JPS6134490B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention melts and reduces a substance containing magnesium oxide in an electric furnace using a reducing agent under reduced pressure, introduces the magnesium vapor generated at that time into a magnesium vapor condenser and condenses it, and then transfers the magnesium oxide to liquid magnesium from the condenser. The present invention relates to a method for continuously manufacturing magnesium metal, which involves continuous casting by discharging magnesium metal. 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. Although this method is highly efficient compared to the previous method, it still has various drawbacks in industrial production. Conventional equipment for manufacturing magnesium metal using the smelting reduction method consists of a single-phase electric furnace and a condenser for condensing magnesium vapor.Since the electric furnace is a single-phase fixed-electrode Giraud furnace, the electric power factor is poor and the capacity is large. In the case of a furnace, it is disadvantageous to operate with one furnace, and the operation is carried out by pairing three ordinary furnaces while maintaining electrical balance. For this reason, for example, when constructing a facility with an electric capacity of 10,000 KVA, three 3,300 KVA Giraud furnaces must be manufactured, and it is necessary to operate the three in parallel. Therefore, it is not only natural that the thermal efficiency will be much lower when operating with three 3,300 KVA furnaces than when operating with one 10,000 KVA furnace, but also, for example, with one 10,000 KVA furnace.
The drawback was that if one furnace failed, the remaining two furnaces would be forced to operate under unbalanced electrical conditions. By the way, the reason why only a single-phase fixed electrode type Giraud furnace has been conventionally used as an electric furnace for melting and reducing metallic magnesium is because the electric furnace can be easily sealed because the electrode is of a fixed type. However, as mentioned above, such electric furnaces have various drawbacks.
Since such electric furnaces had many drawbacks in terms of equipment and operational technology, the inventors of the present invention removed and improved these drawbacks and invented a three-phase closed immersion arc electric furnace. A patent application was filed under No. 57-69535. The apparatus of the invention is 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.
The electric furnace is a three-phase AC immersion arc closed type electric furnace that can freely depressurize; three electrodes hang down through the furnace lid of the electric furnace; the upper part of each electrode is a metal water-cooled conduit section. ,
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; The present invention relates to a metal magnesium production apparatus including a closed electric furnace in which an inlet pipe for introducing an inert gas into a gap between the body and the electrode is connected to a cylindrical body. Next, the magnesium vapor generated in the electric furnace is introduced into a magnesium vapor condenser, where it is condensed and solidified. When a predetermined amount of metallic magnesium has solidified in the condenser, the melting reduction in the electric furnace is interrupted, the condenser is separated from the connecting pipe from the electric furnace, and the solidified magnesium in the condenser is taken out. The solidified magnesium thus extracted was separately remelted, cast into a predetermined mold, and sold commercially. According to such conventional methods and devices, the operation had to be interrupted every time the magnesium in the condenser was taken out, and a considerable amount of thermal energy was required to further remelt the taken out magnesium. As a result of repeated research on the condenser, the present inventors came up with an improved condenser and its ancillary equipment that eliminates the various drawbacks of conventional condensers, and patented it in Japanese Patent Application No. 103104/1983. I applied. The apparatus of the invention melts and reduces a magnesium oxide-containing substance in an electric furnace using a reducing agent under reduced pressure,
In a metal magnesium manufacturing apparatus including a magnesium vapor condenser and its ancillary equipment for introducing and condensing the magnesium vapor generated at that time, the condenser has an inner wall made of a steel plate and an outer wall made of a steel plate,
A heating and cooling device and a heat insulating material are installed between the inner and outer walls, and the lower part of the condenser is the bottom part where condensed molten magnesium is accumulated; An apparatus for manufacturing magnesium metal, including a magnesium vapor condenser and ancillary equipment thereof, characterized in that: an exhaust port is provided for discharging magnesium; a stopper and an airtight casting chamber are provided in close contact with the exhaust port; It is something. By using the invented three-phase AC immersion arc closed electric furnace and magnesium vapor condenser, the above-mentioned drawbacks of the equipment have been eliminated and improved. However, in order to produce metallic magnesium using the above-mentioned equipment, there are obstacles in terms of operational technology. In other words, the magnesium vapor generated in the electric furnace condenses and adheres as soon as it reaches the low temperature part of the furnace, so magnesium vapor is deposited on the electrode penetration part of the furnace lid, inside or behind the lining between the three electrodes, etc. If the vapor penetrates and deposits, leakage between the electrodes will occur, causing major electrical troubles. Furthermore, if magnesium precipitates and dust generated in the furnace adhere to the electrode penetration part, this will impede the lifting and lowering of the electrode, accelerate damage to the airtight maintenance mechanism of the electrode part, and furthermore prevent electrical leakage between the electrode and the furnace lid. Cause. The dust generated in the electric furnace is normally introduced into the magnesium condenser together with magnesium vapor and furnace gas through the magnesium introduction pipe, but a part of the dust adheres to the introduction pipe and the introduction pipe is blocked. The company was forced to suspend operations. As a result of detailed research and repeated experiments regarding the various problems in the operational technology described above, the inventors of the present invention found that the above drawbacks can be eliminated by the configuration described in the claims. The manufacturing method has been perfected. That is, the present invention provides a method for producing metallic magnesium, in which a substance containing magnesium oxide is melted and reduced in an electric furnace using a reducing agent under reduced pressure, and the magnesium vapor generated at the time is introduced into a magnesium vapor condenser and condensed. (a) When melting and reducing a magnesium oxide-containing material and a reducing agent as raw materials under reduced pressure, a three-phase AC immersion arc closed electric furnace is used, and the three electrodes of the electric furnace are connected to each other. At least one gas selected from H ₂ , He, Ar, and N ₂ is introduced into the vicinity of the part of the electrode that penetrates the furnace lid to prevent magnesium vapor or dust from adhering to the part of the electrode that penetrates the furnace lid. Means for preventing; (b) When introducing the magnesium vapor generated in the electric furnace into the condenser together with the furnace gas,
Means for condensing magnesium vapor in the condenser and maintaining it in a liquid state while maintaining the interior of the condenser at a temperature that does not fall below the melting temperature of magnesium metal; (c) A predetermined amount of liquid magnesium is stored in the condenser. (d) When a predetermined amount of slag and by-product metal accumulates in the electric furnace, After returning the pressure in the electric furnace and condenser to normal pressure using at least one gas selected from H ₂ , He, Ar, and N ₂ , the slag exhaust installed at the bottom of the electric furnace is Means for discharging slag and by-product metal from the outlet; This invention relates to a method for producing metal magnesium by melting and reduction using an electric furnace, characterized by comprising a series of means (a) to (d) above. Next, the present invention will be explained in detail. Figure 1 is an overall equipment system diagram of the metal magnesium production apparatus used in the method of the present invention, and is a three-phase AC immersion arc closed electric furnace according to the aforementioned Japanese Patent Application No. 57-69535 and Japanese Patent Application No. 57-103104. and a magnesium steam condenser and its ancillary equipment. The electric furnace includes an electric furnace body 1, a furnace lid 15, and an electrode 9, and a discharge port 10 at the bottom of the furnace body 1 for discharging slag and by-product metal.
Moreover, a magnesium vapor introduction pipe 6 for introducing magnesium vapor into the condenser and a furnace gas discharge port separate from the introduction pipe are provided in the upper part. Three electrodes 9 are disposed in the furnace lid 15 in a delta shape so as to pass through the furnace lid, and the electrodes are movable up and down, and are completely isolated from the outside air. In addition, a raw material input pipe 11 is located in the center of the furnace lid.
is arranged, and a raw material storage container 12 is placed above it.
is provided. A magnesium steam condenser 2 is connected to the electric furnace via a magnesium steam introduction pipe 6,
The lower part of the condenser has an outlet for discharging liquid magnesium and an outlet for discharging dust and dross, and the outlet is provided with a stopper 16 that can be opened and closed. An airtight casting chamber 3 and an airtight chamber 4 are provided in close contact with the discharge port. The upper part of the condenser has an outlet for the residual gas after condensation and separation of the magnesium vapor, and a dust collector 5 is attached before that to remove dust contained in the residual gas. Further, a gas pipe 18 is provided in order to circulate and use the gas purified by the dust collector 5 as an inflow gas to the electric furnace, and a gas pipe 18 is provided in the middle of the pipe to suck and circulate the gas in the furnace. A gas suction pump 7, a gas holding container 8 for adjusting the flow rate of the gas, and a gas container 17 for replenishing the gas are attached. Further, even when gas is sucked from the furnace gas outlet disposed in the upper part of the electric furnace body 1, the gas suction pump 7 is provided with a pipe 19 so that the gas can be reused for circulation. A gas cooler 14 and a dust collector 3 are attached in the middle of the pipe 19. Note that this gas suction system and the gas suction system that passes through the magnesium condenser can be easily switched. Next, the operating method of the present invention will be explained. As raw materials, a magnesium oxide-containing substance, a reducing agent and, if necessary, a slag-forming agent are used to adjust the particle size to an appropriate particle size, and each is charged into the electric furnace either alone or in a mixed state after being blended in an appropriate amount,
It is melted and reduced. The magnesium oxide-containing material may be natural magnesia, seawater magnesia, dolomite, ferrochrome slag, or the like. A metal or alloy of silicon and/or aluminum is used as the reducing agent. When these are charged into an electric furnace and heated and melted, magnesium metal is produced according to the following reaction formula. 2MgO + Si = 2Mg + SiO ₂ 3MgO + 2A = 3Mg + A ₂ O _3The produced magnesium becomes steam and evaporates because the molten raw material in the electric furnace is at a high temperature of about 1600℃.
It is introduced into a magnesium vapor reducer where it is condensed and collected as liquid magnesium. SiO ₂ and A ₂ O ₃ shown in the above reaction formula become slag, but the slag that is produced is easily melted down and reduced, and the magnesium vapor produced by the reaction is easily generated and discharged from the electric furnace. In order to make this easy, it is necessary to have a composition with good fluidity. A slagging agent is added to give the slag the proper composition. The slag forming agent mainly contains A.
₂ O ₃ , CaO-containing substances, etc. are used, but a substance that provides an appropriate slag composition is selected and used depending on the magnesium-containing substance used. In performing the melting reduction of the above-mentioned raw materials and the condensation collection of magnesium vapor, the inside of the electric furnace and the magnesium vapor condenser are replaced with at least one gas selected from H ₂ , He, Ar, and N ₂ . The internal pressure (hereinafter referred to as the device internal pressure) is
30 to 100 Torr, usually in the range of 30 to 50 Torr. The pressure range of the magnesium production reaction according to the above reaction formula is very wide, and in fact, in the production of metallic magnesium using an electric furnace, the pressure range ranges from several tens of Torr, which is normally used, to a maximum of 1,500 Torr (US patent
Pressure ranges up to 3475162) have been used. The reason why the pressure ranges in the electric furnace and the magnesium vapor condenser are limited as above in the method of the present invention will be explained with reference to the phase diagram of metallic magnesium shown in FIG. As shown in FIG. 2, metallic magnesium has only a vapor phase and a solid phase, and no liquid phase exists at pressures below several Torr. In addition, a liquid phase exists above a few Torr and below 30 Torr, but the liquidus temperature range is narrow.
The operating conditions are difficult to efficiently condense magnesium vapor and maintain it in a liquid state, making it impractical. Conversely, as the pressure increases, the vaporization temperature (boiling point) of magnesium increases, so the magnesium vapor is repeatedly condensed and vaporized in the electric furnace before being introduced into the magnesium vapor condenser, reducing production efficiency. A phenomenon occurs in which condensation occurs near the magnesium steam introduction pipe that connects the electric furnace and the magnesium steam condenser, causing the system to become clogged. As a result of various experiments, it was found that the above-mentioned problems do not occur when the liquidus temperature range is about 200°C or more and the liquefaction temperature is about 1000°C or less. That is, the pressure in the electric furnace and in the magnesium steam condenser is 30~
It is necessary to set it within the range of 100 Torr, and within the range of 30 to 50 Torr is particularly preferable. Furthermore, the temperature inside the magnesium vapor condenser must be maintained within the range of 650 to 950°C due to the above pressure range. Since 650℃ is the melting point of magnesium,
Below that temperature, magnesium solidifies, and above 950°C, magnesium vapor evaporates without condensing. To adjust the temperature of the magnesium vapor condenser, a heating wire, a nonmetallic heating element, or a high frequency heating device can be used. Most of the magnesium vapor generated in the electric furnace is introduced into the magnesium vapor condenser together with the furnace gas and condensed, but some of it reaches the low temperature part of the electric furnace and immediately condenses and adheres to it.
If magnesium vapor penetrates into the electrode penetration part of the furnace cover or inside or behind the lining between the three electrodes and deposits and adheres, leakage between the electrodes will occur, causing major electrical problems. Furthermore, if magnesium precipitates and dust generated in the furnace adhere to the electrode penetration part, this will impede the lifting and lowering of the electrode, accelerate damage to the airtight maintenance mechanism of the electrode part, and furthermore prevent electrical leakage between the electrode and the furnace lid. Cause. According to the method of the present invention, in order to prevent such troubles, when melting and reducing the raw material, one of H ₂ , He, Ar, and N ₂ is released from each of the furnace cover through holes of the three electrodes. By allowing one type of gas to flow out, the above-mentioned problems can be easily prevented. At that time, during normal operation, that is, when the pressure inside the device is 30 to 50 Torr, the flow rate of the gas is 5 cm/cm at the linear velocity at the outlet of the furnace cover electrode through hole.
When the temperature is sec or more, precipitation of magnesium and adhesion of dust around the electrode penetration portion and around the electrode are no longer observed. However, the flow rate of the gas that can prevent the adhesion of magnesium and dust needs to be changed as the pressure inside the device changes.
For example, when the means set forth in claim 1 (d) is used, that is, when the pressure inside the apparatus is returned to normal pressure in order to discharge the slag and by-product metal accumulated in the electric furnace, or when the raw material is When a large amount of magnesium vapor is generated due to a large amount of magnesium vapor being introduced and the pressure inside the device increases, the force of the inflowing gas from the electrode through hole outlet is pushed back, causing magnesium to adhere to the electrode through hole. . On the other hand, if too much of the inflow gas is allowed to flow, if the suction capacity for the furnace gas and magnesium vapor is insufficient, the pressure inside the device will increase and pressure control will become difficult, and even if the suction capacity is sufficient,
Above a certain flow rate, the efficiency of the magnesium condenser decreases. As a result of experiments with various electric furnace volumes,
The upper limit of the inflow gas flow rate at which the above phenomenon does not occur is 120×Scm/linear velocity at the outlet of the electrode through hole.
It was found that it is expressed in sec (S is the furnace internal volume m ³ ). That is, the flow rate of the incoming gas is adjusted according to the pressure inside the apparatus within the range of 5 to 120 x Scm/sec at the linear velocity at the outlet of the electrode through hole of the furnace cover. Magnesium vapor generated in the electric furnace is sucked together with some dust and furnace gas and introduced into a magnesium vapor condenser, where the magnesium vapor is condensed and liquefied and separated, and the remaining gas is discharged from the upper part of the condenser. A part or all of this exhaust gas can be recycled and used as an inflow gas into the electrode through-hole portion of the lid of the electric furnace. This method makes it possible to greatly reduce the amount of relatively expensive gases used, such as H ₂ , He, and Ar, and in fact has great effects because only a small amount of gas lost during operation needs to be replenished. be. In order to circulate and use the in-furnace gas, the gas circulation system is provided with at least one selected from the group consisting of an in-furnace gas suction device, a suction gas cooler, a dust collector, and a suction gas holding container. It is possible to suction, cool, purify, and adjust the flow rate of gas in the furnace. According to this circulating use of gas in the furnace, if the pressure inside the device hardly changes, when the amount of incoming gas increases, the amount of exhaust gas also increases proportionally, so the intake and exhaust cannot be balanced. , operation becomes easier. Further, when the internal pressure of the apparatus changes, it can be adjusted by storing and discharging the gas into the suction gas holding container. Furthermore, an inflow gas for preventing adhesion of magnesium vapor and dust can be allowed to flow in not only through the furnace lid electrode through-hole but also through the raw material inlet of the electric furnace. By this means, it is possible to prevent the raw material input port from being blocked when the raw material input is temporarily interrupted. Next, the magnesium vapor generated in the electric furnace is normally introduced into the magnesium condenser, but during periods when a large amount of dust is generated, it is necessary to restart the electric furnace at the start or after returning the pressure inside the device to normal pressure. When slag and by-product metals are discharged, an in-furnace gas suction device is provided separately from the magnesium condenser, and the in-furnace gas containing a large amount of dust can be separately suctioned. In such cases, the dust components are approximately 85-95% MgO, 5-20% C,
CaO and A ₂ O ₃ are about 1%, and the main components are not fine powder generated from raw materials, but MgO + C → Mg
It was found that MgO and C produced by the reverse reaction of +CO accounted for most of the content. The fact that the above-mentioned reverse reaction occurs in an Ar atmosphere means that
Forward reaction of the above reaction formula that generates CO gas
MgO+C→Mg+CO must occur. Furthermore, as is well known, the forward reaction in the above reaction formula occurs at temperatures above 1800°C, so slag builds up around the graphite electrode at the start of operation or after discharging slag and by-product metals from the electric furnace. It is thought that this occurs only when local heating is performed by arc heat when it is not sufficiently formed. The present inventors confirmed the above phenomenon in actual operation, and found that during the period when blockage on the magnesium steam condenser side is expected, an in-furnace gas suction device installed in a separate system from the condenser and its auxiliary equipment By operating the magnesium vapor condenser and drawing it into the condenser only when highly pure magnesium vapor is generated, excluding such times, it is possible to reduce blockage or contamination of the magnesium vapor condenser and its ancillary equipment. Long-term operation becomes possible. Further, the in-furnace gas suction device, suction gas holding container, etc. may be used alone or in common, as shown in FIG. 1, for suctioning from the magnesium vapor condenser side and for suctioning from another system. After the internal pressure of the liquid magnesium device stored in the lower part of the magnesium condenser is returned to normal pressure, the discharge port of the condenser can be opened and the liquid can flow out for casting. A chamber is provided, a mold is installed in the chamber, the pressure is reduced in the airtight casting chamber, liquid magnesium is flowed out at almost the same pressure as the inside of the device, and the liquid magnesium is cast, thereby allowing independent operation independent of the operation of the electric furnace. can do. Note that a continuous casting device can also be used in casting. In the magnesium condenser, dust and a slag-like component usually called dross accumulates, but when a certain amount of the dust and dross has accumulated, after liquid magnesium is discharged from the outlet, A separate dross receiver may be installed to discharge the dust and dross, or a separate dross discharge port may be provided at the bottom of the condenser to discharge the dust and dross. In the latter case, it is preferable to provide an airtight chamber that can accommodate the dross receiver in close contact with the dross outlet. Next, when electric furnace operation continues, SiO ₂ , A
Slag mainly composed of ₂ O ₃ and by-product metal (mainly low-grade Si ferrosilicon) after consuming Si and A accumulate at the bottom of the electric furnace. When discharging the slag and by-product metal, the pressure inside the electric furnace is returned to normal pressure using at least one gas selected from H ₂ , He, Ar, and N ₂ . Open the discharge port provided at the bottom of the electric furnace to discharge. At that time, it is possible to stop the gas flowing into the electric furnace, but the pressure inside the electric furnace will be slightly reduced and there is a risk of outside air entering from the exhaust port, so the electric It is safer to maintain normal pressure while allowing gas to flow into the furnace. Further, when the pressure is set to normal pressure, the amount of dust generated increases, so in order to prevent the dust from entering the magnesium condenser, the furnace gas can be sucked in from the condenser and another furnace gas outlet. . As shown above, when the pressure inside the device exceeds 100 Torr, the gas inside the furnace is sucked through a separate system without passing through the magnesium condenser, and during normal operation (30 to
100 Torr), the quality of the produced metallic magnesium is improved by introducing the furnace gas and magnesium vapor into the magnesium condenser and condensing it.On the other hand, as the pressure inside the electric furnace increases, magnesium vapor is generated. Since the amount decreases, the loss of magnesium itself is small, and the effect on the magnesium yield is minimal. Next, examples of the present invention will be described. Example 1 Calcined dolomite (2CaO.MgO) and calcined magnesite (MgO) were used as raw materials containing magnesium oxide, and ferrosilicon aluminum (FeSiA) was used as a reducing agent. The raw material composition and blending ratio of each are shown in Table 1.
The particle size of the raw material is about 1 to 15 mm.

【table】

[Table] 150KVA three-phase AC closed electric furnace (electrode diameter 127
mmφ, furnace inner diameter 800 mmφ), the inside of the electric furnace was made into an argon gas atmosphere, and electricity was applied while charging the raw materials to melt the raw materials. Next, the pressure in the electric furnace and magnesium vapor condenser was reduced to a range of 30 to 50 Torr, and while maintaining the pressure, the mixed raw materials were successively introduced and melted. Until 12 hours after the start of operation, the gas in the furnace is sucked through the magnesium condenser and a separate gas outlet to prevent large amounts of dust from being introduced into the magnesium condenser etc. at the beginning of operation. The flow rate of the argon gas flowing into the electric furnace was approximately 30 cm/sec. After 12 hours, when switching to normal operation (operation in which furnace gas and magnesium vapor are sucked and introduced into the magnesium condenser at an internal pressure of 30 to 100 Torr), the inflow gas flow rate into the electric furnace is reduced to 20 cm. /sec, and the magnesium vapor produced by reducing magnesium oxide was introduced into the magnesium condenser together with the furnace gas, and the magnesium vapor was condensed and collected as liquid magnesium. During this operation, the temperature of the molten metal in the electric furnace was maintained at approximately 1600°C, and the temperature inside the magnesium steam condenser was adjusted and maintained at approximately 800°C. When a certain amount of liquid magnesium accumulates at the bottom of the magnesium vapor condenser after a certain period of operation,
Flowing the liquid magnesium into an airtight casting chamber,
Cast directly into a mold. In addition, when dust or dross accumulates in the magnesium vapor condenser,
The dross was discharged into a dross receiver installed in an airtight room. When the electric furnace continues to operate and a certain amount of slag and by-product metal accumulates in the electric furnace, the pressure inside the equipment is returned to normal pressure using argon gas, and at the same time, the pressure is returned to normal pressure from the magnesium condenser and another gas outlet. Gas is sucked into the furnace, and the inflow gas flow rate from the electrode through hole is set to approximately 30%.
cm/sec, slag and by-product metal were discharged from the electric furnace. After the discharge of the slag and by-product metals was completed, the pressure inside the apparatus was returned to 30 to 100 Torr to restore normal operation. As a result of continuing the operation as described above, even after 8 days of operation, there was no precipitation of magnesium vapor or adhesion of dust to the electrode through-hole portion of the furnace lid, and stable operation for a long period of time was possible. Furthermore, by not introducing furnace gas into the magnesium condenser at the beginning of operation and at normal pressure, the number of times dust and dross are discharged from the magnesium condenser is about 100% compared to when furnace gas is always introduced into the magnesium condenser. 1/2
decreased to Moreover, when comparing the two above, it was clearly seen that the quality of the produced metallic magnesium was improved as shown in Table 2.

[Table] Comparative Example 1 In the same operation as in Example 1, when the flow rate of argon gas flowing into the electric furnace from the electrode through hole in the furnace lid during normal operation was 3 cm/sec, magnesium vapor deposits were formed around the electrode. Adhesion was observed, and about 3 days later an electrical leakage phenomenon was observed and the electric furnace operation was stopped.
As a result of dismantling the equipment, an increase in the amount of dust accumulated in the magnesium condenser was also observed, necessitating an operation to remove the magnesium deposits and dust. Example 2 Using a 150KVA three-phase AC closed electric furnace and the same raw materials as in Example 1, the temperature of the hot water in the electric furnace was approximately
1600℃, the temperature inside the magnesium condenser is about 800℃
The operation was carried out with the adjustment maintained. The pressure inside the device is maintained at 30 to 50 Torr during normal operation.
Argon gas was used as the gas in the furnace and the inflow gas from the electrode through hole, and the gas flow rate was normally 20 cm/sec at the exit of the electrode through hole, and was increased accordingly if the pressure inside the device increased. . During normal operation, the magnesium vapor generated in the electric furnace is sucked into the magnesium condenser together with the furnace gas, only the magnesium is condensed and separated, and some of the remaining gas and dust are discharged from the upper part of the condenser and then collected. After the dust in the residual gas was removed using a vessel, it was recycled and used as an inflow gas from the electrode through hole to the electric furnace. In addition, since the start of operations, 12
When slag and by-product metal accumulate in the furnace after continuous operation for a certain period of time, and when the inside of the equipment is returned to normal pressure to discharge it, the inside of the furnace is discharged from the magnesium condenser and another gas outlet. The gas was sucked, dust removed and cooled in the same manner, and then recycled and used. In addition, when raw material input is temporarily interrupted as necessary, for example, when discharging slag or by-product metal, argon gas is similarly flowed into the electric furnace from the raw material input port to prevent blockages caused by magnesium vapor and dust adhesion. Prevented. When using this argon gas circulation, as shown in Figure 1, the suction pump port of the system for suctioning the furnace gas is shared with the magnesium condenser system, and also serves as the gas inflow into the electric furnace. It has become easier to maintain a balance between the gas constantly flowing into the electric furnace and the exhaust gas. In addition, when switching between the pressure during normal operation (30 to 100 Torr) and normal pressure, a gas holding container 8 provided in the middle of the gas circulation system is used, and when reducing the pressure, excess gas is held in the container, When increasing the pressure, it was regulated by releasing it. Due to the above operations, there was almost no need for new use of argon gas during operation, and the use of expensive argon gas had almost no effect on manufacturing costs. The following describes the casting of liquid magnesium and the discharge of slag and by-product metal from the electric furnace in Example 1.
It was carried out and operated in the same manner. As a result, the adhesion of magnesium vapor deposits and dust to the electrode penetration parts of the furnace cover was prevented, and the purity of metallic magnesium was improved. Example 3 Using a 150KVA three-phase AC closed electric furnace and the same raw materials as in Example 1, the temperature of the molten metal in the electric furnace was approximately
1600℃, the temperature inside the magnesium condenser is about 800℃
The operation was carried out with the adjustment maintained. The pressure inside the device is maintained at 30 to 100 Torr during normal operation.
Argon gas was used as the in-furnace gas and the inflow gas from the electrode through-hole, and the gas flow rate was normally 40 cm/sec at the exit of the electrode through-hole. The magnesium vapor generated in the electric furnace is sucked into the magnesium condenser together with the furnace gas, and only the magnesium is condensed and separated, and some of the remaining gas and dust are discharged from the upper part of the condenser, but during normal operation or slag, In order to discharge by-product metals, the furnace gas and magnesium vapor were discharged through the magnesium condenser regardless of when the pressure was returned to normal. In this case, since all the dust generated in the electric furnace is introduced into the magnesium condenser, the number of times dust and dross are discharged from the condenser has increased.
That is, each time liquid magnesium was discharged from the condenser and cast, dust was discharged, and compared to Examples 1 and 2, the cast magnesium metal had more dirt and was inferior in quality. Additionally, it was necessary to clean the inside of the condenser about once every two days. Table 2 shows examples of the quality of magnesium metal produced by the method of the present invention, which was equivalent to or better than commercially available products even without remelting as in the conventional method. Table 3 summarizes the results of operation according to the method of the present invention.

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is an overall equipment system diagram of a metal magnesium manufacturing apparatus used in the method of the present invention, and FIG. 2 is a state diagram of metal magnesium. 1... Electric furnace furnace body, 2... Magnesium vapor condenser, 3... Airtight casting chamber, 4... Airtight chamber, 5... Dust collector,
6... Magnesium vapor introduction pipe, 7... Gas suction pump, 8... Gas holding container, 9... Electrode, 10... Slag discharge port, 11... Raw material input port, 12... Raw material storage container, 13... Dust collector, 14... Gas cooler , 15... Furnace cover, 16... Stopper, 17... Gas container, 18...
Gas piping, 19...Gas piping.

Claims (1)

[Scope of Claims] 1. A method for producing metallic magnesium, in which a substance containing magnesium oxide is melted and reduced in an electric furnace using a reducing agent under reduced pressure, and the magnesium vapor generated at the time is introduced into a magnesium vapor condenser and condensed. (a) When melting and reducing a magnesium oxide-containing material and a reducing agent as raw materials under reduced pressure, a three-phase AC immersion arc sealed electric furnace is used, and the three electrodes of the electric furnace are connected to each other. At least one gas selected from H ₂ , He, Ar, and N ₂ is introduced into the vicinity of the part of the electrode that penetrates the furnace lid to prevent magnesium vapor or dust from adhering to the part of the electrode that penetrates the furnace lid. Means for preventing; (b) When introducing the magnesium vapor generated in the electric furnace into the condenser together with the furnace gas,
Means for condensing magnesium vapor in the condenser and maintaining it in a liquid state while maintaining the temperature in the condenser at a temperature not lower than the melting temperature of magnesium metal; (c) A predetermined amount of liquid magnesium is stored in the condenser. (d) When a predetermined amount of slag and by-product metal accumulates in the electric furnace, After returning the pressure in the electric furnace and condenser to normal pressure using at least one gas selected from H ₂ , He, Ar, and N ₂ , the slag exhaust installed at the bottom of the electric furnace is A method for manufacturing magnesium metal by smelting and reduction in an electric furnace, characterized by comprising a series of means (a) to (d) above: means for discharging slag and by-product metal from an outlet; 2. The manufacturing method according to claim 1, wherein in the means (a) to (c), the pressure in the electric furnace and the magnesium vapor condenser is set to 30 to 100 Torr. 3. The temperature in the magnesium vapor condenser is maintained within a temperature range of 650 to 950°C using a heating wire, a nonmetallic heating element, or a high frequency heating device. The manufacturing method described in any of the above. 4. Claims 1 to 4 are characterized in that in the means (a) to (d) above, the furnace gas after condensing the magnesium vapor is circulated and used as the inflow gas of the furnace lid penetrating portion of the electrode. The manufacturing method according to any of Item 3. 5. When circulating the furnace gas, the circulation system is equipped with at least one selected from a furnace gas suction device, a suction gas cooler, a dust collector, and a suction gas holding container to suck the furnace gas. 5. The manufacturing method according to any one of claims 1 to 4, characterized in that cooling, purification, and flow rate adjustment are performed. 6 In the means of (a) and (d) above, at least one gas selected from H ₂ , He, Ar, and N ₂ is flowed into the raw material input port of the electric furnace, and magnesium vapor or dust is produced. The manufacturing method according to any one of claims 1 to 5, characterized in that clogging of the raw material input port due to adhesion is prevented. 7 In the means of (a) and (d) above, in addition to the magnesium vapor inlet that introduces the magnesium vapor generated in the electric furnace into the condenser, the in-furnace gas and dust outlet provided on the side wall of the electric furnace The manufacturing method according to any one of claims 1 to 6, characterized in that the in-furnace gas and dust are sucked to prevent clogging of the inlet. 8 In the means of (a) and (d) above, the outflow linear velocity V of the gas is set to 5 cm/sec or more at the part where the electrode passes through the furnace lid or the raw material input port, and the maximum linear velocity V is 120 x Scm/sec.
The manufacturing method according to any one of claims 1 to 7, characterized in that sec (S is the furnace internal volume; m ³ ). 9 In the above method (c), when liquid magnesium is discharged from the discharge port provided at the bottom of the condenser, the airtight casting chamber connected to the discharge port is filled with H ₂ , He, Ar, and N ₂ . Any one of claims 1 to 8, characterized in that the casting is performed in at least one selected atmosphere, and is cast into a mold provided in the airtight casting chamber under normal pressure or reduced pressure and solidified. The manufacturing method described in Crab. 10 In the means (d) above, when discharging slag and by-product metal, H ₂ , He,
At least one selected from Ar, N ₂
Claims 1 to 3, characterized in that a seed gas is introduced and discharged while maintaining the pressure at normal pressure.
The manufacturing method according to any of Item 9.