JP3364414B2 - Smelting reduction smelting of chrome ore - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a smelting reduction smelting method of chromium ore, and particularly to an attempt to effectively produce a chromium-containing molten metal which is a mother molten metal of stainless steel by directly using inexpensive chromium ore. Is.

[0002]

2. Description of the Related Art In recent years, in a smelting reduction furnace such as a converter, a so-called smelting reduction technology has been developed in which a chromium-containing molten metal is obtained by directly using an inexpensive chromium ore instead of using expensive alloy iron. That is, it is a process of reducing chromium ore containing a metal oxide such as iron oxide or chromium oxide in a molten slag by using a carbonaceous material such as coke.

Generally, coke is well known as a carbonaceous material used for the smelting reduction of chromium ore, but during the reduction period of chromium ore, the reaction between the metal oxide in the ore and the carbonaceous material is the reaction. Since the rate is controlled by the area of the interface, the reaction slows in coke, which is less likely to be thermally decomposed. As a result, not only the reduction of chromium ore but also the refractory life of the converter is adversely affected.

[0004] Therefore, the applicant used a method of using coal having a hard globe index (HGI) of 45 or less and a volatile component (VM) of 10% or less in order to improve the chromium reduction efficiency and the refractory melting loss. Regarding Japanese Patent Application No. 8-329431
No. specification.

[0005]

That is, the hard glove index (HGI) is 45 or less and the volatile component (VM) is 10
% Of coal reduces the size of the reaction interface between the metal oxide in the ore and the carbonaceous material and increases the area of the reaction interface between the metal oxide in the ore and the carbonaceous material after the addition in the furnace, which accelerates the reduction reaction of the chromium ore. It is. However, as compared with normal lump coke, the amount of C scattered in the dust during atomization is large and the scattering rate is also high, so that the in-furnace yield of carbonaceous matter becomes a problem. As shown in the above specification, the use of coal having a particle size of 3 mm or more in at least 90% or more can reduce the scattering rate of C into the dust. An increase in cost due to an increase in the number of processes for classifying the diameter by 3 mm poses a new problem.

The present invention solves the above problems in smelting reduction using coal having a hard globe index (HGI) of 45 or less and a volatile component amount (VM) of 10% or less as a carbonaceous material, and melting of chromium ore. The purpose is to propose a reduction smelting method.

[0007]

According to the present invention, carbonaceous material and chromium ore are added to molten iron contained in a metallurgical reaction vessel, oxygen gas is supplied to burn the carbonaceous material, and the heat of combustion produces chromium. When smelting ore is melted to produce a chromium-containing molten metal, coke is used as the carbonaceous material at the beginning or in the middle of the smelting reduction period, and then the hard globe index (HGI) is 45 or less and the amount of volatile components. (VM)
This is a smelting reduction smelting method for chromium ore, which is characterized by switching to coal of 10% or less.

Here, it is preferable to continue the smelting reduction with the coal having a hard globe index of 45 or less and a volatile component content of 10% or less for 15 minutes or more, in order to accelerate the reduction reaction of chromium ore, in particular.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The clarification process of the present invention will be described below. In the smelting reduction smelting performed by using scraps of anthracite and coke having the particle size distribution shown in Table 1, the carbon material brands used during the scrap melting period and the temperature rising period and the residual carbonaceous materials in the slag during the smelting reduction period The relationship with the grain size of was investigated. As shown in Fig. 1, when anthracite is used in the scrap melting period and the temperature rising period, the particle size distribution of the residual carbonaceous material C in the slag immediately after the start of blowing in the smelting reduction period is shown in Fig. 1 (D). As shown, the size of 20 mm or less, which is said to be effective in promoting the reduction of chromium, accounted for the majority.

On the other hand, when coke is used in the scrap melting period and the heating period, the particle size distribution of the residual carbonaceous material in the slag immediately after the start of blowing in the smelting reduction period is 20 as shown in FIG. 1 (A).
About 40% of the sizes are over mm. When coke is used during the scrap melting period and the temperature rising period, and when anthracite is used during the smelting reduction period of the next process, the particle size distribution of the residual carbonaceous material in the slag 10 minutes after the start of blowing during the smelting reduction period is ,
As shown in Fig. 1 (C), the size exceeding 20 mm is halved to about 20%. Furthermore, when coke is used during the scrap melting period and heating period, and when anthracite is used during the next smelting reduction period, the particle size distribution of the residual carbonaceous material in the slag 15 minutes after the start of blowing during the smelting reduction period is , As shown in FIG. 1 (D), 20
It is clear that the size of mm or more has almost disappeared, which is equivalent to the case when anthracite is used in the scrap melting period and the temperature rising period.

[0011]

[Table 1]

From the above experimental results, even when coke is used as the carbonaceous material during the scrap melting period and the heat-up period, it is necessary to operate using anthracite during the smelting reduction period of the next step, particularly this operation for 15 minutes. By continuing the above,
The residual carbonaceous material in the slag with a particle size exceeding 20 mm has almost disappeared,
It was found that a smelting effect equivalent to the operation using anthracite can be obtained throughout the entire process. In other words, even if the coke is used at the beginning or in the middle of the smelting reduction period, if the operation using anthracite is continued in the smelting reduction period, good smelting reduction smelting can be realized.

Therefore, in the present invention, as the carbonaceous material, coke is used at the beginning or in the middle of the smelting reduction period, and then the hard globe index (HGI) is 45 or less and the volatile component amount (VM) is 10% or less. By using coal,
As in the conventional method, the yield of carbonaceous material in the furnace was increased more than in the conventional method without impairing the reduction of the chromium ore, and the carbon scattering rate in the dust was suppressed.

[0014]

[Example] Smelting of chromium ore was carried out according to the smelting reduction blowing schedule shown in FIGS. 2 (A) and 2 (B). That is, in the comparative example shown in FIG. 2B, the carbon material with high thermal disintegration was used from the scrap melting period and the heating period to the smelting reduction period, whereas In the example shown in (2), the coke having a good yield in the furnace of C is used in the scrap melting period and the heating period, and the carbonaceous material having a high thermal disintegration property is used only in the smelting reduction period.

The smelting reduction smelting is carried out by using a 150t scale top-bottom blown smelting reduction furnace in which hot metal 130 which has been desiliconized and dephosphorized in advance is used.
After t was transported by a truck truck, 30 t of scrap was loaded into a smelting reduction furnace charged in advance. Here, as shown in FIG. 3, the used smelting reduction furnace 1 is provided with a top blowing lance 2 for supplying oxygen and a supply lance 3 for supplying chrome ore in the illustrated arrangement, and a carbonaceous material 4 is installed therein. It is used for melting and reduction smelting. The height of the upper blowing lance 2 was 4.2 m from the stationary molten steel surface, and the height of the supply lance 3 was 5.2 m from the stationary molten steel surface.

Next, top blown oxygen amount: 550 Nm ³ / min, bottom blown oxygen amount: 80 Nm ³ / min, bottom blown oxygen amount: 50 Nm ³ / mi
n is performed and the hot metal temperature is from 1550 ℃
The carbonaceous material was supplied at a constant ratio until the temperature reached 1600 ° C. Then, when the hot metal temperature reached a predetermined temperature, the supply of chrome ore was started and anthracite was used as the carbonaceous material. Supply amount: chromium ore: 1.35 kg / Nm ³ -O ₂ , carbonaceous material: 1.25 to 1.40 kg
The ratio was / Nm ³ -O ₂ . During this smelting reduction period, the temperature of the hot metal was measured periodically to keep the temperature in the range of 1550 to 1600 ° C. Then, after a lapse of a predetermined time (about 70 to 80 minutes), the charging lance was raised to stop the supply of chromium ore, and further the blowing for supplying only oxygen was carried out for about 5 to 7 minutes.

An embodiment according to the present invention will now be described with reference to FIG.
As shown in (A), coke was supplied at 1.45 kg / Nm ³ -O ₂ as carbon material during the scrap melting period and the heating period. On the other hand, in the comparative example according to the one shown in FIG. 2 (B), the anthracite (HGI = 3
(5, VM = 5.8%) was passed through an inclined vibrating screen called a jumping screen using a horizontally long mesh of about 4 mm × 17 mm and supplied at a ratio of 1.60 kg / Nm ³ -O ₂ .

In the above operation, the reduction rate of chromium ore and the C scattering rate in dust during the scrap melting period and the heating period were investigated. As shown in FIG. 4 and Table 2 as a result of the investigation, if the carbonaceous material used according to the present invention is selected,
While maintaining a high chromium reduction rate of 89% or higher, the carbon scattering rate in the dust during the scrap melting period and the heating period is about 20.
% Could be reduced.

[0019]

[Table 2]

[0020]

According to the present invention, in the smelting reduction refining method for chromium ores, coke is used as the carbonaceous material at the beginning or in the middle of the smelting reduction period, and then the hard lobe index (HGI) is 45 or less and volatilization occurs. By using coal having a component amount (VM) of 10% or less, it is possible to suppress carbon scattering into dust without inhibiting the smelting reduction of chromium ore.

[Brief description of drawings]

FIG. 1 is a diagram showing a particle size distribution of residual carbonaceous material in slag.

FIG. 2 is an explanatory diagram showing a smelting reduction blowing process of chromium ore.

FIG. 3 is a view showing a state in which carbonaceous material is being added into the converter.

FIG. 4 is a diagram showing chromium reduction rates in Examples and Comparative Examples.

[Explanation of symbols]

1 Smelting reduction furnace 2 Top blowing lance 3 supply lance 4 carbon materials

Front page continued (72) Inventor Hiroshi Nomura 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Chiba Works (56) References JP-A-9-227919 (JP, A) JP-A-10-25507 (JP, A) JP 10-219330 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C21C 5/28

Claims (2)

(57) [Claims] 1. A molten iron housed in a metallurgical reaction vessel, to which carbonaceous material and chromium ore are added, oxygen gas is supplied to burn the carbonaceous material, and the combustion heat heats and reduces the chromium ore to produce chromium. In melting the contained molten metal, as the carbonaceous material, coke is used at the beginning or in the middle of the smelting reduction period, and then the hard globe index (HGI) is 45 or less and the volatile component amount (VM) is 10% or less. A smelting reduction smelting method for chromium ore characterized by switching to coal. 2. The smelting reduction smelting method according to claim 1, wherein the smelting reduction is continued for 15 minutes or more with coal having a hard glove index of 45 or less and a volatile component content of 10% or less.