JPH0723494B2 - Method and apparatus for refining molten metal - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for refining molten metal and an apparatus therefor, and more specifically, a gas containing oxygen is blown from a top blowing lance and a stirring gas is bottom blown. Method and apparatus for supplying oxygen, carbonaceous material and metal oxide to molten iron in this container by using a metallurgical furnace capable of being blown from a tuyere, and performing melt reduction of the metal oxide with high efficiency and economically Regarding

[Conventional technology]

When melting stainless steel in a top-bottom blow converter in recent years, without using expensive ferrochrome, inexpensive primary energy, for example, coke as a reducing energy to smelt and reduce chromium ore or semi-reduced ore in the converter, Techniques for producing stainless steel or a melt of stainless steel are being developed.

A technique for refining chromium ore or its pre-reduced pellets in a top-bottom blow converter is disclosed in, for example, Japanese Patent Laid-Open No. 60-9814.

Similarly, a technique for producing molten pig iron by smelting reduction of iron ore in a converter is also disclosed in, for example, Japanese Patent Application Laid-Open No. 52-28821.

In these processes, coke or other carbonaceous materials are used as the reduction energy used when smelting ores such as chromium ore and iron ore, so the reduction energy consumption rate is reduced and economical smelting reduction is performed. Therefore, it is necessary to use the heat of combustion of coke and oxygen as effectively as possible. That is, it is important to promote not only the primary combustion represented by the following equation (1) but also the secondary combustion represented by the following equation (2) in the furnace to the maximum extent.

C + 1 / 2O ₂ → CO …… (1) CO + 1 / 2O ₂ → CO ₂ …… (2) However, when the CO ₂ generated by the equation (2) directly contacts the steel bath, the dissociation reaction of the following equation (3) It was difficult to achieve a high secondary combustion rate in the converter because of the occurrence of

CO ₂ + C ( C in steel bath) → 2CO (3) Another problem is that if high secondary combustion is achieved in the metallurgical furnace, the refractory in the furnace will be 2000 due to the combustion in the metallurgical furnace.
It is a high temperature exceeding ℃ and melts.

The life of the refractory depends not only on the FeO concentration in the slag but of course, the refractory above the part where the high temperature combustion gas comes into contact (mainly the part where the slag exists) is significantly melted.

Therefore, it is important to reduce the refractory unit consumption in the metallurgical furnace, extend the life of the furnace and improve the economics of the process.

[Problems to be solved by the invention]

It is an object of the present invention to provide a molten metal refining method and apparatus for solving the above problems.

The present invention uses a metallurgical furnace having a top blowing lance capable of blowing a gas containing oxygen and having a bottom blowing tuyere capable of blowing a gas, and stores molten iron in the metallurgical furnace, and further In order to achieve a high secondary combustion rate and prevent damage to the furnace wall of a metallurgical furnace under high secondary combustion in a method of performing smelting reduction of metal oxide by supplying materials, oxygen and metal oxides. It is a technical subject to obtain the means of.

[Means for solving problems]

The above-mentioned technical problem in the present invention is achieved by the following characteristic means.

That is, the hot metal is charged into the top and bottom blowing metallurgical furnace, the stirring gas is supplied from the bottom blowing tuyere, the refining gas containing the oxidizing gas is supplied from the top blowing lance, and the carbonaceous material and the metal oxide are supplied. In the method for performing smelting reduction, (1) a water-cooled metal panel is used for at least a part of the furnace wall above the molten metal of the upper-bottom blowing metallurgical furnace.

(2) Melt molten metal.

(3) Hot water and / or slag is continuously or intermittently discharged from the holes provided in the furnace belly or the furnace bottom.

It is characterized by

A preferred apparatus for carrying out the method of the present invention is a metallurgical furnace having a bottom blowing tuyere for supplying a stirring gas and an upper blowing lance for supplying an oxidizing gas, and an upper furnace wall of the metallurgical furnace. Is a refining apparatus for molten metal, characterized in that at least a part thereof is made of a water-cooled metal panel, and a tap hole and a slag outlet provided with stoppers are arranged on the furnace belly or bottom.

[Action]

The inventor first used a top-bottom blowing converter having a lance capable of top-blowing a gas containing oxygen and a bottom-blowing tuyere, and used carbon material, oxygen and metal oxides in the molten metal therein. A process for performing smelting reduction of metal oxides by adding Al was tested, and research for achieving a high secondary combustion rate was conducted. As a result, the following things became clear.

That is, in the refining process in the process targeted by the present invention, the reaction proceeds in the state shown in FIG.

That is, the O ₂ jet blown from the upper blowing lance 1 is consumed by combustion with C in the steel bath 7 and combustion with coke 9 in the slag 8 and also with secondary combustion with CO.

In order to achieve a high secondary combustion, it is necessary to enhance the combustion of CO and O ₂ described above, but on the other hand, as mentioned above, the CO generated by combustion with C in the steel bath is O ₂
When the secondary combustion is done by jet, the result is
When CO ₂ comes into contact with the steel bath again, it is dissociated into CO again according to the above formula (3). Therefore, when performing such smelting reduction, it is necessary to blow the O ₂ jet only on the slag 8 and the carbonaceous material 9 in the slag 8 without directly contacting the steel bath. Specifically, it is natural to use the lance itself as a lance having a large nozzle diameter capable of soft blowing, which is well known in steelmaking furnaces, or a porous lance, but in addition to that, set the necessary lance height appropriately, The control is to prevent the O ₂ jet from coming into contact with the molten metal.

However, when smelting reduction is performed by adding ore, carbonaceous material, and oxygen, slag and molten iron increase as the operation progresses. As a result, the control of the lance height is different from that of a normal steelmaking furnace, and it is necessary to gradually raise it, but the slag volume during smelting reduction sometimes exceeds 400 (Kg / t). , The slag top surface becomes too high, making it difficult to keep the lance height above a certain level.

In that case, suspend the operation and tilt the furnace to discharge waste,
Although it is possible to discharge molten iron, it is not preferable because not only the productivity is lowered, but also energy loss such as temperature drop due to interruption occurs.

In addition to these problems, even if a high secondary combustion rate could be achieved, as already mentioned, the high temperature of the atmosphere in the furnace caused the melting of the refractory material above the slag line with which the hot combustion gas comes into contact. There was a problem that the loss became large. Further, as described above, in the smelting reduction operation, the molten iron and the slag molten metal surface height change during the operation, so that merely protecting a part is not actually suitable as a means for protecting the furnace wall of the metallurgical furnace.

Based on these findings, the inventors have achieved a stable high secondary combustion rate during smelting reduction and, at the same time, to prevent melting damage to the furnace wall of the metallurgical furnace during high secondary combustion, as shown in FIG. Melt by a metallurgical furnace with a water-cooled metal panel with at least a part of the furnace wall above the part where molten metal comes into contact, with an opening that allows the discharge of hot metal and slag without tilting A method for reducing smelting was developed.

That is, without stopping the blowing during the smelting reduction blowing,
By providing a molten iron discharge hole 6 capable of discharging molten iron and separately providing a slag outlet 4 for discharging slag, it is possible to appropriately discharge molten iron and slag during operation, and as a result, slag and molten iron can be discharged. It is possible to control the molten metal surface so that a high secondary combustion rate can be achieved.

Furthermore, control is performed so that the slag does not rise above a specific portion of the furnace wall of the metallurgical furnace excessively, and the furnace wall above the normal slag level above the portion where the molten metal comes into contact is made into a water-cooled metal panel 2 and the metallurgical furnace The melting loss of the furnace wall can be almost eliminated. Since the water-cooled panel 2 is covered with the slag itself (slag coating), unlike a conventional refractory wall, there is almost no melting loss even in a high temperature atmosphere due to high secondary combustion.

As shown in FIGS. 1 (a) and 3 (a), the molten iron discharge port 6 has a part of the furnace body expanded so that it can be tapped directly to the bottom of the furnace and tapped from the bottom of that part. The taphole may be attached to the bottom of the furnace as shown in FIG. 3 (b), or the tappipe 6a as shown in FIG. 1 (b) and FIG. 3 (c). May be attached. In the hot metal discharge method, the hot metal may be discharged continuously or the hot metal may be discharged at regular intervals. Also, if necessary, suspend and stop the smelting reduction operation,
It is also possible to carry out tapping and slag, which is of course within the scope of the invention.

The slag outlet 4 is for enabling control of the molten metal surface of the slag, and it is not necessary to discharge all the slag, so it may be attached to the portion where the slag is present in consideration of the compatibility with other devices.

Further, the hot metal discharge port 6 and the slag discharge port 4 can of course be attached at a plurality of positions.

The water-cooled panel 2 may be mounted on the entire surface above the normal slag level, or may be mounted on a part at a certain distance from the slag level, as long as the part to be mounted is determined according to the purpose of operation. The water-cooled panel 2 may be a water-cooled panel structure made of an iron plate or a steel plate, an iron pipe, or a bent pipe of a copper pipe, and a block type in which a cooling water passage is provided in the iron block or the copper block is suitable.

When starting the smelting reduction operation, it is preferable to provide the hot metal charging trough 3 shown in FIG. 1 so that it is not necessary to tilt the metallurgical furnace. Also, during operation, if molten iron and slag are discharged in appropriate amounts, continuous operation is possible, which is advantageous in terms of operation efficiency and thermal efficiency.

As a similar attempt to prevent melting of refractory materials in a metallurgical furnace in a high secondary combustion operation, as described above in Japanese Patent Laid-Open No. 61-67708, a refrigerant is injected from a top blowing lance or refractory materials are used. Attempts have been made to inject a porous refractory into the wall and to inject a gas, etc., but since the top blowing lance needs to change the lance height to control the above-mentioned secondary combustion, at the same time refractory In addition to having difficulty cooling the desired parts of the car, injecting carbonaceous material and water adversely affects secondary combustion.

On the other hand, it is difficult to protect the upper part of all slag levels even when the porous refractory is buried in the refractory and gas is blown into the refractory.

The present invention is intended to control high secondary combustion and prevent melting damage of a metallurgical furnace at that time, and the idea is different from the above invention.

In addition, since refractory is used, it is often disadvantageous in operation when it is cooled because it is greatly damaged by spalling. In any case, it is difficult to suppress melting damage as long as refractory is used.

〔Example〕

4 tons of hot metal was charged into the upper-bottom metallurgical furnace shown in FIG. 1 via a hot metal charging trough 3. 30Nm from top blowing lance from bottom blowing N ₂ through a single pipe tuyeres 5 with 0.5 Nm ³ / min blown ³ / min
At that time, oxygen was blown in to perform smelting reduction operation.

At that time, coke and coal were added during the smelting period (heating period),
By controlling the lance height, secondary combustion was suppressed to about 20%.

Next, when the temperature of the molten metal reached 1550 ° C, coke, iron ore and coal were charged, the smelting reduction operation was performed, and the lance height was controlled so that the secondary combustion was 60 to 70%. On the other hand, 40 to 60 kg so that the temperature of the molten iron becomes 1550 to 1580 ℃
Iron ore was added at a rate of / min.

On the other hand, the furnace wall above the portion where the molten metal comes into contact and above the normal slag level was operated as a water-cooled panel made of copper.

About 2 tons of molten metal (molten iron 7) and about 1 ton of slag were discharged from the slag hole 4 and the molten iron discharge port 6 at the bottom of the furnace for operation.

No damage was observed on the furnace wall above the slag level as a result of continuous operation for about 10 days. The secondary combustion was stable at 60-70% during the operation.

(Comparative Example) The operation was carried out under the same conditions as in the example in the normal upper-bottom blowing converter shown in FIG. 2 on the same scale as in FIG. When the slag increased by 1.5 tons and the molten metal increased by 2 tons, the secondary combustion could not be controlled by controlling the lance height due to the rise of the slag surface, so the operation was interrupted and the molten metal and slag were discharged. After that, the operation was repeated, but the temperature of the molten metal decreased by 50 to 70 ° C at the time of the operation interruption, and it was necessary to raise the temperature again, which was disadvantageous in terms of energy unit productivity.

When the above-mentioned semi-continuous operation was carried out for 70 hours, a part of the refractory material on the furnace wall above the slag level was melted and the operation was interrupted.

Although the smelting reduction of iron ore has been described above as an example, the present invention can naturally be applied to the smelting reduction of chromium ore, manganese ore, and the like.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY As described above, the present invention provides a molten metal with carbonaceous material, oxygen and a metal oxide in a metallurgical furnace having a top blowing lance capable of blowing an oxygen-containing gas and a bottom blower mouth capable of blowing a stirring gas. The energy consumption rate can be reduced by stably achieving high secondary combustion in the process of smelting and reducing metal oxides, and the melting loss of the metallurgical furnace furnace during the operation of high secondary combustion can be achieved. Therefore, it is possible to improve the equipment productivity by reducing the repair frequency of the metallurgical furnace, and to reduce the equipment cost per product unit.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of the present invention, FIG. 2 is an explanatory view showing a smelting reduction technology by a conventional top-bottom blowing converter, and FIG. 3 is an embodiment of a molten metal discharge hole of the present invention. It is a fragmentary sectional view of the metallurgical furnace shown. 1 …… Top blowing lance 2 …… Water cooling panel 3 …… Molten iron charging trough 4 …… Dust outlet 5 …… Bottom blower mouth 6 …… Molten iron discharge port 7 …… Molten iron 8 …… Slag 9 ...... Coke 10 ...... Refractory furnace wall

Front page continuation (72) Inventor Tetsuya Fujii 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Technical Research Division

Claims (3)

[Claims] 1. A top-bottomed metallurgical furnace is charged with molten pig iron, a stirring gas is supplied from a bottom-blown tuyere, and a refining gas containing an oxidizing gas is supplied from a top-blown lance to remove carbonaceous materials and metal oxides. In the method of performing smelting reduction by supplying, a water-cooled metal panel is used for at least a part of the furnace wall above the portion of the metallurgical furnace where the hot metal comes into contact, and the molten metal is melted to form a furnace belly continuously or intermittently. Alternatively, a molten metal refining method is characterized in that hot water is discharged and / or slag is discharged from an opening provided in the bottom of the furnace. 2. A metallurgical furnace provided with a bottom blown tuyere for supplying a stirring gas and a top blow lance for supplying an oxidizing gas.
At least a part of an upper furnace wall of the metallurgical furnace is composed of a water-cooled metal panel, and a molten metal refining apparatus is provided with a tap hole and a slag port provided with stoppers on a furnace belly or a furnace bottom. 3. The apparatus for refining molten metal according to claim 2, further comprising an opening portion above the slag hole of the reaction vessel, into which molten iron can be charged.