JPH0237282A - Method of removing molten iron from rockwool electric furnace - Google Patents

Abstract

PURPOSE:To protect the bottom of the furnace by inclining the bottom of the furnace such that it becomes lower from the molten iron removal opening toward the opposite side for the purpose that only the molten iron above the level of the molten iron removal opening is discharged through said opening. CONSTITUTION:When the molten iron B is to be removed, the whole furnace is tilted by means of a tilting cylinder 8 to lift the molten iron removal opening 4 and incline the bottom of the furnace such that it becomes lower from the molten iron removal opening 4 toward the opposite side. Then, the molten iron removal opening 4 is opened by removing the closure lid 5 to discharge the molten iron B from the furnace bottom through said opening 4. As the molten iron B is discharged, that part of the molten iron B which is above the level of the molten iron removal opening 4, but the rest of the molten iron below that level stays in the furnace. On account of the remaining molten iron on the furnace bottom, the furnace bottom is protected from the rockwool material getting in contact with the carbon lining on the furnace bottom.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for removing hot metal in an electric rock wool melting furnace.

[Conventional technology]

Rock wool is manufactured by melting its raw material in a melting furnace, tapping the melted raw material into a cotton mill, and making it into fibers by blowing or spinning. Traditionally, andesite, basalt, etc. have been used as raw materials for rock wool, but recently, in order to stabilize the quality, metal scouring slag, mainly blast furnace sujig, is used as the main raw material, and chemical components are added to it. Silica stone, dolomite, limestone, etc. are added as auxiliary raw materials for the preparation of

By the way, an electric melting furnace is generally used as a melting furnace for rock wool raw materials, but when a rock wool raw material whose main component is a raw material containing iron oxides such as blast furnace slag is melted in this electric melting furnace. In the process, part of the iron oxide in the rock wool raw material reacts (reduction reaction) with the carbon electrode and the carbon lining material on the inner surface of the furnace in the molten W state to produce pig iron, which is stored as hot metal at the bottom of the furnace. . In the above-mentioned electric melting furnace, the tap from which the molten rock wool raw material is tapped into the cotton mill is provided at a certain level above the bottom of the furnace.
The amount of hot metal stored at the bottom of the furnace increases as raw materials are repeatedly charged into the furnace and melted. At the same time, the quality of the rock wool that is produced by the hot water that is tapped into the cotton mill will change.

Therefore, in an electric melting furnace that melts rock wool raw materials containing iron oxides, it is necessary to remove the hot metal accumulated at the bottom of the furnace from the furnace before the bath surface reaches the outlet for the molten raw material. Therefore, in the above-mentioned melting furnace, a hot metal extraction port is provided separately from the tap for the molten raw material, and the hot metal accumulated at the bottom of the furnace is periodically extracted from the hot metal extraction port.

Conventionally, this hot metal extraction port was provided at the same level as the hearth bottom or at a position lower than the hearth bottom (Japanese Patent Laid-Open No. 62-153
140 and Utility Model Application Publication No. 63-46437).

[Problem to be solved by the invention]

However, conventionally, as mentioned above, the hot metal extraction port was provided at the same level as the furnace bottom or at a position lower than the furnace bottom, so that when the hot metal was extracted, the hot metal accumulated at the furnace bottom was completely removed. Another problem was that the bottom of the melting furnace was severely eroded.

This erosion of the furnace bottom was discovered when the applicant dismantled an electric melting furnace that was used to melt rock wool raw materials containing iron oxides. The lining had been eroded to the point where it was almost completely gone.

Therefore, we investigated the cause of the corrosion of the furnace bottom and found that
It has been found that this corrosion of the furnace bottom is caused by the molten rock wool raw material in the furnace coming into contact with the carbon lining material at the furnace bottom, and iron oxides, that is, carbon unsaturated iron in this molten raw material, causing a reduction reaction. It was. Conventionally, the hot metal stored at the bottom of the furnace is completely removed, so after the hot metal is removed, the rock wool raw material comes into direct contact with the carbon lining material at the bottom of the furnace. Since saturated iron absorbs carbon from the carbon lining of the furnace and undergoes a reduction reaction, the carbon lining at the bottom of the furnace is eroded. This corrosion of the carbon lining material rarely occurs in electric scouring furnaces that add a reducing agent (coke) to the charging raw material, but in electric rock wool melting furnaces that melt rock wool raw materials, Erosion of the carbon lining material is significant because no reducing agent is added to the raw material.

If the hot metal stored in the furnace bottom is completely removed as in the conventional method, the erosion of the furnace bottom lining material due to the reduction reaction of the carbon-unsaturated iron will be repeated every time the stored hot metal is removed. As a result, the furnace bottom lining material corroded significantly in a short period of time, which shortened the useful life of the melting furnace.

The present invention was made in view of the above-mentioned circumstances, and its purpose is to prevent the rock wool raw material from coming into contact with the carbon lining material at the hearth bottom even after the hot metal stored at the hearth bottom is removed. To provide a method for removing hot metal from an electric melting furnace for rock wool, which protects the bottom of the furnace from corrosion and reduces corrosion of the carbon lining material at the bottom of the furnace.

[Means to solve the problem]

In order to achieve the above object, the present invention lowers the bottom of the melting furnace from the hot metal extraction port side toward the opposite side by tilting the melting furnace in a direction in which the hot metal extraction port side rises when hot metal is extracted. By tilting it so that only the hot metal above the level of the hot metal extraction port flows out from the hot metal extraction port,
The hot metal below the above level is left in the furnace.

[Effect]

In this way, even if the hot metal stored at the hearth bottom is extracted, the hot metal below the level of the hot metal extraction port will remain in the furnace, making it possible to cover the hearth bottom with a layer of hot metal remaining above. Because of this, even after the hot metal stored at the hearth bottom is extracted, the hot metal left at the hearth bottom can protect the hearth bottom so that the rock wool raw material does not come into contact with the carbon lining material at the hearth bottom. , to prevent the carbon unsaturated iron in the molten rock wool raw material from absorbing carbon from the carbon lining material at the bottom of the furnace and causing a reduction reaction.
Erosion of the carbon lining material at the hearth bottom can be reduced.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

First, to explain the structure of an electric melting furnace for melting rock wool raw materials, in Fig. 1, 1 is the furnace body of the electric melting furnace;
Reference numeral 2 denotes a furnace lid, and the bottom and inner wall surface of the furnace body 1 are lined with carbon lining material 1a.

Reference numeral 3 denotes a tap hole for the molten rock wool raw material provided on the furnace wall of the furnace body 1, and 4 is a hot metal extraction port provided on the furnace wall on the opposite side from the tap hole 3. The hot metal extraction port 4 is provided at a position slightly higher than the bottom of the furnace and sufficiently lower than the tapping port 3. Note that the tap 3 is provided with a sprue cover 3a that can be opened and closed, and the hot metal extraction port 4 is closed with a closing mud 5. Further, the furnace body 1 is supported on a pedestal 6 via a lock gear 7 so as to be tiltable. This lock gear 7 consists of a horizontal gear 7a provided on the pedestal 6, and an arc gear 7b provided on the lower surface of the furnace body l and meshing with the horizontal gear 7a. It is designed to be tilted by.

A plurality of carbon electrodes 9 are inserted into the furnace through the furnace M2, and each electrode 9 is supported by an electrode holding arm 11 that is movably supported by a vertical mast 10 installed outside the furnace body.
is maintained. Further, 12 and 13 are main raw material and auxiliary raw material charging pipes for charging rock wool raw materials into the furnace, and these raw material charging pipes 12 and 13 are attached to the furnace lid 2.

A hopper 12a is provided at the upper part of the main raw material charging pipe 12, and a raw material containing iron oxide, which is the main raw material for rock wool, such as blast furnace slag (here, molten slag) is transferred to a ladle 12a.
The raw material is transported by the hopper 11a and charged into the furnace through the main raw material charging pipe 11. Further, 15 is an auxiliary raw material storage tank installed above the furnace, 16 is an auxiliary raw material supply device that supplies the auxiliary raw material in this storage tank 15 to the auxiliary raw material charging pipe 13, and the auxiliary raw material charging pipe 13 is connected to the joint 13a. Through the auxiliary raw material supply device 1
6 and is detachably connected.

To explain the operation of this electric melting furnace, the rock wool raw materials are melted by charging the rock wool raw materials (main raw materials and auxiliary raw materials) into the furnace and applying electricity to the carbon electrode 9. In this case, if a large amount of molten blast furnace slag is charged as the main raw material from the start of operation of the electric melting furnace, there is a risk that cracks will occur in the carbon lining material 1a at the bottom of the furnace due to thermal shock.
At the start of operation, cooled blast furnace slag grains are charged as part or all of the main raw material, and carbon material (coke) for energization is added to the charged raw material to gradually melt the charged raw material. desirable. However, even with this method, if the molten rock wool raw material A is in direct contact with the carbon lining material 1a at the bottom of the furnace, iron oxides in the molten raw material A, that is, carbon unsaturated iron, will be contained in the carbon at the bottom of the furnace. In order to absorb carbon from the lining material 1a and cause a reduction reaction, the carbon lining material 1a at the bottom of the furnace is eroded. Therefore, in this embodiment, prior to charging the rock wool raw material, crushed pig iron particles having a carbon content of 3.5% or more are spread on the bottom of the furnace, and the rock wool raw material is charged on top of this. If the crushed particles of pig iron are spread on the bottom of the furnace in this way, the crushed particles of pig iron will melt and become molten pig iron, and the bottom of the furnace will be covered with a layer of this molten pig iron, so that the iron oxides in the molten raw material A will be absorbed into the furnace. It is possible to prevent the carbon lining material 1a at the bottom from absorbing carbon and causing a reduction reaction, and therefore the carbon lining material 1a at the bottom of the furnace is not eroded. After melting the rock wool raw material charged into the furnace, the sprue cover 3b is opened and the molten raw material A in the furnace is tapped out from the tap 3 to a cotton mill (not shown). The molten raw material A is discharged by connecting the auxiliary raw material charging pipe 13 to the joint 13a.
At this point, the melting furnace is separated from the auxiliary raw material supply device 16, and the entire melting furnace is tilted by the tilting cylinder 8 as shown by the chain line in FIG. Note that for tapping this molten raw material A, electricity is continued to be applied to the electrode 9.1. This is carried out while maintaining the temperature of the molten raw material A.

By the way, when the above operation is repeated, a part of the iron oxide in the rock wool raw material reacts (reduction reaction) with the carbon electrode 9 and the carbon lining material 1a of the furnace wall in a molten state, and the resulting pig iron is transferred to the furnace as molten pig iron. In order to prevent the molten pig iron B stored at the bottom of the furnace from being discharged to the cotton mill together with the rock wool raw material, the molten pig iron B stored at the bottom of the furnace must be heated so that its bath surface reaches the tapping port 3. It is necessary to remove it from the furnace first.

Therefore, in this embodiment, the hot metal B stored at the bottom of the furnace is extracted as follows. First, when removing hot metal B,
The entire melting furnace is tilted by the tilting cylinder 8 in the direction in which the hot metal extraction port 4 side rises (the same direction as the tilting direction when tapping the rock wool raw material), and the bottom of the melting furnace is tilted as shown in FIG. It is sloped so that it becomes lower from the extraction port 4 side to the opposite side. Thereafter, the blocking mud 5 blocking the hot metal extraction port 4 is removed to open the hot metal extraction port 4, and the hot metal B at the bottom of the furnace is flowed out from the hot metal extraction port 4. When the hot metal B in the furnace bottom flows out from the hot metal extraction port 4 while the bottom of the melting furnace is tilted downward from the hot metal extraction port 4 side to the opposite side, the hot metal extraction port 4 The hot metal above the level flows out from the hot metal outlet 4, while the hot metal below the level remains in the furnace as shown in FIG.

Note that this extraction of the hot metal B is performed after the molten rock wool raw material A in the furnace is tapped out, and after the extraction of the hot metal B, the hot metal extraction port 4 is again closed with the blocking mud 5, and the melting furnace is closed. is returned to the state shown in FIG. 1, and the next rock wool raw material is melted. However, in this case, hot metal extraction port 4
Since the bottom of the furnace is covered with hot metal B that remains in the furnace without flowing out, there is no need to cover the bottom of the furnace with crushed pig iron particles as at the start of operation.

However, when such hot metal is extracted, even if the stored hot metal B at the hearth bottom is extracted, the hot metal B below the level of the hot metal extraction port 4 remains in the furnace, so the hearth bottom is placed above it. It can be covered by a layer of remaining hot metal. According to the hot metal extraction method described above, even after the hot metal stored at the hearth bottom is extracted, the hot metal B left at the hearth bottom protects the hearth bottom so that the rock wool raw material does not come into contact with the carbon lining material at the hearth bottom. Therefore, even after the hot metal is removed, iron oxides in the molten rock wool raw material, that is, carbon unsaturated iron, can be prevented from absorbing carbon from the carbon lining material 1a at the bottom of the furnace and causing a reduction reaction. Since this can be prevented, corrosion of the carbon lining material 1a at the bottom of the furnace can be reduced and the service life of the melting furnace can be extended. In addition, since the hot metal B stored at the bottom of the furnace is made by iron oxide in the rock wool raw material reacting with carbon to become pig iron, the hot metal in contact with the bottom of the furnace reacts with the carbon lining material 1a. Very rarely. In addition, hot metal B is necessary to protect the bottom of the furnace.
A layer thickness of about 25 to 75,111 m is sufficient, and therefore, the tilting angle of the melting furnace at the time of hot metal withdrawal may be set to an angle that leaves an amount of hot metal at the bottom of the furnace that provides the above layer thickness.

In the above embodiment, the hot metal extraction port 4 is opened after the melting furnace is tilted, and the hot metal B flows out from the hot metal extraction port 4. The melting may be performed while opening the melting furnace and tilting the melting furnace.

In addition, in the above embodiment, the molten rock wool raw material A in the furnace
Although the hot metal is extracted after the rock wool is tapped, the hot metal can also be extracted while the rock wool raw material is being melted in the furnace. Furthermore, in the above embodiment, the hot metal extraction port 4 is provided at a position slightly higher than the furnace bottom, but the hot metal extraction port 4 may be provided at the same level as the furnace bottom or at a position lower than the furnace bottom. If the melting furnace is tilted in the direction in which the hot metal extraction port side rises and the hot metal is extracted, the molten metal below the level of the hot metal extraction port can be left in the furnace.

〔Effect of the invention〕

According to the hot metal extraction method of the present invention, even if the hot metal stored in the furnace bottom is extracted, the hot metal below the level of the hot metal extraction port remains in the furnace. You can leave it there. Therefore, even after the hot metal stored at the hearth bottom is removed, the hot metal left at the hearth bottom can protect the rock wool raw material from coming into contact with the carbon lining material at the hearth bottom. It is possible to prevent carbon unsaturated iron in the rock wool raw material from absorbing carbon from the carbon lining material at the bottom of the furnace and causing a reduction reaction, thereby reducing corrosion of the carbon lining material at the bottom of the furnace.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of an electric melting furnace in a raw material melting state and a hot metal extraction state, showing an embodiment of the present invention. 1.1. Furnace body, 1a... Carbon lining material, 3... Tap tap, 4... Hot metal extraction port, 5... Blocking mud, 6...
Tilting cylinder, A...molten raw material, B...hot metal.

Claims (1)

[Claims] A method for extracting hot metal stored in the bottom of an electric melting furnace for melting rock wool raw material containing iron oxide from a hot metal extraction port provided in the melting furnace separately from a tap for the molten raw material,
When extracting hot metal, the melting furnace is tilted in a direction in which the hot metal extraction port side rises, thereby tilting the bottom of the melting furnace downward from the hot metal extraction port side toward the opposite side, thereby lowering the level of the hot metal extraction port. A method for removing hot metal in an electric melting furnace for rock wool, characterized in that only the hot metal above the level flows out from the hot metal extraction port, and the hot metal below the level remains in the furnace.