JPH0280503A - Method for operating blast furnace - Google Patents

Abstract

PURPOSE:To smoothly start up blast furnace operation without increasing fuel ratio and worsening the furnace condition by restarting blast after directly heating and raising the temp. in the furnace core part at the time of stopping or reducing the blast. CONSTITUTION:At the time of stopping or reducing the blast intentionally or unexpectively the blast in the resumed after heating and raising the temp. The furnace core part, heating is executed by blowing oxygen gas, coke powder, etc., with a lance toward the furnace core part through a tuyere, or by contacting an electrode with the furnace core part, etc. By this method, the blasting and the blast stopping into the blast furnace is optionally selected and the operational condition of the blast furnace can be intentionally changed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method of operating a blast furnace, and particularly to a method of operating a blast furnace in which the furnace core is directly heated to raise the temperature before starting air blowing after air suspension or air reduction.

(Prior Art) Blast furnaces for steelmaking can produce large quantities of pig iron, and they have excellent performance and are well controlled, and have reached the point where nothing better can be done.

However, in general, the more sophisticated the device, the more sensitive it will be to react to even slight changes in operating conditions.

Furthermore, blast furnaces are basically operated continuously for 24 hours, and scheduled wind breaks of 20 to 30 hours are carried out once or twice a month for maintenance and production adjustments.

However, considering the future labor situation, the simultaneous closure of steel mills is being considered in order to shorten working hours, and the need to temporarily stop blast furnace operations is becoming more necessary than ever. ing.

Conventionally, when a blast furnace is shut down, in order to compensate for the heat dissipated during that period, the fuel ratio is increased immediately before the wind shutdown and for several days after the blast furnace starts up to prevent a drop in furnace heat.

Therefore, the loss in energy costs is large, and it has been thought that temporary blast furnace blast furnaces are not necessarily economical.

In addition, in order to have a long wind break, the ore/coke ratio of the charging material should be drastically lowered, and no material should be charged before the wind break, and the charging level should be lowered to a maximum of just above the tuyere. The method was to reduce the size and take a break.

As mentioned above, when the air is stopped in a planned manner, the fuel ratio is increased in advance to raise the furnace heat and the operation is performed on the safe side, so even after the air is blown, the furnace can be started up relatively smoothly.

However, if there is a sudden wind stoppage or wind reduction due to equipment trouble, etc., the operation is often not stabilized until the wind blowing starts and the wind is turned on because the ore/coke ratio of the charging material is still high.

In other words, since the blast furnace is suddenly shut down without sufficient preparations such as increasing the fuel ratio, the furnace heat decreases due to heat dissipation, worsening the permeability of gas in the blast furnace, and even when air is blown, the furnace heat decreases. Because the gas flow within the blast furnace is not stable, the reaction proceeds unevenly, resulting in poor furnace conditions.

Furthermore, since blast furnaces do not have sufficient production flexibility, furnace conditions tend to worsen, especially when the iron output ratio is low.

However, when the blast furnace is shut down for production adjustment, it is necessary to increase the fuel ratio each time, which is not necessarily economical.

(Problem to be Solved by the Invention) The furnace core of a blast furnace is made of lump coke, and while the charge passes through the furnace in a few hours, it is estimated that it takes several days for the lump coke to be replaced. ing.

However, when the wind is suspended or reduced, the temperature of the furnace core gradually decreases due to heat dissipation to the outside.

Even if the blowing condition is increased, for example, the blowing temperature is increased, or the blowing moisture or pulverized coal is adjusted, the blowing air does not reach the inside of the furnace core and the furnace core becomes cold. Moreover, even if the coke ratio of the charging material is increased after blowing air, it will take a considerable amount of time for the charging material in the furnace to be replaced, so it will not be effective immediately, and before recovery, the permeability will deteriorate and the circumference will increase. In many cases, the balance would collapse and the furnace condition would become extremely unstable.

(Means for Solving the Problems) This invention solves the above-mentioned difficulties in the present invention, and in the operation of a blast furnace, when there is a planned or sudden wind suspension or wind reduction without increasing the fuel ratio, This is a blast furnace operating method characterized by restarting air blowing after directly heating the furnace core.

Since the present invention, it has been proposed to use a plasma generator as a method of increasing the blast temperature for the purpose of increasing the production volume of blast furnaces. (For example, outside of JP-A-61-199006) However, this method increases the temperature of the blown air, and is not effective if the ventilation of the furnace core deteriorates. The technical idea of the invention is different in that it does not heat.

In addition, as a heating means in the present invention, oxygen gas, oxygen-enriched air, compressed air, or these heated gases and combustible gases burned by these, fuels such as coke powder are directed toward the furnace core using tuyeres. lance blowing or by bringing the electrode into contact with the furnace core to perform resistance heating,
The temperature is raised by induction heating, plasma arc heating, etc. Of course, it is also possible to combine two or more of these.

It is easiest to insert the electrodes and herans for heating the furnace core through the tuyere, but it is also possible to install the insertion port from a specific position other than the tuyere and insert it into an appropriate location.

When inserting from the side, 2000~
It is necessary to pass through a raceway section at a temperature of 2400° C., and since the air is blown at a high pressure, it is extremely difficult to seal the hot air gas from blowing out due to equipment considerations. Therefore, it is an important point of the present invention to carry out the heating operation in a state where the wind is suspended or reduced.

In order to measure the temperature of the furnace core, a furnace core temperature probe consisting of an optical fiber and a two-color thermometer may be inserted through the tuyere. Unexamined Japanese Patent Publication No. 61-2574 for the purpose of measurement while blowing air
Although various core probes such as No. 05 have already been proposed, since the present invention performs measurements during wind rest or reduced wind, non-water-cooled simple temperature probes can also be used.

Although the temperature of the furnace core is not necessarily required, it is desirable to use it as a furnace heat index for heating control. In the following explanation, the coke temperature at a portion inserted 2.5 m from the tip of the tuyere will be used as the furnace core temperature.

Figure 1 shows various heating patterns for the furnace core.

Figure 1 (a) shows pattern A when the furnace core heating operation is performed at the end of the wind break, (b) shows pattern B when the furnace core heating operation is performed at the beginning of the wind shutdown, and (c) shows pattern C when the furnace core heating operation is performed at the beginning of the wind shutdown. When heating first at the beginning of the wind break and heating for adjustment at the end, (d)
When heating operation is repeated periodically in pattern D, (e
) is a case where heating is always carried out using the radiated heat in pattern E when there is no wind.

The same effect can be obtained even if the above-mentioned wind suspension is replaced with a sudden wind reduction operation.

Various heating patterns other than these can be considered, but it is necessary that the furnace core temperature be heated to a specified value or higher before the start of air blowing.

The specified value cannot be set arbitrarily, but should be appropriately determined for each blast furnace depending on the furnace capacity, operation mode, etc. of the blast furnace.

When there is a planned wind break, the duration of the break is known, so it is possible to set the heating pattern in advance according to the downtime, but if there is a sudden wind break or wind reduction,
Since it is difficult to estimate the recovery time, it is desirable to raise the temperature immediately before blowing air as in pattern A, or to raise the temperature periodically as in pattern D so as not to cool the furnace core too much.

(Example) The present invention will be specifically described below using an example in which a blast furnace with an internal volume of 3,880 m3 was intentionally shut down for 24 hours.

To stop blowing air while maintaining normal operation without increasing the fuel ratio before shutting down the blast furnace. Pattern (A) in Figure 1 was adopted because the wind down time was relatively short at 24 hours.

Maintenance of the furnace body, including replacing the seal valve of the furnace top hopper and the charging chute, took approximately 23 hours.

As a result of continuously measuring the furnace core temperature during this period, it was found that 1
The temperature had dropped from 310°C to 1230°C after 23 hours.

Therefore, as shown in FIG. 2, temperature-raising lances 1 were inserted from four tuyeres evenly in the circumferential direction to positions 3 m from the tips of the tuyeres using the insertion cart 2. The temperature raising lance l had a non-water-cooled double-tube structure, and had a burner structure in which COG gas was supplied from the inner tube with compressed air enriched with 30% oxygen from the outer tube and burned at the tip.

The amount of combustion air was adjusted so that C0Gfi was 400 Nm'/hr and the air ratio was 1.2. After continuing this type of furnace core heating during summer time, the furnace core temperature was measured and found to be 1230.
It was detected that the temperature had dropped to 1,350°C, so the four temperature-raising lances 1 were pulled out, and 24 hours later, air blowing was resumed as planned, allowing stable operation to be maintained.

If separate tuyeres are used for measurement and heating, the core temperature can be detected continuously during the heating process, and various heating patterns are possible.

In addition, if the heating temperature is delayed, the COG flow rate is increased to control the heat input, and the furnace core temperature reaches 1300℃ at the scheduled time.
I made it as above.

(Effects of the Invention) According to the present invention, the blast furnace ventilation and ventilation can be arbitrarily selected, which is extremely effective. In other words, there is no problem of a large increase in the fuel ratio due to wind breaks as in the past, the production schedule can be changed arbitrarily according to the labor force, and the operational form of the blast furnace can be changed economically in advance. It is excellent. In addition, in the event of wind suspension or reduction due to sudden trouble, necessary measures can be taken immediately, and blast furnace operations can be restarted smoothly without deteriorating furnace conditions.

[Brief explanation of the drawing]

Figures 1 (a), (b), (c), (d) and (e) are explanatory diagrams of temperature increase patterns of furnace core heating according to the present invention, and Figure 2 is a diagram showing an example of furnace core heating. ■・・・Temperature raising lance 2・・・Drawing of the insertion trolley No.

Claims (1)

[Claims] Blast furnace operation characterized by restarting air blowing after directly heating the furnace core to raise its temperature when the wind is stopped or reduced either intentionally or suddenly without increasing the fuel ratio during blast furnace operation. Method