JPS6254007A - Production of molten chromium iron - Google Patents

Abstract

PURPOSE:To execute melt reduction with good thermal efficiency in a melt reduction method of chromium ore using a vertical furnace by controlling the rate of blowing the high-temp. air enriched with oxygen to be blown from two stages of upper and lower tuyeres to a specific value or above. CONSTITUTION:Iron sources, carbonaceous materials and slag forming materials and, it necessary, chromium sources are charged through a raw material charging port 1 into the vertical furnace in the stage of producing the molten chromium iron by using the vertical furnace having the port 1 in the upper part of the furnace and two stages of the upper and lower tuyeres 2, 3 near the lower part. The high-temp. air enriched with oxygen is blown through the upper and lower tuyeres 2, 4, at the same time, the powdery chromium ore and powdery slag forming materials are supplied into the furnace through the upper tuyere 2. The molten chromium iron is produced while the powdery chromium ore is subjected to melt reduction. The rate of blowing the high-temp. air enriched with oxygen to be blown through the tuyeres 2, 3 is controlled to >=100m/sec.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method for producing chromium-containing hot metal without using electricity as energy for smelting, in which chromium ore is used as part of the chromium source. The present invention relates to a thermoeconomic method for producing chromium-containing hot metal in which smelting and reduction of chromium ore can be carried out at the same time.

[Conventional technology]

From before, stainless steel mi1! One of the technological systems for producing chromium-containing hot metal for steel production is the method using an electric furnace. In this method, a chromium source, coke, flux, and optionally auxiliary materials are charged into a steelmaking arc furnace and melted to obtain chromium-containing hot metal. High carbon ferrochrome is usually used as the chromium source. An electric furnace is also used to produce this high carbon ferrochrome, and in this case semi-reduced pellets of chromium ore or sintered ore are used. Since this conventional method consumes a very large amount of electricity, in recent years there has been a push to develop a method for directly melting and reducing chromium ore using a reducing agent such as carbonaceous material. The trend seems to be to focus on smelting and reducing chromium ore using converters. For example, JP-A-58-77
Publication No. 548.

JP-A-59-145758, JP-A-59-150
059, JP 59-150060, JP 59-150061, JP 59-150 (1)
Publication No. 62 and the like disclose melting and reduction of chromium ore using a converter. Further, Japanese Patent Application Laid-Open No. 116317/1983 discloses a method for melting and reducing chromium ore using a special mixing tank.

On the other hand, Japanese Patent Application No. 18219/1989 filed by the same applicant as the present application
In this issue, we proposed a method for melting and reducing powdered chromium ore as part of the chromium source by using a special vertical furnace and injecting powdered chromium ore as part of the chromium source into the tuyeres of this vertical furnace. The gist of the method using a vertical furnace proposed by the applicant is to produce chromium-containing hot metal using a vertical furnace that has a raw material charging port in the upper part of the furnace and two upper and lower tuyeres near the bottom of the furnace. The chromium source, iron source, carbon material, and slag material are charged from the upper raw material charging port, and hot air is blown from the upper and lower tuyeres, and at the same time, powdered chromium ore is heated from each tuyere. By supplying the powdered chromium ore and powdered slag forming material into the furnace, chromium-containing hot metal is obtained while the powdered chromium ore is melted and reduced.

[Purpose of the invention]

The present invention is an attempt to further improve the method for melting and reducing chromium ore using a vertical furnace, which was proposed in the above-mentioned Japanese Patent Application No. 18219/1982. In particular, we aim to solve unresolved problems regarding the reaction behavior near the two-stage tuyere of this vertical furnace and provide a method for melting and reducing chromium ore with good thermal efficiency. .

[Means to achieve the purpose]

The present invention provides a method for producing chromium-containing hot metal using a vertical furnace having a raw material charging port in the upper part of the furnace and upper and lower tuyeres near the bottom of the furnace. At the same time, high-temperature oxygen-enriched air is blown into the upper and lower tuyeres, and at the same time, powdered chromium ore, 1 heating material, and powdered slag-making material are charged from the upper tuyeres. In the method of producing chromium-containing hot metal while melting and reducing the powdered chromium ore by supplying it into the furnace, the blowing speed of the high-temperature oxygen-enriched air blown from the upper and lower two stages of tuyeres is set to Loom/
It is characterized by controlling more than s.

FIG. 1 shows an example of a vertical furnace for carrying out the method of the present invention. As shown in the figure, this vertical furnace has a vertically elongated shaft as a whole, and the upper part of the furnace has a raw material charging port 1, and the lower part has two parts, each consisting of an upper tuyere 2 and a lower tuyere 3. Tiered tuyeres are provided. 4 is a hot air stove, and hot air obtained from this hot air stove 4 is supplied to each tuyere 2 and 3. At this time, the hot air can be enriched with oxygen by the oxygen source 5. The upper tuyere 2 receives this high-temperature oxygen-enriched air as well as powdered chromium ore 15 in the container 6 and powdered heat generating material 16 in the container 7. Further, although not shown, powdered slag material is supplied by a carrier gas 8 and blown into the furnace. As the powder heat generating material 16, ferroalloy powder such as high carbon ferrochrome powder or ferrosilicon powder, SiC or C
A substance that generates heat by reacting with oxygen, such as aC, is used.

In the figure, numerals 10 to 12 are containers containing high-carbon ferrochrome as a chromium source, steel scrap as an iron source, coke as a carbon material, and limestone and fluorite as a slag material. The raw material charged at the top of the furnace is weighed to a predetermined amount by a measuring device 13 and charged into the furnace from the raw rice bag entrance 1. 17 is the taphole.

Day 1 shows the chromium-containing hot metal produced in the furnace.

The present inventors investigated how to melt and reduce powdered chromium ore, which is injected into the furnace from the upper tuyere, in a thermally efficient manner when injecting chromium ore using such a vertical furnace. We conducted repeated experiments with this point in mind. In other words, the powdered chromium ore, which is injected into the furnace from the upper tuyere together with the powdered heat generating material and powdered slag material, melts in the coke combustion area in front of the upper tuyere, and the melt drips down the coke packed bed. This reduction reaction is endothermic. Therefore, if heat is not efficiently supplied from the coke combustion gas generated in front of the lower tuyere, which is the heat medium, to the area where the molten chromium ore is being reduced, the smelting reduction reaction of the chromium ore will be significantly affected. As a result, the yield of chromium decreases and it becomes difficult to produce stable chromium-containing hot metal. As a result of the inventors' experimental study of power transformation, this phenomenon is caused by conditions in which the molten chromium ore in front of the upper tuyere selectively drips in a narrow area with respect to the cross section of the furnace. It was found that this occurs when

The gist of the present invention is to distribute the dripping area of the molten chromium ore, which has been blown into the furnace from the upper tuyere into a molten state, over a wide area with respect to the cross section of the furnace, in order to prevent such conditions from occurring. be. The most effective and simple means to achieve this is to increase the velocity (Vb) of high-temperature oxygen-enriched air blown from the upper and lower tuyeres, as a result of numerous experiments conducted by the present inventors.

(Vb)≧1100(/s).

Figure 2 shows that during an experiment to produce chromium-containing hot metal using an experimental furnace, the furnace was rapidly cooled so that the conditions inside the furnace could be preserved, and then the furnace was dismantled and investigated. This diagram illustrates the situation inside the furnace near the tuyere. As shown in FIG. 2, during the production of chromium-containing hot metal, a space called a raceway 20 in which carbonaceous materials such as metallurgical coke soot is burned is formed at the front of the upper tuyere 2 and the lower tuyere 3 inside the furnace. Surrounding this raceway 20, there is a region 21 in which molten chromium ore is blown into the upper tuyere 2 together with a powdered heat generating material and a slag-forming material and drips into a packed bed of carbon material. In this region 21, chromium oxides and iron oxides present in molten oxides such as chromium ore are reduced by carbon in the carbonaceous material, producing molten metal with a high chromium concentration, and Chromium concentration decreases. As a result, chromium-poor molten oxide and chromium-rich molten metal drip onto the bottom of the furnace.
In addition, molten material such as steel scraps charged from the upper part of the furnace drips down and chromium-containing hot metal eventually accumulates at the bottom of the furnace. In FIG. 2, 22 indicates the area where molten oxide is accumulated.
3 indicates a region where chromium-containing hot metal accumulates, and 24 indicates a region where steel scraps charged from the upper part of the furnace melt and drip.

Under such conditions inside the furnace during the production of chromium-containing hot metal, the velocity of high-temperature oxygen-enriched air (V
It was found that when b) was set to '(Vb) < 1100 (/s), the chromium ore melt was selectively dripping in a narrow area with respect to the cross section of the furnace. . For this purpose, from the combustion gas of the carbonaceous material generated in front of the lower tuyere 3 to this dripping area 21.

The reaction heat necessary for melting and reducing the chromium ore was not efficiently supplied, and as a result, the melting and reducing of the chromium ore in the furnace did not progress smoothly, resulting in a poor chromium yield. On the other hand, if the velocity (Vb) of high-temperature oxygen-enriched air is set to (Vb)≧1100 (/s) with other operating conditions being the same, the area where the melted chromium ore drips were widely distributed across the cross section of the furnace. For this purpose, heat is efficiently supplied from the combustion gas of the carbonaceous material to this dripping region 21, and as shown in FIG. 3, out of the amount of heat supplied into the furnace,
Proportion of heat effectively utilized for smelting reduction of chromium ore,
In other words, the thermal efficiency is (Vb) < 1100 (/s)
It was found that the yield of chromium was higher than that when the experiment was conducted under the conditions of .

In addition, the velocity (Vb) of high-temperature oxygen-enriched air blown into the furnace
can be calculated using a linear equation.

Vb = BV/ (rt・(DT/2)21
Flow rate of oxygen-enriched air (m'/s); Tuyere diameter (m)
.

π: Pi.

The results of the experiment using the experimental reactor are described below.

Example 1 Top charging materials were charged from the top of a vertical furnace with a furnace inner diameter of 0.6 m as shown in Fig. 1 in the amounts shown in Table 1.
From the upper and lower tuyeres, each with an inner diameter of 16 mm.

High-temperature oxygen-enriched air with a temperature of 800°C and an oxygen concentration of 28.5% was blown into the furnace at a speed of 284 mha at a flow rate of 1 Nm'/min, and from the upper tuyere, A mixture of powders shown in was blown into the furnace. As a result, the unreduced chromium concentration in the slag taken out from the slag was 0.8%, and the chromium yield was 97.9%, making it possible to melt and reduce chromium ore well. Chromium-containing hot metal with the composition shown in the table could be obtained.

Table 1 (Materials charged at the top of the furnace) Table 2 (Materials blown into the upper tuyeres) Table 3 (Composition of chromium-containing hot metal, weight %) Example 2 (comparative example) High-temperature oxygen enrichment from the upper and lower tuyeres with an inner diameter of 35 mm Chromium-containing hot metal was produced under substantially the same conditions as in Example 1, except that the rate of oxidizing air was blown at 68 m/s.

In this case, the unreduced chromium concentration in the slag was 3.3%, and the chromium yield was 91.6%. The composition of the obtained chromium-containing hot metal was as shown in Table 4.

Table 4 (Composition of chromium-containing hot metal weight %)

[Brief explanation of drawings]

Part 1 is a schematic cross-sectional view of a vertical furnace suitable for implementing the method of the present invention, Figure 2 is a schematic cross-sectional view showing the inside of the furnace near the upper and lower tuyeres, and Figure 3 is a schematic cross-sectional view of the furnace with high-temperature oxygen-enriched air. This is a diagram showing the relationship between the blowing speed and energy efficiency. The energy efficiency in the figure indicates the ratio of the amount of heat effectively used for melting and reducing the chromium ore to the heat input. 1.Charging raw materials in the upper part of the furnace 0.2..Upper tuyere. 3. Lower tuyere, 4. Hot blast furnace, 5. Oxygen source. 15... Powdered chromium ore, 20... Raceway. 21... Dripping area of molten chromium ore, 22... Area where molten oxides accumulate, 23... Area where chromium-containing hot metal accumulates, 24... Steel scrap charged from the upper part of the furnace melts and drips. area.

Claims (1)

[Claims] When producing chromium-containing hot metal using a vertical furnace with a raw material charging port in the upper part of the furnace and two upper and lower tuyeres near the bottom of the furnace, a chromium source, an iron source, Charcoal material and slag material are charged, and high-temperature oxygen-enriched air is blown from the upper and lower tuyeres, and at the same time, powdered chromium ore is poured from the upper tuyeres.
By supplying heat generating material and powdered slag material into the furnace,
This method for producing chromium-containing hot metal while melting and reducing powdered chromium ore is characterized by controlling the blowing speed of the high temperature oxygen-enriched air blown from the upper and lower two stages of tuyeres to 100 m/s or more. A method for producing chromium-containing hot metal.