JPH01222004A - Method for operating blast furnace - Google Patents

Abstract

PURPOSE:To smoothen starting-up operation after stopping blast by beforehand lowering charged material level in a blast furnace to bosh level in the furnace before stopping the blast and starting to the blast-stopping period by making the remained material in the furnace only coke and flux for adjusting slag component. CONSTITUTION:The coke and flux 2 are charged into the furnace on the charged material 1 by necessary quantities and after that, the charge is stopped, to lower the level of the charged material 1. When the level of the coke and flux 2 reaches to the aimed level in the both part of the blast furnace, it is started in blast-stopping period. Then, the remaining material in the furnace becomes only the coke and flux 2. After stopping the blast, the tuyere 3 is closed and left as it is. By this method, the starting-up operation after blast-stopping period, can be smoothened.

Description

[Detailed description of the invention] [Industrial use! )]

The present invention relates to an operating method for smoothly starting up after a blast furnace by reducing the scale when the blast furnace enters a long-term wind shutdown.

[Conventional technology]

Conventionally, when a blast furnace is to be closed for a long time of 100 hours or more, an operating method is used that takes into account the following points. ■ Ensuring the hot metal temperature when entering the body air ■ Preventing the melting of the charge remaining in the furnace during wind breaks ■ Preventing solidification of the pig iron slag remaining at the bottom of the furnace ■ Preventing the rapid dissolution of iron ore remaining in the furnace during start-up The above points In consideration of the By stopping the process while keeping the amount of hot metal produced per coke 11 (coke ratio) low, it has been possible to smooth the start-up during long periods of wind downtime.

[Problem to be solved by the invention]

However, the above conventional method has encountered the following problems. ■ During the wind break, residual iron in the furnace dissolves. ■ When the residual iron in the furnace melts, low-temperature hot metal drips to the bottom of the furnace, lowering the temperature of the hot metal at the bottom of the furnace. ■ When the hot metal generated during melting during wind rest falls through the residue in the furnace, it solidifies midway due to the influence of the residue in the furnace.
There is a high possibility that deposits or lumps will form which will be an obstacle during start-up. ■ At a very critical stage immediately after start-up, residual iron in the furnace rapidly dissolves in the lower part of the furnace, that is, near the tuyere, causing the tuyere to close. ■ The low-temperature hot metal generated in the furnace at the beginning of startup flows into the bottom of the furnace, where the temperature is still low, which causes the temperature at the bottom of the furnace to drop rapidly, making it difficult to discharge the residual pig iron slag from the furnace, and causing a drop in the temperature at the start-up of the furnace. Early recovery becomes difficult. This invention was made in order to solve these conventional problems, and aims to propose an operating method that can smoothly and quickly start up after a long period of wind cessation. .

[Means to solve the problem]

The gist of this invention is to reduce the charge level in the blast furnace to the Bosch level at the bottom of the blast furnace in advance before the blast furnace is put into a long-term air break, and to reduce the remaining amount in the furnace to only coke and flux for adjusting slag components. It is characterized by entering a period of rest.

[For production]

In this invention, the reason why the level of the contents in the furnace is reduced to the Bosch level at the bottom of the blast furnace is to prevent as much melted material from remaining in the furnace during air rest. However, the level of the charge must be at the top of the tuyere to avoid a blockage condition. Furthermore, the reason why the only residues in the furnace before the wind break were coke and slag adjustment flux was to eliminate any iron content that would be a problem due to melting during the wind break. The present invention will be explained below based on the drawings. Figure 1 (A> shows the contents in the furnace and their levels before the scale reduction operation, Figure 1 (B) shows the state immediately before the scale reduction operation, and Figure 1 (
C) is a diagram showing the state of contents in the furnace at the time of wind break. (3) in the figure is the tuyere. In other words, when transitioning from the normal operating state (Fig. 1 A) to reduced-scale operation, the contents in the furnace (coke + iron ore + flux) (1) are changed to (coke + flux) (2).
Charge the required amount of material (1), then stop charging and reduce the level of the material (1) in the furnace by adjusting the air flow rate, watering inside the furnace, etc.
Figure 1 B). When the level of the charge (2) reaches the target level (upper part of the tuyere) in the lower part of the blast furnace, that is, in the bosch section (Fig. 1C) through this scale reduction operation, a normal wind break begins. At this time, the residue in the furnace is (coke + flux) (2)
Only. After the wind breaks, immediately close the tuyere (3) to prevent air from entering, and leave it as it is. When the wind starts to rise after the wind has stopped, the closed tuyeres are sequentially opened and the charge level is restored (increased). (Example) The method of this invention was applied to the downsizing operation of blast furnace A (2700 m"). At that time, the level of the contents in the furnace was lowered to the Bosch area, and the residual material in the furnace was reduced to coke and 7 lac. Figure 2 shows the results of reduced scale operation when there was a long wind break.From Figure 2, even though the wind break was a long time of 105 hours and 50 minutes, the start-up operation was extremely slow. All went smoothly, and we were able to return to the normal air flow specifications in a short time of 22 hours and 35 minutes after blowing air.Incidentally, with the conventional method, if the air rest time was 100 hours or more, it would take about 48 hours to start up. [Effects of the Invention] As explained above, the method of this invention has the following effects: ■ As a result of reducing the melting of hot metal in the charge in the furnace during wind break, startup operation is possible. The generation of deposits and lumps that can be a nuisance to the furnace is extremely reduced, making start-up operations smoother after a wind break, and the start-up time can be significantly shortened. ■ The tuyere is blocked by residual iron in the furnace. ■ Since there is almost no possibility that the hot metal in the furnace flows into the bottom of the furnace and lowers the temperature at the bottom of the furnace in the early stages of start-up, it becomes easy to discharge the remaining iron slag from the furnace, and the operation can be improved. ■ It becomes possible to make large-scale equipment modifications to operating blast furnaces or adjust production volume by shutting down the blast furnace without significantly reducing production volume.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of this invention. Figure (A) shows the state where the charge is present up to the normal stock level before starting the reduction operation, and Figure (B) shows the furnace immediately before the reduction operation. Figure (C) is a diagram showing the state of the contents inside the furnace, and Figure (C) is a diagram showing the state of the contents inside the furnace at the time of wind break, and Fig. 2 is a diagram showing actual data of the scale reduction operation in an embodiment of the present invention. 1... Furnace contents (coke iron ore + 7 lux) 2... Furnace contents (coke + flags) 3...
Tuyere applicant Sumitomo Metal Industries, Ltd.

Claims (1)

[Claims] In the reduced-scale blowdown operation of a blast furnace, the level of the contents in the furnace is reduced to the blast furnace Bosch level before the wind is shut down, and the furnace enters the wind hiatus with only coke and flux for adjusting the slag components remaining in the furnace. How to operate a blast furnace.