JPS58100604A - Operating method for blowing-down of blast furnace - Google Patents

Abstract

PURPOSE:To prevent the blowing-by at the end period in the operation for reduction of the stock line and to reduce the time for reduction of the stock line in the stage of reduction of the stock line and blowing out of a blast furnace by blowing air enriched with oxygen through tuyeres, a tap hole, etc. CONSTITUTION:In the operation for reduction of the stock line and blowing out of a blast furnace to reline the same, blowing-by arises in some cases at the end part of the reduction of the stock line during blowing out and in the top part of the blast furnace, explosion accidents arise, resulting in the failure of furnace top equipment. In order to prevent such accidents, the rate of blasting to the inside of the furnace is required to be decreased and in order to prevent the consequent decrease in the rate of combustion of coke, oxygen-enriched air is fed through tuyeres and a tap hole or through a tentative tap hole. Thus, the fuel coke at the tuyere ends is decomposed thoroughly to CO by CO2. The air is fed by controlling its flow rate at the rate lower than the limit rate of blasting in order to increase the rate of combustion of coke and to prevent the generation of blowing-by, whereby the decrease in the descending speed of the stock line is prevented and the time for the reduction of the stock line is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention proposes a method for reducing the blast furnace air flow rate and shortening the downscaling time in order to prevent blow-through when performing a downscaling operation of a blast furnace.

Reduced-scale blowdown operation of a blast furnace refers to replacing the contents in the furnace with all-wax coke, ballast, etc. for blast furnace renovation etc., burning the contents in the furnace to lower the acreage reduction level, and stopping the blast furnace operation. However, in this reduced-scale blowdown operation, the most important thing to be aware of is that the combustion gas, which is mainly composed of O and gas, blown into the blast furnace blows unburned to the upper part of the blast furnace and enters the inside of the furnace. The purpose of preventing the occurrence of the phenomenon of blowing up the contents, that is, the atrium. When a phenomenon occurs in this atrium, #I 0. The gas has a high concentration of CO1 in the upper part of the blast furnace.
This is because it can get mixed into H, gas, trigger an explosion, and lead to a major accident with damage to the furnace body and furnace equipment. Furthermore, at the end of vellum reduction, the combustion gas blown in from a separate port flows intensively on the furnace wall side, so this phenomenon is particularly likely to occur in the atrium.

In order to prevent this blow-through phenomenon, it is necessary to reduce the flow rate of combustion gas blown into the blast furnace as the scale reduction level is lowered, and it is necessary to maintain a particularly low draft level at the end of the scale reduction stage. Figure 1 shows the blast furnace air flow rate at the final stage of acreage reduction on the horizontal axis, the blowout failure (pressure loss/burden load) on the vertical axis, and the relationship between the two under three furnace top pressure conditions (0 (Tsukuda,
0.1/ffl, 1.5-7-i), and is a graph for determining the limit air flow rate at the end of scale reduction. From this graph, for example, when the furnace top pressure is 1.51-, the limit air flow rate is It can be seen that this is very low, less than 100ON11/min. Furthermore, Figure 2 is a graph showing the transition of top gas components during reduced scale blowdown operation. Because of the combustion in the CO gas tank, the amount of exhaust gas is higher in the CO gas tank than in the CO gas tank. Therefore, at the end of the reduction stage, the amount of coke burnt decreases, so the rate of descent of the reduction level becomes extremely slow, resulting in a significant extension of the reduction time. Fig. fJ3 is a graph showing changes in the air flow rate and the reduction level during the reduction blowing operation, and it clearly shows the above-mentioned situation.

The present invention was made in view of certain circumstances, and reduces the blast furnace air flow rate in order to prevent blow-through at the end of the scale reduction stage of the blast furnace blowdown operation, and also prevents a decrease in the rate of descent of the scale reduction level. The purpose is to shorten the scale reduction time.

The blast furnace blowdown operation method according to the present invention is characterized in that air enriched with oxygen is blown through the tuyeres at the end of the scale reduction stage.

Similarly, at the end of the acreage reduction stage, while normal air or oxygen-enriched air is blown through the siding, normal air or oxygen-enriched air is blown through the taphole and/or temporary taphole. Features.

First, the principle of the present invention will be described. At the end of the downscaling phase of blast furnace blowdown operation, it is necessary to reduce the amount of air blown into the blast furnace in order to prevent the occurrence of blowdown, as described above, and as a result, the amount of coke burnt decreases. Blows air enriched with O and gas. By increasing the total 0° gas position during air blowing in this way, the following (1):
The temperature of the combustion zone at the tip of the tuyere increases due to the striking and significant exothermic reaction shown in equation (2).

o, + C= CO,...(1) C02+C=2CO+58.2kca//g-mo/
-・(2) Therefore, the fuel at the tip of the tuyere completely decomposes, increasing the amount of coke burnt, and blowing air at a level below the limit fan to prevent blow-by, and also to prevent a decrease in the descending speed at the reduced scale level. It is possible to shorten the scale reduction time. Note that the time when the air enriched with O gas starts to be blown is the time when the falling speed of the acreage reduction level slows down, that is, the reduction level reaches a position of about 5 sg above the tuyere, and the inside of the furnace above the tuyere level is reached. This is from the time when almost all lines were filled with coke.

Also, at the end of scale reduction, 0. Another way to increase the gas total is to increase the acreage reduction level to about 5#111 above the tuyere.
! From the time when the contents of the furnace above the grain level became almost completely coke, normal air or oxygen was enriched from the taphole and/or temporary tapholes such as the U-residue extraction hole. One possibility is to blow air. In this case as well, for the same reasons as in the above case, it is possible to shorten the reduction time, burn coke below the tuyere level, and lower the reduction end level below the tuyere. Therefore, it is possible to reduce the amount of content to be scraped out from inside the blast furnace after completion of scale reduction, and the number of man-hours for scraping out can be significantly reduced.

Furthermore, after the residual pig iron removal is completed, the air is heated to approximately 900°C.
) to cold air (approximately 100°C) K, it is possible to accelerate the temperature reduction of the contents in the furnace, and it is also possible to significantly reduce the number of man-hours required for cooling the contents.

Next, examples of the method of the present invention will be explained. Figure 4 shows
This is a graph showing the effect of shortening the reduction time by the method of the present invention in the reduced-scale blowdown operation of a blast furnace, with the horizontal axis representing the reduced-scale blowdown operation time, and the vertical axis representing the air flow rate and the reduction level. The case using the method of the present invention (solid line) is compared with the case using the conventional method (solid line).
This is shown in comparison with the one-dot chain line). As shown in the figure, in the case of the method of the present invention, from the time T when the area above the tuyere is almost entirely coke (the level of reduction corresponds to the position of about 5 baits above the tuyere), air: 62ONII//min. 0.
Gas: 23ON-//min and 0. Although gas-enriched air was blown, the reduction time was significantly reduced to 5 hours compared to the conventional method.

In this example, air enriched with O and gas is blown not only from the tuyere but also from the taphole and the residue extraction port.
A method of burning coke below the tuyere level to reduce the amount of material scraped out of the blast furnace and the number of man-hours required for scraping out the blast furnace, and a method of switching the blowing air from hot air to cold air after the removal of residual pig iron is completed. It was also shown that the total number of man-hours required for blast furnace renovation would be significantly reduced.

As detailed above, the present invention is directed to blowing oxygen-enriched air from the tuyere and/or blowing ordinary air or oxygen-quaternized air at the end of the reduction stage of the reduced-scale blowdown operation of a blast furnace. By blowing air from the taphole, etc., the O
! Since the total amount of gas is increased and the amount of coke combustion is increased, it is possible to suppress the air blowing amount to less than the limit air blowing amount in order to prevent the occurrence of blow-by, and to significantly shorten the reduction time.

Therefore, the present invention has a significant effect on reducing the number of man-hours required for blast furnace blowdown operations performed during blast furnace renovation.

[Brief explanation of the drawing]

Figure 1 is a graph for determining the critical air flow rate at the end of scale reduction.
Figure vJ2 is a graph showing changes in top gas components during reduced-scale blowdown operation, Figure 3 is a graph showing changes in air flow rate and reduction level during reduced-scale blowdown operation, and Figure 4 is a graph showing the method of the present invention. It is a graph showing the shortening effect of acreage reduction time by. Patent applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Noboru Kono 0 1000 2000 3Fish air blast t (NmV min) Calculation 1 Figure 0 6 12 18
24 hours (HRL) 2 hours (HRL Mushroom 3)

Claims (1)

[Claims] 1. In the reduced scale blowdown operation of a blast furnace, #
A blast furnace blowing operation method that involves blowing air enriched with minerals through the tuyeres. 2. Blast furnace blowdown operation characterized by blowing normal air or oxygen-enriched air from the taphole and/or temporary taphole at the end of the downscaling stage in the blast furnace blowdown operation. Method. 8. In the blast furnace reduced-scale blowdown operation, at the end of the scale reduction stage, oxygen-enriched air is blown through the tuyeres, and normal air or oxygen-enriched air is blown through the taphole and/or temporary outlet. A blast furnace blowdown operation method characterized by blowing air from the pigtail hole.