JPH10317032A - Smelting and reduction method of chromium ore - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a smelting reduction method of chromium ores to improve the yield of the chromium reduction and the yield of the carboneous material using a converter type smelting reduction furnace with the top-blown function. SOLUTION: In smelting the molten metal containing chromium by adding chromium ores in a converter type smelting reduction furnace with the top-blown function together with the carbon-containing substance, and feeding oxygen through top-blow, the bulk specific gravity of the in-furnace slag is regulated to be smaller than the true specific gravity of the carbon-containing substance to be added. The carbon-containing substance to be added is preferably >=3 mm in grain size and/or heat-collapsible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for smelting and reducing chromium ore by adding a carbon-containing substance to chromium ore and smelting and reducing chromium ore.

[0002]

2. Description of the Related Art Conventionally, smelting of stainless steel has been performed using ferrochrome produced by reducing chromium ore or the like in an electric furnace with carbon. However, since expensive electric power is used, the cost of ferrochrome is high. As a result, the production cost of stainless steel is high. In order to solve this problem, there has been known a method of melting a chromium-containing molten metal by reducing carbon in a pre-reduced semi-reduced chromium pellet using a top-bottom blowing converter without using electric power. ing. In addition, a method has been proposed in which the chromium ore is directly reduced to obtain a chromium-containing molten metal. (JP
JP-A-58-9959 and JP-A-55-91913) Also, JP-A-7-41872 discloses the use of a heat-degradable carbon material to prevent metal particles from adhering to the carbon material. Thus, a method for reducing the metal loss and increasing the reduction reaction rate has been disclosed.

[0003] Japanese Patent Application Laid-Open No. 1-195212 discloses a method for maintaining the bulk specific gravity of slag at 0.5 to 1.5 when a carbon material of 1 mm or less is blown into slag in an iron bath type smelting reduction furnace. Have been.

[0004]

The smelting reduction method of semi-reduced chromium pellets requires equipment for producing chromium pellets, and has a problem that the cost is higher than the method of smelting reduction of chromium ore directly. . On the other hand, in the smelting reduction method of chromium ore, the oxide (Cr ₂ O ₃ , Fe
Since the charging rate of O) increases, there is a problem that the reduction reaction rate must be increased in order to make the amount of chromium reduction per unit time the same as in the conventional method. For this purpose, it is effective to increase the surface area of the carbon-containing substance, which is the main reduction reaction interface, but when the same carbon-containing substance as in the past is used, it is necessary to increase the amount of the carbon-containing substance added. . This increase in the amount of the carbon-containing material added causes not only the increase in the amount of addition itself to increase the cost, but also the carbon-containing material remaining in the treated slag.
It is also harmful because it has an adverse effect on slag reuse, and greatly reduces the benefits of the smelting reduction method of chromium ore.

[0005] The present invention advantageously solves the above-mentioned problems,
An object of the present invention is to propose a smelting reduction method of chromium ore that can obtain a high carbon material yield. Although the above object can be solved by using a carbonaceous material having a fine particle size, the use of such a fine carbonaceous material has a problem that the addition yield is low and the amount of dust generated increases. On the other hand, in Japanese Patent Application Laid-Open No. 7-41872, in the state where the carbon material surface temperature is 800 ° C. or less, the charging method is adjusted so as to reach the slag or the metal, so that the slag before the thermal collapse of the carbon material is heated. Alternatively, a method of being involved in metal is disclosed.

However, when the present inventors conducted experiments by changing the carbon material input height, the yield of the carbon material did not change even under the condition that the surface temperature could be kept at 800 ° C. or less, and the exhaust gas flow rate was not changed. There was a tendency for the carbonaceous material yield to decrease with the increase. In the vicinity of the furnace port during the experiment, blowing of carbonaceous material powder was observed along with the pulsation of the furnace pressure, and a large amount of carbonaceous material was observed above the slag based on observations inside the furnace and sampling results of the slag after the experiment. Was observed.

[0007] From these results, although a part of the carbon material charged into the furnace is caught in the slag and metal,
Most of them were presumed to be floating on the slag or suspended in the furnace space. For this reason, it is considered that the scattering of the carbonaceous material does not decrease even when a treatment for preventing the thermal collapse during the charging is performed. As described above, the method of adding the thermally collapsed carbon material has a problem that the addition yield is low.

On the other hand, in the method disclosed in Japanese Patent Application Laid-Open No. 1-195212, pulverized coal having a particle size of 1 mm or less is directly blown into foamed slag because it is used for smelting in a smelting reduction furnace. It is a way to put it. In order to blow pulverized coal directly into the slag, it is necessary to provide a nozzle on the side of the furnace body as specified in the publication. However, installing a nozzle on the side of the furnace body increases the load on the refractory lining of the furnace and significantly reduces the life of the furnace. Further, during the smelting, the molten iron and the molten slag in the furnace vibrate violently, so that the outlet pressure of the nozzle installed on the side of the furnace pulsates greatly, and stable blowing cannot be continued. Further, when the molten iron and the molten slag in the furnace swing extremely, there is a problem that the tip of the nozzle is exposed from the slag and the pulverized coal blown into the furnace space.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to improve the chromium reduction yield and the carbon material yield in the smelting reduction process using a converter. It has been found that the carbon material yield is greatly improved by controlling the apparent specific gravity of the slag to a certain value or less, greatly affected by the apparent specific gravity of the slag.

First, an experiment on which the present invention is based will be described. The present inventors, in a 5 ton test converter, add chromium ore to the converter and a thermo-disintegrable carbon-containing substance that is refined when charged into the furnace, and supply oxygen by top and bottom blow to supply chromium ore. Melt reduction treatment was performed. In addition, the added carbon-containing substance was made into three kinds from which specific gravity differs, and the influence of the specific gravity of the carbon-containing substance was examined.

First, dust scattered from the converter during this process was analyzed, and one example is shown in Table 1.

[0012]

[Table 1]

Dust is mainly composed of carbon (TC) originating from a carbon-containing substance, iron (T.Fe, M.Fe) originating from metal, chromium (T.Cr) originating from ore, and CaO originating from slag.
, SiO ₂ ratio is extremely small. This indicates that slag is hardly scattered. Further, it can be estimated that the carbon-containing substance does not scatter once in the slag, or that the carbon-containing substance scatters after being separated from the slag.

Further, when the scattering rate of the added carbon-containing substance was examined, it was found that the scattering rate of the added carbon-containing substance had a strong correlation with the apparent specific gravity of the slag, as shown in FIG. That is, the scattering rate increases as the apparent specific gravity of the slag increases at the point where the apparent specific gravity of the slag is equal to the true specific gravity of the carbonaceous material. In addition, it was found that when the particle size at the time of injection was larger than the critical particle size that escaped due to the flow rate of the exhaust gas from the furnace port, the particle size distribution of the carbon-containing material did not significantly affect the scattering rate of the carbon-containing material. Furthermore, it was found that the wettability of the slag did not significantly affect the scattering rate of the carbon-containing substance.

The present invention has been made based on the above findings. That is, the present invention relates to a smelting reduction of chromium ore in which a chromium ore is melted by adding chromium ore together with a carbon-containing substance to a converter type smelting reduction furnace having an upper and lower blowing function and supplying oxygen by upper and lower blowing. In the method, the slag present in the converter type smelting reduction furnace is smelted and reduced by adjusting the apparent specific gravity of the slag to be smaller than the true specific gravity of the carbon-containing material.

In the present invention, it is preferable to use a carbon-containing substance having a particle diameter of 3 mm or more.
It is preferable to use a thermally decayable carbon-containing substance.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a converter type smelting reduction furnace having a top-bottom blowing function is used. The chromium ore is added to the converter together with the carbon-containing material, and the carbon-containing material is burned by supplying oxygen by top and bottom blowing, and the heat of combustion melts and reduces the chromium ore to melt the chromium-containing molten metal. Here, the carbon-containing substance is added from the furnace.

The use of the top and bottom blown converter enables a high productivity smelting reduction by supplying a large amount of oxygen gas from both the top and bottom,
It is also effective from the viewpoint of increasing the reduction reaction rate of the metal oxide in the slag by vigorous stirring by the bottom blow gas. In the present invention, the carbon-containing substance is added from the furnace.
This eliminates the need for special blowing equipment such as providing nozzles on the furnace side wall, and reduces the load on the refractory inside the furnace,
In addition, the carbon-containing substance can be stably blown without problems such as unstable blowing and blow-through.

In the present invention, the smelting reduction treatment is performed by adjusting the apparent specific gravity of the slag present in the converter type smelting reduction furnace to be smaller than the true specific gravity of the carbon-containing substance to be added. The adjustment of the apparent specific gravity of the slag is preferably performed by adjusting the lance height to adjust the slag forming, adjusting the amount of residual carbon material, adjusting the slag component, and the like. When the apparent specific gravity of the slag is larger than the true specific gravity of the carbon-containing substance to be added, there is a disadvantage that the carbon-containing substance is hardly caught in the slag, and the scattering rate of the carbon-containing substance increases. For this reason, the apparent specific gravity of the slag is adjusted to be smaller than the true specific gravity of the carbon-containing substance to be added.

In the present invention, it is preferable to use a carbon-containing substance having a particle diameter of 3 mm or more. When the particle diameter of the carbon-containing substance to be blown is less than 3 mm, if the terminal velocity of the added carbon-containing substance is lower than the flow rate of the exhaust gas at the furnace port, the added carbon-containing substance dissipates outside the furnace together with the exhaust gas. If the particle size of the carbon-containing substance to be blown is 3 mm or more, under normal operating conditions, the final velocity of the added carbon-containing substance becomes larger than the flow rate of the exhaust gas at the furnace port,
Dissipation of the carbon-containing material outside the furnace can be prevented.

On the other hand, when a carbon-containing substance having a large particle size is used, the area of the reaction interface with the slag becomes small, and there is a concern that the reduction of chromium ore may be insufficient.
It is preferable to use a thermally decayable carbon-containing substance. By using a carbon-containing substance having thermal disintegration properties, the carbon-containing substance that has entered the slag is thermally disintegrated in the slag and decomposed into particles having a small particle size. As a result, the area of the reaction interface between the slag and the carbon-containing substance increases, and poor reduction of chromium ore can be prevented. In the present invention, the apparent specific gravity of the slag is adjusted to be smaller than the true specific gravity of the carbon-containing substance to be added, whereby the carbon-containing substance that has been thermally collapsed into small particles also remains in the slag without being scattered. Will be able to do it.

[0022]

EXAMPLE A chromium ore was smelted and reduced using a converter type smelting reduction furnace having a 5-ton scale top-bottom blowing function. A carbon-containing substance having a particle diameter of 5 to 25 mm and a true specific gravity of 1.60 and having thermal degradability was used. The operation was carried out by blowing the top and bottom at a bottom blown oxygen flow rate of ³ Nm ³ / min and a top blown oxygen flow rate of 17 Nm ³ / min. During the operation, the slag forming was controlled by adjusting the lance height, and the apparent specific gravity of the slag was 1.20 ±
It was adjusted to a range of 0.05 and used as an example. In addition, the apparent specific gravity of the slag was adjusted to a range of 1.80 ± 0.10, which was used as a comparative example.
Table 2 shows the addition yield (carbon material yield) of the added amount of carbon-containing substance.
Shown in

[0023]

[Table 2]

The thermal decay property of the carbon-containing substance was confirmed by taking a sample of slag during blowing and measuring the particle size distribution of the residual carbon material. FIG. 2 shows the particle size distribution of the residual carbon material in the slag. From the terminal velocity of the carbon material with a true specific gravity of 1.6 and the exhaust gas flow velocity in the furnace, carbon material with a particle size of 3 mm or less can be scattered, but in Test No. 1 (Example), approximately 90% of the residual carbon material
Is included in this range. On the other hand, Comparative Example (Test No. 2)
In the figure, the carbon-containing material was thermally collapsed and became finer, but as a whole, shifted to the larger diameter side as compared with Test No. 1 (Example). This is because the entrainment in the slag does not progress enough,
It is considered that small-diameter carbon material was scattered.

From Table 2, it can be seen that in Examples (Test No. 1) operated within the scope of the present invention, the addition yield of the carbon-containing substance was as high as 99%, whereas Comparative Examples outside the scope of the present invention were obtained. (Test No.
In 2), the addition yield of the carbon-containing substance is extremely low at 88%. Thus, by adjusting the apparent specific gravity of the slag in the furnace to be smaller than the true specific gravity of the added carbon-containing material, entrainment of the carbon-containing material into the slag is promoted, and a high carbon material yield can be achieved.

[0026]

According to the present invention, a high addition yield of the carbon-containing substance can be obtained, and a great industrial effect can be obtained. In the present invention, the apparent specific gravity of the slag present in the furnace is made smaller than the true specific gravity of the carbon-containing material to obtain a high addition yield of the carbon-containing material. The type of the contained material is predetermined, and it is necessary to adjust the specific gravity of the slag in accordance with the specific gravity of the carbon-containing material. Adjustment, adjustment of slag components, and the like are conceivable.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a carbon material scattering rate and an apparent specific gravity of slag.

FIG. 2 is a graph showing a particle size distribution of a residual carbon material in slag.

Claims (3)

[Claims] 1. A method for smelting and reducing chromium ore by adding chromium ore and a carbon-containing substance to a converter type smelting reduction furnace having a top and bottom blowing function, and supplying oxygen by top and bottom blowing to melt a chromium ore. In the method of smelting reduction of chromium ore, the apparent specific gravity of the slag present in the converter type smelting reduction furnace is adjusted to be smaller than the true specific gravity of the carbon-containing material. 2. The method for smelting and reducing chromium ore according to claim 1, wherein the carbon-containing substance having a particle size of 3 mm or more is used. 3. The method for smelting reduction of chromium ore according to claim 1, wherein a thermally decayable carbon-containing material is used.