JPS6134488B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal magnesium manufacturing apparatus,
In particular, the present invention relates to a metal magnesium manufacturing apparatus including a closed electric furnace.

A method for producing magnesium by an electrothermal high-temperature reduction method, in which a substance containing magnesium oxide is reacted with a reducing agent in the presence of molten slag to produce magnesium under reduced pressure, has already been carried out industrially, and this method is similar to other methods such as the Pigeon method. This is a highly efficient method compared to the previous method.

In the electrothermal high-temperature reduction method, a closed single-phase Giraud furnace has conventionally been used, but the present inventors have discovered a new metal magnesium production apparatus using a closed three-phase AC immersion arc closed electric furnace. This was proposed in Japanese Patent Application No. 57-69535.

By the way, when electrothermal high-temperature reduction is performed using a single-phase Giraud furnace or a three-phase electric furnace according to the manufacturing apparatus proposed by the present inventors, the magnesium vapor generated in the furnace is sucked into the condenser, and one of the This caused the phenomenon that the heat seeped into the lining of the lid, furnace wall, and hearth in the electric furnace and gradually accumulated, resulting in deterioration of the insulation properties of the lining, increased heat dissipation, and poor power consumption.

An object of the present invention is to provide a metal magnesium manufacturing apparatus including an electric furnace that can prevent deterioration of power consumption rate due to permeation of magnesium vapor into the electric furnace lining. The above objects can be achieved by providing an apparatus according to the scope of the invention.

Next, the present invention will be explained in detail.

The electric furnace included in the metal magnesium manufacturing apparatus proposed by the present inventors in Japanese Patent Application No. 57-69535 is a three-phase AC immersion arc closed type electric furnace that can freely decompress; three electrodes are suspended in the furnace;
The lower part is made of artificial graphite; the electrode is vertically movable within a through hole provided in the lid of the electric furnace; A heat-resistant packing is interposed between the cylindrical body for preventing outside air from entering the furnace and for preventing lateral vibration during vertical movement of the electrode and the upper metal water-cooling conduit portion of the electrode; This closed electric furnace is characterized in that an inlet pipe for introducing an inert gas is connected to the cylindrical body in the gap between the body and the electrode.

As shown in Fig. 1, the lining structure of this electric furnace is such that a heat insulating material is laid on the bottom plate of a steel plate furnace shell 1, a fireproof insulation brick 2 is placed on top of the heat insulating material, and a fireproof brick 3 is placed on top of that. The parts that come into direct contact with the molten metal are lined with carbon blocks 4. In addition, a heat-resistant material 2 is placed in contact with the inner surface of the furnace shell 1.
However, a carbon block 4 is lined inside the molten metal contact area, and a refractory brick 3 is lined above the molten metal contact area. The furnace lid is made of refractory castable bricks 3
It is built with.

It has been found that when producing metallic magnesium using this electric furnace, the surface temperature of the furnace shell rises rapidly as the number of operating days passes, as shown in FIG. In order to elucidate the cause of this, the inventors dismantled the furnace body and investigated it, and found that magnesium was condensed and accumulated in various places within the furnace lining. In other words, it was found that the surface temperature of the furnace shell gradually increased as a result of the deterioration of heat retention.

Therefore, as shown in Figure 3, the present inventors installed a heat-resistant partition plate in the middle of the furnace lining layer to prevent magnesium vapor from permeating, thereby preventing the magnesium vapor generated in the furnace from entering the lining. As a result of preventing magnesium vapor from seeping into the outer lining layer by preventing seepage with the partition plate, the rise in the surface temperature of the furnace shell becomes relatively gradual as the number of days of operation increases, as shown in Figure 4. However, it was not possible to sufficiently suppress the rise in the surface temperature of the furnace shell and the rise in the electric power consumption rate.
That is, in this case as well, as a result of the furnace dismantling, it was found that magnesium condensation and accumulation existed around the outside of the partition plate.

The present inventors introduced an inert gas between the partition wall plate and the furnace shell, and set the gas pressure to a pressure that does not fall below the gas pressure of the atmosphere containing magnesium vapor in the closed electric furnace. The inventors have come up with the idea of preventing magnesium vapor from seeping into the outer periphery of the partition plate and the outer part of the partition plate. However, as mentioned above, in order to prevent the inert gas pressure between the bulkhead plate and the furnace shell from falling below the gas pressure in the furnace, it is necessary to use a considerable amount of inert gas, and the use of this gas is necessary. The inert gas that was removed flows into the furnace atmosphere,
This resulted in the concentration of magnesium vapor in the furnace being unnecessarily diluted.

Therefore, the present inventors divided the furnace shell and the partition plate facing it into one or more blocks, sealed the space between the furnace shell and the partition plate corresponding to each block including the lining, When an inert gas introduction pipe was installed for each of these blocks and inert gas was introduced,
The introduced gas is stagnant within each block,
The present invention was completed based on the finding that leakage into the furnace atmosphere can be completely or almost completely prevented.

Next, the present invention will be explained with reference to the drawings.

In Fig. 3, the electric furnace has a furnace shell 1 made of steel plate,
A heat insulating material is laid on the bottom plate of the steel plate furnace shell, on top of which a fireproof insulation brick 2 is built, and further above that a fireproof brick 3 is built, and the part that comes into direct contact with the molten metal is covered with carbon. Block 4 is lined. In addition, a heat insulating material 2 is provided in contact with the inner surface of the side wall plate of the furnace shell, and a refractory brick 3 is lined inside the heat insulating material 2, and a magnesium impermeable bulkhead plate 6 is provided on the inner side of the heat insulating material 2. The lower molten metal contact area is lined with carbon block 4, and the upper part is lined with refractory bricks. The furnace cover has a steel plate furnace shell lined with a castable refractory material 3, and a magnesium-impermeable partition plate 6 is provided approximately in the middle of the lining layer.

In FIG. 5, the electric furnace has a furnace shell 1 made of a steel plate, and a refractory heat insulating material 2 is lined in contact with the inner surfaces of the bottom plate and side wall plates of the steel plate furnace shell, and a magnesium vapor insulating material 2 is lined with the inner surface of the steel plate furnace shell. A permeable partition plate 6 is provided, and the space between the partition plate and the furnace shell is sealed separately into a furnace bottom portion and a furnace side wall portion. Further, a refractory material 3 is built inside the partition plate 6, and a carbon block 4 is lined in the portion that comes into direct contact with the molten metal. Further, a refractory material 3 is lined with a refractory material 3 in contact with the inner surface of the furnace lid of the steel plate furnace shell 1,
A magnesium vapor-impermeable partition plate 6 is provided inside thereof, and the space between the partition plate and the furnace shell of the furnace lid is sealed. Further, the inside of the partition plate is lined with a fireproof material 3.

In the furnace shell 1, inert gas introduction pipes 7 for introducing inert gas into the sealed portion between the furnace shell and the partition plate are arranged at the furnace lid, furnace side wall, and furnace bottom, respectively. has been done.

The partition wall plate 6 is mainly a metal plate, but
In addition, the dense partition wall board may be made of magnesium vapor impermeable material, and materials with low air permeability such as dense asbestos board, enamel board, impermeable graphite board, fiber-reinforced ceramic board, etc. can be used.

In the present invention, by providing the partition plate 6, it is possible to prevent magnesium vapor from penetrating into the heat insulating material and precipitating as fine metal magnesium powder, which would cause a significant deterioration of the heat insulating performance. Also,
The partition plate 6 is made of a metal plate such as an iron plate, and the space between the partition plate and the furnace shell is sealed to form an airtight chamber divided into one or more blocks, and the pressure inside the airtight chamber is reduced to within the electric furnace. That is, the inert gas can be supplied using the inert gas introducing pipe 7 so as to keep the pressure higher than the pressure inside the partition plate. As a result, even if, for example, a part of the bulkhead plate is damaged after long-term operation, diffusion of magnesium vapor into the heat insulation layer can be reliably prevented, and the pressure inside the airtight chamber can be reduced. By checking, you can definitely know if the partition plate is damaged. Furthermore, it was discovered that even if a part of the partition plate is damaged, the heat insulating material waste can be protected by supplying inert gas.

Maintaining the heat retention performance of the electric furnace for magnesium production of the present invention reduces heat radiation from the furnace shell,
It was found that the electric power consumption rate could be improved and, in addition, the operating period of the electric furnace could be significantly extended.

Next, an example of a method for manufacturing metal magnesium using the metal magnesium manufacturing apparatus of the present invention will be explained, and the effects of the lining structure of the electric furnace will be explained in Examples.

As raw materials, calcined dolomite (2CaO.MgO) and calcined magnesite (MgO) were used as magnesium oxide-containing substances, and ferrosilicon aluminum (Si = 50, A = 30, Fe = 20) was used as a reducing agent. About 3 pieces of calcined dolomite and calcined magnesite
The materials were mixed at a ratio of 1:1, and 20 to 25 parts of ferrosilicon aluminum was mixed with 100 parts of the mixture. The particle size of the raw material was approximately 1 to 15 mm.

When melting and reduction was performed using a 100 KVA three-phase AC closed type electric furnace according to the present invention, the inside of the electric furnace was made into an inert gas atmosphere, and electricity was applied while the raw materials were introduced to melt the raw materials. Next, the pressure inside the electric furnace is
The pressure was reduced to within 30-50 Terr and maintained there. Adjust the electrodes by raising and lowering them so that the power of each electrode is well balanced. The electrodes were raised and lowered automatically or manually depending on the load on each electrode.

After setting the electric power to a load of 65 KW, the raw materials were sequentially introduced. When raw material input is started, magnesium oxide is reduced to metal magnesium, and the metal magnesium turns into magnesium vapor. The magnesium vapor passed through the magnesium vapor outlet of the electric furnace, was introduced into a magnesium vapor condenser connected to the electric furnace, and was collected as liquid magnesium.

During operation, the electrode tip position and voltage were adjusted to maintain the molten metal temperature at approximately 1,600°C and to ensure that the raw materials in the electric furnace were completely melted. In addition, inert gas was flowed at a constant gas flow rate from the electrode through holes in the furnace cover and the raw material inlet to prevent blockages and electrical troubles caused by condensation of magnesium vapor in these areas.

After operating for a certain period of time, when slag and by-product medals accumulate in the electric furnace, and a certain amount of liquid magnesium accumulates in the magnesium condenser, raw material input is temporarily suspended, the electric furnace load is reduced, and the pressure inside the electric furnace is reduced. After returning to normal pressure with inert gas, the slag was discharged from the slag discharge port of the electric furnace, and liquid magnesium was taken out from the magnesium condenser.

At this time, when the electric furnace was returned to normal pressure, the furnace gas and dust were sucked through the furnace dust outlet to prevent clogging and contamination of the raw material input port and the electrode penetration part.

As soon as the slag and by-product metal in the electric furnace or the liquid magnesium in the magnesium condenser was discharged, the pressure in the electric furnace was returned to 30-50 Torr and operation continued.

As a result of continued operation as described above, in the electric furnace with the conventional lining structure (FIG. 1), the furnace shell surface temperature rose quite rapidly as the number of days of operation progressed, as shown in FIG. In this case, after 8 days of operation, the electric furnace was dismantled and the inside of the lining was investigated, and as shown in Figure 1, metallic magnesium condensation deposits 4 were observed in the lining layer.

Furthermore, in an electric furnace with a structure in which a partition plate is provided in the lining layer (Figure 3), the rise in the furnace shell surface temperature as the number of operating days passes is relatively gradual, as shown in Figure 4. However, when the lining was dismantled and investigated after 25 days of operation, metallic magnesium condensation was observed on the back side of the partition wall plate as shown in Figure 3.

Next, in the electric furnace (Fig. 5) in which the lining structure of the present invention is a closed type between the furnace wall and the partition plate,
As shown in Figure 6, there was no sudden rise in the furnace shell surface temperature, and the furnace shell surface temperature continued to be maintained at around 150°C during the 54 days of continuous operation, making it possible to continue operation. It was hot. In addition, the pressure in the airtight chamber between the partition plate and the furnace wall is the internal pressure of the electric furnace.
Compared to 30-50 Torr, the temperature was maintained at about 50-60 Torr.

As described above, according to the electric furnace lining structure of the present invention, unlike the conventional lining structure,
Magnesium vapor does not seep into the furnace lid, furnace walls, or hearth lining layer, so there is little damage to the lining, and the electric furnace maintains its heat retention properties over a long period of time, allowing for long-term continuous operation. It is expected that this will lead to great progress in the industrial production of magnesium metal.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of the conventional lining structure of a closed electric furnace for producing magnesium, Figure 2 is a diagram showing the relationship between the number of operating days of the electric furnace and the surface temperature of the furnace shell, and Figure 3 is a diagram showing the relationship between the number of operating days of the electric furnace and the surface temperature of the furnace shell. A vertical cross-sectional view of a lining structure provided with a partition plate, FIG. 4 is a diagram showing the relationship between the number of operating days of the electric furnace and the furnace shell surface temperature,
FIG. 5 is a longitudinal sectional view of a lining structure in which the space between the partition plate and the furnace shell is sealed, and FIG. 6 is a diagram showing the relationship between the number of operating days of the electric furnace and the surface temperature of the furnace shell. 1...Steel plate furnace shell, 2...Shamototsu-based insulation material, 3
...Alumina firebrick, 4...Carbon block,
5...Magnesium precipitated part in the lining, 6...
Partition plate, 7...Inert gas introduction pipe.

Claims (1)

[Scope of Claims] 1. In a metal magnesium production apparatus including a closed electric furnace for melting and reducing a magnesium oxide-containing substance using a reducing agent under reduced pressure, a lining layer provided inside the furnace shell of the electric furnace is provided. A magnesium vapor-impermeable bulkhead plate is provided along the furnace shell to prevent magnesium vapor from permeating the lining and reaching the furnace shell, and the pressure between the furnace shell and the bulkhead plate is controlled. A metal magnesium production device characterized by having an inert gas introduction conduit installed in the furnace shell. 2. Between the furnace shell and the partition plate of the electric furnace, the furnace shell and the partition plate facing it are divided into one or more blocks as necessary, and an inert gas is introduced into the furnace shell of each block. 2. Device according to claim 1, characterized in that it is provided with a conduit. 3. The magnesium vapor impermeable partition plate constituting the partition plate is any one of a metal plate, a dense asbestos plate, an enamel plate, an impermeable graphite plate, and a carbon fiber-reinforced ceramic plate. The device according to any one of scope 1 and 2.