invention, the productivity of blast furnace operation can be improved.

[Brief explanation of the drawing]

FIG. 1 is a chart showing the relationship between the heat storage zone temperature, the coke ratio that can be reduced, and the amount of pulverized coal that can be reduced. Agent Patent Attorney Tatsuo Chanoki 11JC
”C.J.

Claims (1)

[Claims] When high-reactivity coke with a JIS reactivity of 30% or more is charged into a blast furnace and operated, the temperature of the heat storage zone in the height direction inside the blast furnace is detected, and according to the difference between the detected temperature and the standard value, A blast furnace operating method characterized by carrying out furnace heat adjustment of a blast furnace.