JPH0454722B2 - - Google Patents

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 and the smelting reduction of the chromium ore is also carried out. This invention relates to a thermoeconomic method for producing chromium-containing hot metal that can be carried out simultaneously. [Prior Art] Conventionally, as a method for producing chromium-containing hot metal for producing stainless steel, a method using an electric furnace has formed one technological system. In this method, a chromium source, coke, flakes, and optionally auxiliary materials are charged into a steelmaking arm furnace and melted to obtain chromium-containing hot metal. High carbon ferrochrome is usually used as the chromium source in this case. 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, the development of a method for directly melting and reducing chromium ore using a reducing agent such as carbonaceous material has been promoted. The trend is to focus on smelting and reducing chromium ore using a converter. For example, JP-A-58-77548, JP-A-59
-145758, JP 59-150059, JP 59-150060, JP 59-150061,
JP-A-59-150062 and others disclose melting and reduction of chromium ore using a converter. Also, JP-A-50-116317
The publication discloses a method of melting and reducing chromium ore using a special mixing tank. On the other hand, a patent application filed in 1983 by the same applicant as the present application
In No. 18219 (Japanese Unexamined Patent Publication No. 162718/1983),
We proposed a method of melting and reducing chromium ore as part of the chromium source by injecting powdered chromium ore into the tuyere of the vertical furnace using a special vertical furnace.
The gist of the method using a vertical furnace proposed by this 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 lower part of the furnace. The chromium source, iron source, carbon material, and slag material are charged from the upper raw material charging port.
By blowing hot air through the upper and lower tuyeres and at the same time supplying powdered chromium ore and heat generating material from the tuyeres into the furnace, chromium-containing hot metal is obtained while melting and reducing the powdered chromium ore. . In addition, a method for producing chromium-containing hot metal that is a partial improvement of the method proposed in JP-A-60-162718 has been published in Japanese Patent Application No. 1927-1985, Patent Application No. 9585-1982, and Patent Application No. 9585-1986. I proposed the issue. [Object of the Invention] The object of the present invention is to
This is a further improvement of the method for producing chromium-containing hot metal using a vertical furnace proposed in No. 18219 (Japanese Unexamined Patent Publication No. 60-162718), and more specifically, high-temperature oxygen-enriched air is supplied from the upper and lower tuyeres. By clarifying the setting standard for the relative distance (vertical distance) between the upper and lower tuyeres when powdered chromium ore is injected into the furnace from the upper tuyeres, powdered chromium ore can be injected into the furnace with a high chromium yield. It consists in melting and reducing under a certain temperature. [Summary of the Invention] 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 lower part of the furnace. A chromium source, iron source, carbon material, and slag material are charged through the charging port, and high-temperature oxygen-enriched air is blown through the upper and lower tuyeres. At the same time, powdered chromium ore and powdered slag material are charged from the upper tuyere. In the method of producing chromium-containing hot metal while melting and reducing powdered chromium ore by supplying powdered material consisting of ) is set below the tuyere limit interval (L ^* ). However, V _u and V _L are the flow rate (m ³ /min) of high-temperature oxygen-enriched air per tuyere blown from the upper and lower tuyeres, and D _ut and _Lt are the flow rates of the upper and lower tuyeres. The diameter (m) and D _PC are the average particle diameters (m) of the carbon material charged from the raw material charging port. 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 consists of a vertically long shaft as a whole, and the upper part of the furnace has a raw material charging port 1, and the lower part has upper tuyeres (multiple pieces).
A two-stage tuyere consisting of a lower tuyere 2 and a lower tuyere (plurality) 3 is 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 is supplied with this high-temperature oxygen-enriched air by the powdered chromium ore 15 in the container 6, the slag material 16 in the container 7, and the carrier gas 8, and this is blown into the furnace from the upper tuyere 2. . In the figure, 10 to 12
is a group of containers that contain high carbon ferrochrome as a chromium source, steel scrap as an iron source, coke as a carbon material, coal stone and fluorite as a slag material, and these raw materials charged at the top of the furnace are The raw material is charged into the furnace through the raw material charging port 1 while being weighed to a predetermined amount by a measuring device 13. Reference numeral 17 indicates a tap hole, and reference numeral 18 indicates the generated chromium-containing hot metal in the furnace. In addition,
When providing multiple upper and lower tuyeres, the upper tuyeres should be at the same height.
Multiple lower tuyeres will also be installed at the same height level. The present inventors have discovered that when blowing chromium ore using such a vertical furnace, in order to melt and reduce the powdered chromium ore that is blown into the furnace from the upper tuyeres at a high reduction rate, it is necessary to Tuyere spacing (vertical distance)
We conducted repeated experiments with a focus on how to set this. As a result, in order to achieve this objective, there is an upper limit on the spacing between the upper and lower tuyeres that must not be exceeded, and this upper limit is defined by V _u and _V Real high temperature oxygen enriched air flow rate ( ^m3 /
min)), D _ut and D _Lt (diameters of the upper and lower tuyeres (m)) and D _pc (average particle diameter (m) of the carbon material charged from the raw material charging port). I found out something. In other words, an example of the experimental results is shown in Figure 2, which shows the actual upper and lower tuyere spacing (L) set during the experiment and (L') calculated using the following equation (2). ) The chromium yield for each experiment is organized and expressed by the ratio L/L'. L′=(V _u /D _ut +V _L /D _Lt )/√ _PC (2) However, V _u , V _L , D _ut , D _Lt , and D _PC are as described above. As seen in the results in Figure 2, L/L' is 2.1
It can be seen that when the concentration exceeds ×10 ^-4 , the chromium yield deteriorates rapidly. In other words, in order to obtain a high chromium yield, it is necessary to set the upper and lower tuyere spacing below the tuyere limit spacing (L ^* ) expressed by equation (1). In this way, the spacing between the upper and lower tuyeres is determined by the critical tuyere spacing (L ^* ), which is determined by operational variables such as the flow rate of high-temperature oxygen-enriched air, the tuyere diameter, and the average grain size of the carbonaceous material.
It became clear that the following settings were required. This is considered to be based on the following reasons. Powdered chromium ore and powdered slag material injected from the upper tuyere are melted in the coke combustion area in front of the upper tuyere, and the melt is reduced while dripping through the coke packed bed. This reduction reaction is an endothermic reaction and proceeds more rapidly at higher temperatures. Therefore, in order to efficiently progress the melt reduction reaction of chromium ore, it is necessary to maintain the region where the melt drops, that is, the region between the upper and lower tuyeres, at a high temperature. A high-temperature coke combustion region exists in front of the upper and lower tuyeres, but the temperature decreases as the distance from this region increases, and this tendency becomes more pronounced as the coke combustion region becomes smaller. It can be understood that L′ in equation (2) above, which is determined by the flow rate of high-temperature oxygen-enriched air, the tuyere diameter, and the average particle size of the carbonaceous material, is a factor that determines the size of the combustion region of this coke. The combustion region expands as the value of L' increases. Therefore, if the ratio of the distance between the upper and lower tuyeres to the size of the coke combustion area, that is, L/L', becomes excessive beyond a certain threshold, the smelting and reduction reaction of chromium ore will not proceed quickly. .
That is, in this case, it is considered that a relatively low temperature region is formed between the upper and lower tuyeres, which reduces the reduction rate of the chromium ore and increases the amount of unreduced chromium in the slag. This will be demonstrated below with examples. Example 1 A vertical furnace with an inner diameter of 0.6 m as shown in Fig. 1 was used, and the interval between the upper and lower tuyeres was 0.4 m. Scraps, high carbon ferrochrome, and metallurgical coke with an average particle size of 0.015 m were charged, and the flow rate was 1.0 Nm ³ /min from the upper and lower tuyeres, each having an inner diameter of 16 mm.
High-temperature oxygen-enriched air having a temperature of 800° C. and an oxygen concentration of 28.5% was blown into the furnace, and a powder mixture shown in Table 2 was blown through the upper tuyere. Under this condition, the tuyere limit spacing (L ^* ) according to equation (1) is calculated to be 0.842 m. As a result, the unreduced chromium concentration in the slag taken out from the slag was 0.9%, and the chromium yield was 96.8%, making it possible to successfully melt and reduce chromium ore, as shown in Table 3. We were able to obtain chromium-containing hot metal with the following composition.

【table】

【table】

[Table] Example 2 Chromium-containing hot metal was produced under the same conditions as Example 1 (L ^* = 0.842 m) except that the interval between the upper and lower tuyeres was 0.75 m. As a result, the unreduced chromium concentration in the slag was 1.0%, and the chromium yield was 96.5%, and the chromium ore could be melted and reduced as well as in Example 1. The composition of the obtained chromium-containing hot metal is shown in Table 4.

[Table] Example 3 (Comparative Example) Chromium-containing hot metal was produced under the same conditions as Example 1 (L ^* = 0.842 m) except that the interval between the upper and lower tuyeres was 0.96 m. As a result, the unreduced chromium concentration in the slag was as high as 3.4%, and the chromium yield was
It was a low value of 88.1%. The composition of the obtained chromium-containing hot metal is shown in Table 5.

【table】 [Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a vertical furnace suitable for carrying out the method of the present invention, and FIG. 2 is a diagram showing the relationship between chromium yield and L/L' as explained in the text. 1... Raw material charging port in the upper part of the furnace, 2... Upper tuyere,
3...Lower tuyere, 4...Hot stove, 5...Oxygen source,
15... Powdered chromium ore, 16... Powdered slag material.

Claims (1)

[Scope of Claims] 1. When producing chromium-containing hot metal using a tight 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 raw material charging port in the upper part Charge chromium source, iron source, carbon material and slag material from
By blowing high-temperature oxygen-enriched air through the upper and lower tuyeres and at the same time supplying powdered material consisting of powdered chromium ore and powdered slag material into the furnace from the upper tuyere, the powdered chromium ore is In the method of producing chromium-containing hot metal while melting and reducing, it is recommended that the vertical distance between the upper and lower tuyeres be set to the tuyere limit distance (L ^{* or} less) expressed by the following formula (1). Characteristic method for producing chromium-containing hot metal, However, V _u and V _L are the flow rates (m ³ /min) of high-temperature oxygen-enriched air per tuyere blown from the upper and lower tuyeres, and D _ut and D _Lt are the flow rates of high-temperature oxygen-enriched air per tuyere (m 3 /min), The diameter (m) of D _pc is the average particle diameter (m) of the carbon material charged from the raw material charging port.