JP2814506B2 - Slopping prediction method in smelting reduction. - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for predicting slotting in smelting reduction.

[Prior Art] One of the important factors in the smelting reduction of iron ore is the suppression of slopping. This sloping is a phenomenon in which slag, molten metal, and granular iron are spurted out of the reduction furnace in an abrupt manner.Slopping has a negative impact on production and hot metal production costs, such as shutdown of operations and reduction in iron yield. . For this reason, it is necessary to eliminate slotting.

By the way, suppression of sloping is also important in the operation of a converter, and research has been conducted on a method capable of accurately predicting the occurrence of sloping and quickly taking an action of the suppression. Conventionally, as a technique for predicting slopping in converters, a method of directly observing the fiber scope inside the furnace and predicting the slopping from the image (Yamane et al., Iron and Steel 71 (1985) S1045), and a method for predicting slopping obtained from exhaust gas information. A method of predicting slotting based on changes in carbon dioxide efficiency (Taki et al., Iron and Steel 74 (1988) S757) is known.

Among these, the former method inserts an optical fiber scope from the opening provided in the converter side, observes the inside of the furnace, views active slag foaming as a precursor phenomenon of slopping, and predicts slopping. . In the latter method, the decarbonation efficiency is continuously monitored, and a drop in the decarbonation efficiency is regarded as a precursor of the slopping, and the slopping prediction is performed.

[Problems to be solved by the invention]

However, such a method for predicting slopping in a converter cannot be applied to predicting slopping in a smelting reduction furnace for the following reasons.

That is, in the former method, it is assumed that the occurrence of sloping can be predicted about 40 seconds before that. However, in this time, the action for suppressing the sloping (reduction of the amount of acid supply, introduction of the foaming calming agent, Is not enough time to judge whether or not to take effect, and to take effect after implementing it.

In addition, in the smelting reduction method for continuous operation for a long time,
Observation holes in the furnace in which the fiberscope is inserted are often clogged due to long-term accumulation of slag, and maintenance is very difficult in a smelting reduction furnace having a closed structure for collecting generated gas.

In the latter method, the amount of gas generated in the smelting reduction is two to three times that of the converter (4 to 6 Nm ³ / min / ton in the converter, whereas 10 to 20 Nm ³ / min in the smelting reduction furnace). / ton) and high gas oxidation degree OD (converter OD: 0.05 ~ 0.1
On the other hand, it is difficult to monitor the decarbonation efficiency (DC / DO) as accurately as the converter in the smelting reduction furnace (about 0.4 to 0.7). In addition, even with this method, the occurrence of slotting can be predicted only about 40 seconds before that, and there is not enough time to take an action.

As described above, it is difficult to apply the slopping prediction technology conventionally used in converters to smelting reduction.

The present invention has been made in view of such a point, and an object of the present invention is to provide a method capable of accurately and sufficiently predicting the slotting in a smelting reduction furnace with a sufficient time margin.

[Means for solving the problem]

The present inventors have studied the phenomena in the furnace related to slopping, especially the behavior of slag in smelting reduction,
As a result, it was found that the slag formed just before the slopping, and that the slag surface gradually rises in the furnace height direction.

The present invention utilizes such a phenomenon to predict slotting.At a constant flow rate, gas flows into the furnace from gas purge holes provided in the furnace wall above the slag surface level during normal operation. The supply is performed, and the occurrence of slotping is predicted based on the pressure change on the gas supply side. That is, when the slag surface rises as a pre-slope step, the slag gradually fills the gas purge holes, and as a result, the pressure on the gas supply side increases. Therefore, by monitoring such a pressure change, it is possible to predict the slotting.

As a specific method of predicting the slotting by the gas pressure change, a reference value (threshold) of the pressure is set, and the occurrence of the slotping is predicted based on the fact that the pressure on the gas supply side exceeds this pressure. Can be generally adopted.

A plurality of gas purge holes can be provided at intervals in the furnace height direction, and by doing so, a slag surface rise can be detected more reliably.

The supply of gas from the gas purge hole is set to a dynamic pressure at which the gas purge hole is clogged by slag.

According to the present invention, as long as an appropriate reference value is set, the occurrence of sloping can be accurately predicted one to two minutes before the sloping, and the sloping suppression action is performed with a sufficient margin. be able to.

The present invention can be applied not only to iron ore but also to smelting reduction of Cr ore.

〔Example〕

FIG. 1 shows an embodiment of the present invention, wherein (1) is a smelting reduction furnace, (2) is a top blowing lance, (3) is a side blowing tuyere,
(4) is a bottom blowing tuyere, ore, carbonaceous material, and flux are charged from the upper part of the furnace, stirring gas is supplied from the bottom blowing tuyere (4) and the horizontal blowing tuyere (3), and an upper blowing lance is provided. Oxygen is blown in from (2).

The furnace body is provided with gas purge holes (5a) and (5b) in a furnace wall above a level at which a slag surface is formed during normal operation in the furnace, and gas is supplied from each gas supply system (6). It has become so. Each gas supply system (6) is provided with a pressure gauge (7) and a flow control valve (8).

In the present invention, for example, a steady constant flow rate (for example, 10 to 100 Nm ₃ / H) is supplied from the gas supply system (6) to the lower gas purge hole (5a).
(For example, N ₂ ) is supplied and blown into the furnace.

As the slag forms as a precursor to the slopping and the slag surface rises, the slag starts to clog the gas purge holes (5a), whereby the gas pressure on the supply side rises sharply. Such a change in gas pressure is measured by a pressure gauge (7).
Is measured. As for the gas pressure, a reference value (threshold value) serving as a reference for predicting the slotting is set in advance, and the pressure measured by the pressure gauge (7) as shown in FIG. At the time of X exceeding the value, occurrence of slotting is predicted.

When gas purge holes are provided in a plurality of upper and lower stages as shown in FIG. 1, gas is supplied to both gas purge holes (5a) and (5b), for example, as shown in FIG. ,
It is possible to foresee the occurrence of the slopping at the time Y at which both gas pressures exceed the reference value.

Actions to suppress the slopping performed based on the above prediction include: i) narrowing down the amount of acid supply ii) increasing the lance height iii) adding a slag forming calming agent IV) blowing pulverized coal into the bath. One or more anti-sloping actions are performed immediately after the anticipation of the occurrence of the anti-sloping.

〔The invention's effect〕

According to the present invention described above, it is possible to accurately predict the occurrence of the sloping with a sufficient time margin, and to take an appropriate preventive measure.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of the present invention. 2 (a) and 2 (b) show changes in the gas pressure on the supply side of the gas purge holes in the embodiment. In the figure, (1) is a smelting reduction furnace, (2) is a top blowing lance, (3) is a side blowing tuyere, (4) is a bottom blowing tuyere, and (5a)
(5b) is a gas purge hole, (6) is a gas supply system, and (7) is a pressure gauge.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Ichiro Kikuchi 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (72) Inventor Masahiro Muroya 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Japan Within Kokan Co., Ltd. (72) Inventor Kenji Takahashi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Kokan Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) C21B 11/00

Claims (2)

(57) [Claims] A gas is supplied at a constant flow rate into a furnace from a gas purge hole provided in a furnace wall above a slag surface level in a normal operation, and occurrence of slopping is predicted based on a pressure change on the supply side. A method for predicting slotting in smelting reduction, characterized in that: 2. A smelting reduction method according to claim 1, wherein a reference value of a pressure is provided, and occurrence of slotping is predicted when the pressure on the gas supply side exceeds the reference value. Slotting prediction method.