JPH0768574B2 - Metal oxide smelting reduction method and smelting reduction furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention uses a top blowing type smelting furnace to melt carbonaceous solid fuel (for example, coke) into melts (for example, hot metal and molten slag) in the furnace. Is charged, and the carbonaceous solid fuel is burned by spraying an oxidizing gas from a top-blown lance, and a solid raw material containing oxides of the smelting target metal charged into the furnace by the heat of combustion (for example, iron ore). , Manganese ore, chromium ore, etc.) and a smelting reduction method and a smelting reduction furnace for advancing the reduction reaction of the oxide of the smelting target metal.

[Background of the Invention and Prior Art]

To the molten slag on the molten metal in the top-bottom blow-type smelting furnace (converter type reactor), the solid oxide raw material containing the smelting target metal and the carbonaceous solid fuel are charged from the top of the furnace and melted. The carbonaceous solid fuel is burned by blowing the oxidizing gas from the top blowing lance while applying the bottom blowing gas agitation to the metal,
The smelting reduction method in the top-and-bottom blow smelting furnace, in which the oxide raw material is melted and reduced by this heat of combustion, is important as a method for smelting reduction smelting of iron ore, manganese ore, and chromium ore without depending on electric power. Is being watched.

The productivity of the smelting reduction method in this upper-bottom blowing smelting furnace is the solid oxide raw material containing the smelting purpose metal (hereinafter sometimes abbreviated as solid oxide raw material) and the solid added as necessary. It is determined by the dissolution rate of the slag material and the reduction rate of the target metal oxide in the oxide. For this reason, (1). Efficient combustion of carbonaceous solid fuel injected into the furnace, (2). To make efficient use of this combustion heat for the combustion and melting of solid oxide raw materials, (3). It is important to actively supply the unreduced oxide to the so-called reaction site where the reduction reaction of the target metal oxide proceeds.

Conventionally, in order to efficiently burn the carbonaceous solid fuel of the above (1), it has been proposed to provide a large number of gas ejection ports at the tip of the upper blowing lance. In other words, the jet of oxidizing gas is sprayed from a large number of gas jets onto the molten slag in a jet pattern that spreads divergently, thereby forming a fire spot over a relatively large area.

Further, mainly in the above (2) and (3), since the stirring of the contents meets the purpose thereof, the gas stirring from the bottom blowing nozzle is most commonly performed as a method of performing this stirring. Further, a method has also been proposed in which a side blowing lance is provided on the side wall of the reaction furnace to assist the gas stirring.

[Problems to be solved by the invention]

In the above-mentioned conventional technique in which the gas is blown from the side-blowing and bottom-blowing nozzles while blowing the oxidizing gas from the top blowing lance, the oxidizing gas is such that the gas blown for stirring reacts with the elements in the molten metal to generate heat. If it is not (for example, oxygen or oxygen-enriched air), the amount of heat supplied to the molten metal will be insufficient, even if the stirring strength is increased so as to promote heat transfer from the molten slag to the molten metal. The smaller the furnace, the more marked the temperature drop of the molten metal. In such a metal oxide smelting reduction method, if the temperature of the molten metal is controlled to be constant, the supply rate of the solid oxide raw material is decreased, or the flow rate of the oxidizing gas injected from the top blowing lance is decreased. Therefore, it is inevitable to raise the temperature of the molten metal by increasing the fuel consumption and increasing the combustion amount of carbonaceous solid fuel. As a result, productivity is reduced and the amount of refractory erosion is increased.

On the other hand, in the smelting reduction method in which an oxidizing gas is blown at the top and bottom,
The oxidizing gas blown from the bottom-blown lance oxidizes the elements in the molten metal, and the amount of heat generated by this oxidation can be imparted to the molten metal, so that the temperature drop of the molten metal can be prevented. In order to prevent damage, it is necessary to blow a cooling gas (eg LPG) together with the oxidizing gas. Further, when a metal such as chromium having a strong affinity for oxygen is melt-reduced, a part of the reduced chromium is reoxidized, so that there is a limit to improvement in productivity.

The present invention is intended to solve such problems, and an object thereof is to provide a method and a smelting furnace for carrying out smelting reduction with high productivity.

[Means for solving problems]

The gist of the present invention, which is intended to achieve the above-mentioned object, is that carbonaceous materials are introduced from the opening in the upper part of the furnace on the molten metal surface of the molten metal and slag charged in the upper blowing converter type reactor vessel. After the solid fuel is charged, the carbonaceous solid fuel is burned by spraying the oxidizing gas from the upper blowing lance, and the solid raw material containing the oxide of the smelting target metal is charged into the furnace through the opening in the upper part of the furnace. In a smelting reduction method of advancing a dissolution and a reduction reaction of the metal oxide for smelting, an oxidizing gas is supplied toward a slag layer through a side wall of the container, and at the same time, induction heating stirring is applied to the molten metal. And Then, as a smelting furnace suitable for carrying out this method, the upper blowing converter type reaction vessel main body is configured to be divided into an upper furnace body and a lower furnace body at a position where contents exist, and It is intended to provide a metal oxide smelting reduction furnace in which a side blowing lance is installed on a side wall and a low-frequency induction heating device is installed on a lower furnace body.

That is, according to the present invention, an oxidizing gas is blown from the top-blown lance and the side-blown lance to accelerate the smelting reduction of the smelting target metal oxide in the molten slag, and at the same time, the molten metal is stirred by induction heating. Is characterized by performing heating and stirring without reoxidizing the smelting target metal, thereby improving productivity.

FIG. 1 shows an example of a top blowing converter type reaction vessel suitable for applying the method of the present invention. The smelting furnace having the opening 1 at the upper portion is such that the upper furnace body 2a and the lower furnace body 2
It is configured so that it can be divided vertically into 2b. When the refractory material of the upper furnace body 2a is melted and the refractory material needs to be replaced by this upper and lower division, the lower furnace body 2b is not cooled,
Moreover, it is possible to replace the repaired upper furnace body 2a without requiring a long time. Therefore, as shown in the figure, it is desirable that the slag layer 6 does not substantially come into contact with the lower furnace body 2b and the slag layer 6 comes into contact with the furnace wall of the upper furnace body 2a. ， It is desirable to set the upper and lower division positions so that such operations can be performed.

A side blowing lance 4 is provided on the side wall of the upper furnace body 2a, and an oxidizing gas is blown into the furnace together with the upper blowing lance 3 inserted from the opening 1. It is desirable that the position of the lateral blowing lance 4 be an in-layer position of the slag layer 6, but it may be an upper and lower position slightly deviated from the slag layer 6. On the other hand, a low-frequency induction heating device 8 is installed in the lower furnace body 2b. In the illustrated example, the center of the bottom of the lower furnace body 2b is formed in a reduced diameter portion projecting downward, and a coreless low frequency induction heating device 8 similar to the crucible type low frequency induction furnace is formed around the reduced diameter portion. It is installed. By energizing the low-frequency induction heating device 8, the molten metal 5 existing in the lower furnace body 2b can be induction-heated and simultaneously agitated. According to this, damage to the refractory around the bottom blowing nozzle, which is found in a smelting furnace in which gas is blown to stir molten metal, can be avoided and the life of the furnace can be improved. In FIG. 1, 7 is a thermometer and 9 is a water-cooled cooler for preventing overheating of the upper blowing lance 3.

In the smelting furnace as shown in Fig. 1, the molten pig iron was charged, the coke as the carbonaceous solid fuel and the chromium ore as the solid oxide raw material were charged through the opening 1 at the upper part of the furnace, and the slag material was appropriately charged. The method of the present invention will be specifically described below by taking the case of carrying out the smelting reduction of chromium ore as an example.

At the start of smelting, first, the hot metal melted in an electric furnace or the like is charged into the reaction vessel, and then coke and slag material are charged through the opening 1 in the upper part. Next, an oxidizing gas such as oxygen gas is blown from the upper blowing lance 3 and the side blowing lance 4 toward the molten slag 6 to burn the coke in the slag and on the slag bath surface, and at the same time perform low-frequency induction heating of the hot metal. To do. When hot metal is heated by low-frequency induction, magnetic field lines are generated in the hot metal, and due to the action, the hot metal vigorously stirs and moves, so heat transfer from the molten slag bath to the hot metal due to the combustion of coke. Is promoted. This effect
In addition to the hot metal heating effect of low-frequency induction, the temperature of the charged hot metal is rapidly raised.

When the hot metal temperature reaches a predetermined value, charging of the chromium ore is started, and the charged chromium ore is melt-reduced. When the chrome ore is charged batchwise or continuously,
Along with this, coke is also fed batchwise or continuously to replenish the carbon source necessary for temperature rise and reduction. In addition, slag material is also added as needed. During the smelting reduction, the coke is burned by the oxygen gas supplied from the top-blown and side-blown lances, and due to the heat of combustion, the chrome ore and slag material charged are melted and the coke-molten slag interface mainly advances. The amount of heat required for the smelting reduction reaction of chromium oxide and iron oxide is covered. Metallic chromium and metallic iron produced by the smelting reduction reaction pass through the slag and settle in the hot metal. For this reason, the chromium concentration in the hot metal increases as the smelting reduction time elapses. Since the freezing point of the hot metal increases as the chromium concentration in the hot metal increases, it is necessary to maintain the hot metal temperature above a certain level.

Therefore, the low-frequency induction heating of the hot metal is performed while adjusting the low-frequency output appropriately so that the temperature of the hot metal can be measured by the thermometer 7 and managed at a certain level or higher. As a result, there is no need to wait for the chromium ore to be charged due to the decrease in the hot metal temperature, and the chromium ore can be charged at regular intervals or continuously. Furthermore, the hot metal temperature and hot metal components can be made uniform by the stirring action of the hot metal due to the low frequency induction.

When a predetermined amount of chromium ore was charged, the charging of ore and slag was stopped, but oxygen gas injection from the top and side blowing lances and low-frequency induction heating of the hot metal were continued, and finish reduction was performed. To do. After carrying out finish reduction for a set time, the acid transfer is stopped and the tapping and slag are carried out. However, if necessary, only the slag is discharged to the outside of the furnace, and the hot metal is dephosphorized and desulfurized. You can also do it. Even when performing dephosphorization and desulfurization treatment, low-frequency induction heating of the hot metal can prevent temperature drop when introducing flux for dephosphorization and desulfurization treatment, and manage the hot metal temperature to a temperature level suitable for the treatment. it can. Furthermore, since the hot metal is strongly stirred, the processing time can be shortened.

Examples of the present invention will be given below.

Example 1 Using a 30 ton scale smelting furnace with a low frequency induction heating device installed at the bottom of the furnace as shown in FIG. 1, a total of four are arranged at 90 ° intervals in the circumferential direction of the furnace. While blowing air at a flow rate that can prevent blockage of the lance tip from the side blowing lance 4, the temperature was 1420 ° C, Cr: 10.5%, C: 3.4%, Si: 0.3%, M
21.1 tons of chromium-containing hot metal having chemical composition values of n: 0.4%, P: 0.02%, S: 0.02%, and then 2.0 tons of coke with chemical composition values shown in Table 1 below, Quick lime and silica stone, which have the chemical composition values shown in the table, were allotted so that the basicity of the molten slag produced was 1.0, and a total of 2.5 tons was charged into the furnace through the opening 1 at the top of the furnace, and then from the top blowing lance 3. Is 72
The nm ³ / hr of flow rate of the oxygen gas, also from the four horizontal lance, with spraying each bath surface to 220Nm ³ / hr · lance flow rate of the oxygen gas, subjected to low-frequency induction heating of the hot metal Then, the temperature of the chromium-containing hot metal was raised to 1600 ° C to produce slag.

Immediately after the temperature of the hot metal was completed, the coke and the basicity of the molten slag were added to the chromium ore semi-reduced pellets (Cr reduction rate: 47%, Fe reduction rate: 84%) with the chemical composition values shown in Table 1. always
Within the range of 0.90 to 1.05 and the MgO + Al ₂ O ₃ in the slag is 40 to 42
While adding the slag-making material so as to be maintained in the range of 1.0%, 21.0 tons of the total amount of pellets were charged in 1.4-ton intervals at 5-minute intervals. At this time, while measuring the hot metal temperature with a thermometer, the output of the low-frequency induction heating device was appropriately adjusted so that the temperature was always maintained in the range of 1580 to 1640 ° C.

After the completion of all charging, the amount of oxygen in the upper blowing lance 3 was reduced to 1/2, and after blowing for 5 minutes, the blowing of oxygen was stopped and the furnace was tilted to discharge the molten slag and the hot metal. As a result, Cr: 24.9%, C:
7.0%, Si: 0.2%, P: 0.027%, S: 0.036% chromium-containing hot metal 3
Got 1.1 tons.

Example 2 The same reaction vessel as in Example 1 was used, and in this vessel, C: 4.3%, Si: 0.01%, S: 0.021%, P: 0.03 produced by preheating.
While leaving 5.3 tons of 4% hot metal as the seed water, 0.5 tons of coke having the chemical composition values shown in Table 2 below was put into the hot metal melt through the upper opening, and then from the top blowing lance to 72
The flow rate of oxygen gas nm ³ / hr, also, four lateral blowing carbon coke and in pig iron bath surface in by blowing 220Nm ³ / hr · lance flow rate of the oxygen gas respectively bath surface from the lance Burned, low-frequency induction heating is performed, and the temperature of the hot metal is 1500 ℃.
The temperature was raised to.

Immediately after the temperature rise of the hot metal was completed, coke was added to the self-fluxing pellets having the chemical composition values shown in Table 2 and the total amount of 39 tons of the pellets was charged at 1.5 ton intervals every 6 minutes. During the smelting reduction, the hot metal temperature was maintained in the range of 1490 to 1530 ° C while the output of the low frequency induction heating device was adjusted appropriately.

After the completion of all charging, the amount of oxygen fed from the top and side blowing lances was reduced to 1/2 and the oxygen was blown off.
The furnace was tilted to leave 5 tons of hot metal, and everything else was discharged outside the furnace. As a result, C: 4.4%, Si: 0.01%, S: 0.026%, P: 0.033
26.5 tons of% hot metal was obtained.

Comparative Example An attempt was made to perform smelting reduction of chromium ore semi-reduced pellets under substantially the same conditions as in Example 1 except that low frequency induction heating of hot metal was not performed. At this time, in order to maintain the hot metal temperature in the range of 1580 to 1640 ° C, while the temperature was low, charging of the pellets was withheld until the temperature reached this temperature. As a result, it took 103 minutes to complete the charging of the chromium ore semi-reduced pellets with a total amount of 21.0 tons, and the productivity was deteriorated as compared with Example 1.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a smelting furnace suitable for carrying out the method of the present invention. 1 …… Upper opening, 2a …… Upper furnace body 2b …… Lower furnace body, 3 …… Top blowing lance 4 …… Horizontal blowing lance, 5 …… Hot metal 6 …… Melting slag, 7 …… Thermometer 8 …… Low frequency induction heating device

Claims (2)

[Claims] 1. A carbonaceous solid fuel is charged from an opening in the upper part of the furnace onto the molten metal surface of a molten metal and slag charged in a top-blown converter type reactor vessel, and is oxidized from a top-blown lance. Gas is sprayed to burn the carbonaceous solid fuel, and the solid raw material containing the oxide of the refining target metal, which is charged into the furnace through the opening in the upper part of the furnace, is dissolved and the reduction reaction of the refining target metal oxide is performed. In the smelting reduction method for advancing, the oxidative gas is supplied toward the slag layer through the side wall of the container, and at the same time, the molten metal is subjected to low-frequency induction heating and stirring, and the smelting reduction method for the metal oxide. 2. The upper blowing converter type reactor vessel main body is configured to be divided into an upper furnace body and a lower furnace body at a position where contents exist, and
A smelting reduction furnace for metal oxides in which a side blowing lance is installed on the side wall of the upper furnace body and a low-frequency induction heating device is installed on the lower furnace body.