JPH0559416A - Method for operating two step tuyere type smelting reduction furnace - Google Patents

Abstract

PURPOSE:To provide an operational method, in which the yield of molten iron can be drastically improved, by lowering impurity concn. of Si, etc., in the molten iron and at the same time, FeO concn. in slag in the operation in a two step tuyere type smelting reduction furnace. CONSTITUTION:At the time of blowing oxygen-containing high temp. gas together with ore and flux from the upper tuyeres and blowing the above oxygen-containing high temp. gas from the lower step tuyeres, the ratio of blowing quantity of the oxygen-containing high temp. gas blown from the upper step tuyere and blowing quantity of the oxygen-containing high temp. gas blown from the lower step tuyere is controlled in the range of 5-6 to operate the furnace.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a vertical smelting reduction furnace having two upper and lower tuyeres (hereinafter referred to as "two-stage tuyere-type smelting reduction furnace"). More specifically, the ratio of (air volume of oxygen-containing high-temperature gas blown from the upper tuyeres) / (air volume of oxygen-containing high-temperature gas blown from the lower tuyeres), (hereinafter, referred to as the ratio between the upper tuyere air volume and the lower tuyere air volume) Abbreviated.) For controlling the Si concentration in the hot metal and improving the yield of the hot metal.

[0002]

2. Description of the Related Art Conventionally, as the ventilation control of a two-stage tuyere type smelting reduction furnace, the techniques of Japanese Patent Laid-Open Nos. 63-153208 and 62-227015 are known. The former prevents fluctuations in the hot metal temperature and components that occur as a result of instability between the packed bed height and the temperature in the furnace due to changes in the brand of the charged coal and fluctuations in the particle size distribution of the charged material, and ensures stable operation. The latter is intended to reduce the amount of air blown, the amount of oxygen enriched and the amount of carbonaceous material used when producing the same amount of hot metal. In addition,
Each of the techniques disclosed in the above publications relates to a method of operating a two-stage tuyere type smelting reduction furnace that forms a packed bed of a carbonaceous solid reducing agent.

On the other hand, the hot metal is subjected to a removal process of impurities such as descaling, dephosphorization and desulfurization in the next step. Therefore, the production of hot metal with a low content of impurities has been strongly desired. However, in order to reduce the impurities and reduce the FeO concentration in the slag to improve the hot metal yield, the ratio of the upper tuyere air volume to the lower tuyere air volume is controlled within a predetermined range. The technology didn't work.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems and has a low impurity content,
Further, a method for operating a two-stage tuyere type smelting reduction furnace is provided in which the oxide is sufficiently reduced and the FeO concentration in the slag is reduced to 1% by weight (hereinafter abbreviated as "%") or less to improve the hot metal yield. The purpose is to do.

[0005]

The present invention is a two-stage tuyere type smelting reduction furnace in which oxygen-containing high temperature gas is blown together with ore and flux from the upper stage tuyere and the oxygen-containing high temperature gas is fed from the lower stage tuyere. A method for operating a two-stage tuyere smelting reduction furnace, characterized in that the ratio of the upper-stage tuyere air flow rate to the lower-stage tuyere air flow rate is controlled to be 1.5 or more and 6 or less when blowing.

[0006]

In order to obtain a clue of the technique for reducing the Si concentration in the hot metal, the inventors of the present invention have conducted a detailed investigation of the operation result data, and found that the same raw material composition is present in the hot metal. It has been found that the Si concentration of the above may differ.

[0007] Further investigation on this point,
It was found that when the Si concentration in the hot metal was different, the ratio of the upper stage tuyere air volume and the lower stage tuyere air volume was different. Therefore, in order to confirm this by making a hypothesis that "Si concentration in the hot metal is related to the ratio of the upper stage tuyere air flow rate to the lower stage tuyere air flow rate," the following two-stage tuyere smelting reduction furnace The experiment was conducted by changing the ratio of the upper stage tuyere air volume to the lower stage tuyere air volume in the range of 0.7 to 7.

Note (1) Two-stage tuyere smelting reduction furnace a. Inner diameter (m) 1.5 b. Furnace height (m) 4 c. Number of tuyeres (tiers) 2 (a) Upper tier tuyeres (books) 3 (b) Lower tier tuyeres (books) 3 (c) Upper tier tuyeres spacing (mm) 1500 (2) Operating conditions a ． Air volume (oxygen concentration 40% by volume) (Nm ³ / h) 990 b. Oxygen-containing high temperature gas temperature (° C) 1000 c. Carbonaceous material (coke) supply amount (Kg / h) 905 d. Blow-in amount from upper tuyeres (Kg / h) (a) Iron ore powder (particle size 2 mm or less) 580 (b) Limestone powder (particle size 1 mm or less) 100 (c) Silica powder (particle size 1 mm or less) 48

The results are shown in FIG. 1. When the ratio of the upper tuyere air volume to the lower tuyere air volume is 1.5 to 7, the Si concentration in the hot metal is almost constant and 1.0% or less. However, it was found that the Si concentration in the hot metal drastically rises when the ratio of the upper and lower tuyere air volumes is 1.5 or less. Therefore, in order to reduce the Si concentration in the hot metal, it was found that an operating method in which the ratio of the upper-stage tuyere air flow rate to the lower-stage tuyere air flow rate is controlled to be 1.5 or more and 6 or less is effective. The reason for this is considered as follows (see FIG. 3). That is, when the total amount of the upper-stage tuyere 1 air amount and the lower-stage tuyere 2 air amount is the same and the ratio is 1.5 or more, the amount of heat generated in front of the lower-stage tuyere relatively decreases. Therefore, the ash 7 in the carbonaceous material 8 supplied from above is SiO 2.
_{The amount of 2} reduced in front of the lower tuyere decreases, and SiO (g)
The amount of S generated decreases, and S that dissolves in the dripping molten ore 9
Since the amount of i is small, the Si concentration in the hot metal decreases.

On the other hand, as shown in FIG. 2, when the ratio of the upper stage tuyere air amount to the lower stage tuyere air amount exceeds 6, the FeO concentration in the slag becomes high. This is because the amount of heat generated in front of the lower tuyeres is reduced, and the iron ore blown from the upper tuyeres is not completely reduced. The temperature range of the oxygen-containing high temperature gas according to the present invention is usually 900 ° C. to 1200 ° C., and the oxygen concentration of the oxygen-containing high temperature gas in this temperature range is 30 to 30 ° C.
45% by volume is preferred. Here, the case of hot metal production was described as an example, but the operating method of the present invention is C
The same can be applied to alloy pigs containing r, Mn, Ni and the like.

Further, the present invention can be applied not only to a packed bed type for forming a carbonaceous material packed bed, but also to a non-packed bed type two-stage tuyere type smelting reduction furnace for forming a fluidized bed or the like. Further, according to the present invention, the FeO concentration in the slag is reduced, so that damage to the refractory is reduced. Furthermore, according to the present invention, the S concentration in the hot metal can be stabilized at a low level of 0.05% or less.

[0012]

[Example] In the above-mentioned two-stage tuyere type smelting reduction furnace, operating conditions,
The operation results when changing only the ratio of the upper and lower tuyeres

The results are shown in [Table 1]. That is, in Comparative Example No. 1 in which the ratio of the upper stage tuyere air volume to the lower stage tuyere air volume was 1. In 1 S in hot metal
No. of Comparative Example in which the i concentration was high and the ratio of the upper and lower tuyere air volumes was 7. Although the FeO concentration is high in Example 7, No. 7 in the example of the method of the present invention. 2 to No. In No. 6, both the Si concentration in the hot metal and the FeO concentration in the slag were low. As is clear from the above, according to the operation method of performing ventilation control according to the present invention, it is possible to manufacture hot metal having a low Si concentration at a high yield.

[0013]

[Table 1]

[0014]

As described above, according to the operating method of the present invention, the Si concentration in the hot metal, which was around 2% in the past, is reduced to 1% or less, and the FeO concentration in the slag is around 3.0% in the conventional case. To 1% or less, and the hot metal yield can be significantly improved.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing a relationship between a ratio of an upper stage tuyere air amount and a lower stage tuyere air amount and a Si concentration in hot metal.

FIG. 2 is a characteristic diagram showing the relationship between the ratio of the upper stage tuyere air volume to the lower stage tuyere air volume and the FeO concentration in the slag.

FIG. 3 is a schematic explanatory view of the vicinity of the tuyere of a two-stage tuyere type smelting reduction furnace.

[Explanation of symbols]

 1 Upper stage tuyeres 2 Lower stage tuyeres 3 Upper stage laceways 4 Lower stage laceways 5 Ore 6 Flux 7 SiO-reducing gas 8 Carbonaceous material 9 Molten ore to be dropped 10 Oxygen-containing high temperature gas 11 Two-stage tuyere type melt reduction furnace wall

Claims (1)

[Claims] 1. In a two-stage tuyere type smelting reduction furnace, an oxygen-containing high-temperature gas is blown together with ore and flux from an upper-stage tuyere and is blown from an upper-stage tuyere when the oxygen-containing high-temperature gas is blown from a lower-stage tuyere. A method for operating a two-stage tuyere type smelting reduction furnace, characterized in that the ratio of the air flow rate of the oxygen-containing high temperature gas to the air flow rate of the oxygen-containing high temperature gas blown from the lower tuyeres is controlled to be 1.5 or more and 6 or less.