JPH0776369B2 - Blast furnace scale-down operation method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a scaled down operation method of a blast furnace capable of lowering a charge level in a short time.

[Prior Art] In recent years, the life of blast furnaces has greatly increased due to the progress of equipment technology and operation technology, and many large blast furnaces that have been operating for more than 10 years have been found. However, it is often seen that the lining thickness of the lower part of the shaft and the bosh section decreases gradually with the number of years of operation, which causes an increase in the fuel ratio and a deterioration in productivity. As a countermeasure, a method has been implemented, in which the charge level in the blast furnace is lowered to a predetermined level, the air is blown off, and the irregularly shaped refractory is sprayed and repaired from the inside of the furnace.

Generally, the scale reduction operation method of a blast furnace is to stop the charging of raw materials from the furnace top, burn the coke with the high temperature air blown from the tuyere, and lower the charging level to the tuyere level (scale reduction). To do. Since the B gas generated during the reduction operation becomes hotter as the reduction operation proceeds, water is sprayed from the furnace top to protect the equipment. As the scale is reduced, the amount of air blown is gradually reduced, and when the charge level reaches a predetermined level, the air is blown off.

[Problems to be solved by the invention] Fig. 2 shows a conventional scale-down operation example (implemented in a 4,000 m ³ class blast furnace). Stock line level (charge level) 20 m
It takes about 23 hours to reach. To increase the speed of scale reduction, it is sufficient to maintain a high air flow rate,
There is a limit because the furnace top gas temperature rises excessively and causes problems such as damage to the charging device. In this example, in order to maintain the furnace top gas temperature at 500 ° C. or lower, the air flow rate is reduced to 1/2 and 100 T / h of sprinkling cooling is performed from the furnace top.

It is an object of the present invention to provide a scale reduction method that can reduce the time required for scale reduction.

[Means for Solving the Problems] The present invention is intended to achieve the above-mentioned object, and the blast furnace is performed while water is sprinkled from the top of the furnace while the coke ratio is increased stepwise and the air flow rate is decreased stepwise. In the reduced scale operation method of, the ratio of added oxygen to the air flow of all tuyeres is increased stepwise and the amount of water sprinkled from the furnace top is controlled so that the gas temperature at the furnace top does not exceed a certain temperature. is there.

[Action] Oxygen-enriched air blast reduces the speed of reduction by about twice as much as before.
The time required for scale reduction is greatly reduced. Moreover, since the amount of generated gas is reduced, the amount of sprinkling water for cooling can be reduced. The gas temperature at the furnace top is a certain temperature or higher, and this temperature needs to be changed depending on the arrangement of the equipment at the furnace top.
Since the blast furnace is reduced in scale so that the temperature does not exceed 500 ° C, the function of the furnace top equipment will not deteriorate and damage due to burning will not occur.

[Examples] Examples of the present invention will be described in detail below. FIG. 3 is a vertical cross-sectional view showing a state in which blast furnace is scaled down. Reference numeral 1 is a furnace top, 2 is a stock line for charging, 3 is a tuyere, 4 is a conduit for supplying hot air or the like to the tuyere, and 5 is a sprinkling pipe for cooling the gas generated in the furnace. The blast furnace scale down blowing is generally performed as follows. First, increase the charging of coke,
After that, charging of raw materials is stopped. The stock line level 2 is gradually lowered while blowing hot air from the tuyere 3 through the conduit 4. At this time, the temperature of the furnace top 1 rises when the air flow rate is gradually reduced in accordance with the descent of the stock line level 2 to lower the stock line level 2. Therefore, in order to suppress the temperature rise, Multiple sprinklers 5 provided
Water is sprinkled from it to cool the gas temperature. In such a process, oxygen enriched blast is performed for all tuyere of the present invention,
Moreover, the ratio of the added oxygen to the amount of air blown from the tuyere is changed to blow air. FIG. 1 shows the method of the present invention the same as FIG.
It is a graph showing the transition of operating specifications when implemented in a 4,000 m ³ class blast furnace. Two hours after starting the scale reduction, the coke ratio was increased to 600 kg / Tpig, the air flow rate was changed to 4,000 m ³ and the added oxygen amount was changed to 500 m ³ , and this state was maintained for 4 hours.
The stock line was lowered to 12m. After 6 hours, the coke ratio was increased to 700 kg / Tpig, the air flow rate was changed to 1,500 m ³ , and the added oxygen amount was changed to 750 m ² , and this state was maintained for 9 hours.
The stock line was lowered to 20m. After that, the ventilation was stopped and the scale reduction was completed. During this time, the amount of water sprinkled from the furnace top should be 10T / H → 25T / H → so that the temperature of the furnace top gas does not exceed 500 ℃.
Increased to 50 T / H. This allowed the furnace top gas temperature to be kept below 500 ° C, and there was no damage to the charging equipment. The time required to reduce to 20 m by the method of the present invention is 1
It was 5 hours.

The results of the conventional scale reduction method and the scale reduction method of the present invention are shown in Table 1.

From this table, the time required for scale reduction is reduced by 8 hours compared to the conventional method, the average coke ratio can be reduced by 20 kg / T, and the total sprinkling volume is 60%.
You can see that it has decreased.

[Effect of the Invention] Since the present invention performs reduced-scale air-blowing by oxygen-enriched air blowing, the time required for reduced-scale can be significantly shortened compared to the conventional method, and the production reduction amount for intermediate furnace wall repair performed can be reduced. Less. Further, since the gas generation amount is reduced, the sprinkling amount for cooling can be significantly reduced. The effect is that the average coke ratio can be smaller than in the conventional case.

[Brief description of drawings]

FIG. 1 is a graph showing the transition of operational specifications when the method of the present invention is carried out in an actual furnace, and FIG. 2 is a graph showing the transition of operational specifications when the conventional method is carried out in an actual furnace, FIG. [Fig. 3] is a vertical cross-sectional view showing a state in which blast furnace is reduced in size. 1 ... Furnace top, 2 ... Charge stock line, 3 ... Tuyere, 4 ... Hot air conduit, 5 ... Sprinkler pipe.

Claims (1)

[Claims] Claim: What is claimed is: 1. In a blast furnace scale-down operation method in which the coke ratio is increased stepwise and the air flow rate is decreased stepwise, while sprinkling water from the top of the furnace, the ratio of added oxygen to the air flow rate of all tuyeres. And the amount of water sprinkled from the furnace top is controlled so that the gas temperature at the furnace top does not rise above a certain temperature.